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. 2021 Oct 13;16(10):e0258520. doi: 10.1371/journal.pone.0258520

Longitudinal associations between hearing aid usage and cognition in community-dwelling Japanese older adults with moderate hearing loss

Saiko Sugiura 1,2,*, Yukiko Nishita 3, Yasue Uchida 2,4, Mariko Shimono 2, Hirokazu Suzuki 2, Masaaki Teranishi 2,5, Tsutomu Nakashima 2,6, Chikako Tange 3, Rei Otsuka 3, Fujiko Ando 3,7, Hiroshi Shimokata 3,8
Editor: Masaki Mogi9
PMCID: PMC8513843  PMID: 34644353

Abstract

We investigated the associations between hearing aids (HA) and the maintenance of cognitive function among community-dwelling older adults with moderate hearing loss. A total of 407 participants aged 60 years or older with moderate hearing loss were recruited from the National Institute for Longevity Sciences, Longitudinal Study for Aging (NILS-LSA). Moderate hearing loss was defined as a pure-tone average of 40–69 dB at 500, 1000, 2000, and 4000 Hz of the better ear, according to the definition proposed by the Japan Audiological Society. Cognitive function was evaluated using the four subtests of the Japanese version of the Wechsler Adult Intelligence Scale-Revised Short Forms (WAIS-R-SF): Information, Similarities, Picture completion, and Digit Symbol Substitution (DSST). A longitudinal analysis of 1192 observations with a mean follow-up period of 4.5 ± 3.9 years was performed. The HA use rate at any time during the follow-up period was 31.4%, and HA users were significantly younger (t-test, p = 0.001), had worse hearing (p < .0001) and higher education (p = 0.001), participated more frequently in the survey (p < .0001), and were less depressed (χ2 test, p = 0.003) than the older adults not using HA. General linear mixed models consisted of the fixed effects of HA use, follow-up time, and an HA use × time interaction term adjusted for age and pure-tone average thresholds at baseline, sex, education, and other possible confounders. HA use showed significant main effects on the scores for Picture completion and DSST after adjustment; scores were better in the HA use group than in the no HA use group. The HA use × time interaction was significant for the Information score (p = 0.040). The model-predicted 12-year slope with centralizing age indicated that the no HA use group showed greater decline over time on Information scores than did HA use group. The slopes did not differ between HA users and non-users for the Similarities, Picture completion and DSST. In conclusion, HA use may have a protective effect on the decline in general knowledge in older adults with moderate hearing loss.

Introduction

The proportion of older adults in the global population has been increasing with an increase in the average life span, and Japan is one of the countries with the highest aging populations. The global population of older adults is expected to reach 1.4 billion by 2030 and 2.1 billion by 2050 [1]. Thus, it is crucial to maintain healthy aging and decrease the burden of aging. Hearing and cognitive impairments are the most common chronic conditions in older adults. Approximately, one-third of older adults may show hearing impairments [2], while there are over 50 million older adults with dementia worldwide [3].

Many studies have shown a link between hearing impairment and cognitive problems, and some meta-analyses have also shown that hearing impairment is one of the most effective risk factors for dementia or cognitive decline [4, 5]. We investigated whether baseline hearing status was associated with the degree of cognitive change assessed with four neuropsychological subtests during a 12-year follow-up in a Japanese older population, and reported that the rate of change in cognitive performance over time differed significantly depending on the presence or absence of hearing impairment [6].

Hearing aids (HA) are the primary management option for hearing loss, and some studies have reported that the use of HA may prevent cognitive decline in adults with hearing loss [7–9]. However, HA use was found to show no significant preventive effects on cognitive decline in a meta-analysis [10]. In a recent study, Glick et al. suggested that clinical intervention with well-fit HA may promote cortical organization and functioning and provide cognitive benefits beyond the known benefits of HA use on communication [11]. They investigated changes in the high-density electroencephalogram in the group with mild to moderate hearing loss, and showed that use of well-fit amplification reversed cross-modal recruitment of the auditory cortex for visual processing over the subsequent 6 months.

However, many older adults with hearing loss may not use HA. While some patients with hearing loss can use HA without problems, other may choose to not use them or may stop using them because of unrealistic expectations, unsatisfactory sound quality, poor hearing aid handling skills, discomfort, problems with support, psychosocial problems, and other reasons [12]. The HA-ownership rate varies by nation; for example, the rate of HA owners among hearing impaired people in Denmark was up to 50% [13], while the rate in Japan was under 15% [14]. This finding implies that the usage rate may be even lower. The WHO recommended HA for moderate (41–60 dB) and severe (61–80 dB) hearing loss; however, the HA-ownership rate among community-dwelling adults in Japan with over 40 dB hearing loss was 39.0% [15]. There are several reasons for the low HA usage rate, which include the high cost of HA, embarrassment related to the use of HA or the hearing impairment itself, lack of proper information or guidance for wearing HA, and low satisfaction with HA [16]. The lack of subsidies may be one of the reasons for the low ownership of HA in Japan. In Japan, the public HA subsidy system is generally used only for people with severe hearing loss of 70 dB or more.

A thorough understanding of the actual effectiveness of hearing interventions is essential, even in cases with moderate hearing loss. We had previously reported that regular HA use showed a protective effect against cognitive impairment assessed using the Mini-Mental State Examination in those with moderate hearing loss [17]. Thus, we aimed to clarify whether there were longitudinal differences in cognitive function between the HA use group and the no HA use group in community-dwelling older adults with moderate hearing loss.

Materials and methods

Participants

The participants were enrolled from the National Institute for Longevity Sciences, Longitudinal Study of Aging (NILS-LSA). The NILS-LSA is a community-based random sample study of aging and age-related diseases that represents the total Japanese population of middle-aged and older adults. The lifestyle of residents of this area is typical of most individuals in Japan, and the participants are sex- and age-stratified. Participants aged 40–79 years at baseline (Wave 1: 1997–2000) were followed up every 2 years. Age and gender-matched random samples equivalent to the number of dropout participants were recruited, except for participants aged over 79 years, and male and female participants aged 40 years were also newly recruited every year. The examination intervals were as follows: Wave 2: 2000–2002, Wave 3: 2002–2004, Wave 4: 2004–2006, Wave 5: 2006–2008, Wave 6: 2008–2010, and Wave 7: 2010–2012. A reduced follow-up study was performed in Wave 8 from 2013 to 2016. Details of the NILS-LSA have been published elsewhere [18], and the protocol and basic data are provided on the relevant in web page (https://www.ncgg.go.jp/cgss/english/department/nils-lsa/). NILS-LSA is one of the largest cohort studies in Japan that assessed pure-tone audiometry.

From all the participants in the NILS-LSA, we included those who had moderate hearing loss in this study. The baseline of this study was the time when the participants first showed moderate hearing loss (details are explained below) in any wave. The exclusion criteria were (a) age under 60 years at baseline (N = 25), (b) a history of dementia at baseline (N = 12), and (c) absence of any essential information, such as the results of the cognitive assessment or the data for confounders at baseline (N = 56). We did not exclude participants who had otological diseases or adjust history of otological diseases as confounder because missing data was not small (N = 50). Study profile and the final sample are presented in Fig 1 and Table 1. Time 1 represented the baseline, and Time 2–8 referred to the subsequent waves. For example, if the participant had moderate hearing loss in Wave 2 and participated in Wave 4 and Wave 6, Wave 4 was Time 3, and Wave 6 was Time 5. Thus, a total of 1192 observations from 407 participants who with moderate hearing loss were used for the analysis. The mean follow-up period was 4.5 ± 3.9 years, and the average number of measurements was 2.9 ± 1.7. There was a total of 128 participants who used HA in this study. Of those, there were 66 participants who had moderate hearing loss and used HA since their first participation, however, the time at which they had moderate hearing loss and began using HA was unknown. The average time interval between baseline and report of HA use was 5.9 ± 3.1 years in the other 62 HA users.

Fig 1. Study profile.

Fig 1

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Table 1. Number of participants and durations of the follow-up periods from baseline.

N Follow-up years from baseline HA user, N %
Baseline (Time 1) 407 66 16.2
Time 2 302 2.2 ± 0.4 70 23.2
Time 3 200 4.2 ± 0.5 50 25.3
Time 4 126 6.4 ± 0.5 45 35.7
Time 5 80 8.4 ± 0.6 32 40.0
Time 6 47 10.5 ± 0.7 26 55.3
Time 7 23 12.5 ± 0.8 14 60.9
Time 8 7 15.5 ± 0.7 3 42.9
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The study population consisted of 407 participants with moderate hearing loss (pure-tone average threshold level of the better hearing ear at frequencies of 500, 1000, 2000, and 4000 Hz: PTABHE ≥ 40 and < 70 dB).

Evaluations

Cognitive assessment

Cognitive function was assessed using the Japanese version of the Wechsler Adult Intelligence Scale-Revised Short Forms (WAIS-R-SF) [19]. The WAIS-R-SF consists of four subtests; Information, Similarities, Picture completion, and Digit Symbol Substitution (DSST) [20]. The Information subtest assesses general knowledge by asking 29 general knowledge questions (possible scores range from 0 to 29). The Similarities subtest assesses logical abstract thinking by asking the participants to state the similarities among 14 items (possible scores range from 0 to 28). The Picture completion subtest assesses visual perception and memory by asking participants to point out the missing elements in a series of drawings (possible scores range from 0 to 21). The DSST assesses processing speed by asking participants to write as many symbols as possible that correspond to a given number in 90 s (possible scores range from 0 to 93). Trained examiners (clinical psychologists or psychology graduate students) administered the test to each participant according to the standard instructions. The examiners spoke to the participants loudly, clearly, and slowly enough to understand. If the participants had HA, they wore them. Participants who could not understand the conversation adequately despite the above conditions were not included in the test.

Hearing assessment and other measures

Air-conduction pure-tone audiometry was performed in a sound-proof booth by trained technicians using a diagnostic audiometer (AA-73A and AA-78; Rion, Tokyo, Japan). The pure-tone average threshold levels at four frequencies (500, 1000, 2000, and 4000 Hz) with the better hearing ear (PTABHE) were used to determine hearing status. PTABHE ≥ 40 and < 70 dB was defined as moderate hearing loss according to the definition of the Japan Audiological Society. We defined hearing status according to the WHO hearing impairment grade [21] in our previous studies [6, 17]; however, the WHO recently proposed a new grading system categorizing hearing impairment as follows; normal (< 20 dB), mild (20–34 dB), moderate (35–49 dB), moderately severe (50–64 dB), severe (65–79 dB), and profound (≥ 80 dB) based on the average threshold at 500, 1000, 2000, and 4000 Hz [22]. In Japan, the quadrant method ((500 Hz + 1000 Hz + 1000 Hz + 2000 Hz)/4) has been used for the diagnosis of hearing impairment for a long time, and if the hearing in both ears is 70 dB or more, or if the hearing in one ear is 90 dB or more and that in the other ear is 50 dB or more, the patient is diagnosed with an authorized hearing disability and can receive public assistance such as hearing aid subsidy. Under this background, the Japan Audiological Society defined moderate hearing impairment as a 40–69 dB average threshold of 500, 1000, 2000, and 4000 Hz. Thus, we conducted a study based on the diagnostic criteria of the Japan Audiological Society.

Participants answered a series of questionnaires, which included detailed assessments of their medical history and lifestyle. All participants were asked about their HA usage, and the possible answers were “always use”, “sometimes use”, “have a hearing aid, but never use it”, and “have no hearing aid”. The “always use” and “sometimes use” responses were considered to indicate HA usage. The responses for medical histories of dementia, hypertension, dyslipidemia, diabetes, ischemic heart disease, and stroke were categorized into “yes” or “no”. Participants were also asked about their household income, occupation, marital status, smoking status, and education. Household income was divided into “greater than or equal to 5,500,000 yen/year” or “less than 5,500,000 yen/year.” Occupation was divided into “having an occupation” or “unemployed.” Marital status was divided into “married” or “unmarried.” Smoking status was classified as “non-smoker” or “ex- or current smoker.”

The participants’ height and weight were measured, and obesity was defined as a body mass index greater than 25.0 kg/m2. The Center for Epidemiologic Studies Depression Scale (CES-D) [23] was also assessed, and depressed mood was defined by a CES-D score over 15.

Ethical approval

The study protocol complied with the Declaration of Helsinki and was approved by the Committee on Ethics of Human Research of the National Institute for Longevity Sciences (No. 1369). Written informed consent was obtained from all participants.

Statistical analysis

Categorical variables are displayed as counts and percentages, and continuous variables are presented as mean ± standard deviation (SD) unless otherwise stated. A t-test was used to evaluate the differences in continuous variables, and the chi-square test was used to evaluate differences in categorical variables in univariate analysis of baseline data between groups with and without HA.

General linear mixed models were used to evaluate the associations between HA use and cognitive changes during the follow-up period. This model is similar to ordinary regression analysis, but because it allows correlation between the observations, it can handle missing data in repeated measurements more appropriately [24]. In this study, the model included fixed terms for the intercept which was baseline performance with a value of zero for all predictors, time (in years since baseline), HA use (no HA use at any time of follow-up period, or HA use), and the HA use × time interaction term. Covariates were age, sex, education, marital status, occupation, income, depressed mood, smoking status, obesity, and history of disease (hypertension, diabetes, dyslipidemia, ischemic heart disease and stroke) at baseline. The age at baseline was centered at the average age of the baseline for efficient convergence. We also calculated the random effects of intercept and slope using an unstructured covariance matrix, and predicted 12-year changes by considering potential confounders to make it easier to compare with our previous study [6]. In addition, the analyses excluding Time 6–8 were performed because the follow-up rates were under 20% from Time 5.

Statistical analyses were conducted using the Statistical Analysis System (SAS) version 9.3 (SAS Institute, Cary, NC, USA). The two-sided significance level was set at p < 0.05.

Results

The baseline characteristics of the participants are presented in Table 2. Among 407 older adults with moderate hearing loss, 279 (68.6%) did not use HA during the follow-up, and 128 (31.4%) used HA. The participants who used HA were significantly younger, had worse in PTABHE and higher education, and showed less depressed mood than non-users. The number of measurements, that is, the frequency of participation in the survey, was significantly higher among HA users. The baseline scores for Picture completion and DSST were significantly higher in HA users than in non-users, although there were no significant differences in Information and Similarities scores.

Table 2. Participant characteristics at baseline.

Total No hearing aid usage Hearing aid users p-value
N 407 279 128
Number of measurements 2.9 ± 1.7 2.6 ± 1.5 3.7 ± 1.9 < .0001
Age, years 74.6 ± 5.3 75.2 ± 5.2 73.4 ± 5.4 0.001
PTABHE, dB 45.0 ± 5.8 43.6 ± 4.5 48.2 ± 7.1 < .0001
Education, years 10.5 ± 2.5 10.2 ± 2.5 11.1 ± 2.5 0.001
Sex, male (n, %) 279 (68.6%) 175 (62.7%) 90 (70.3%) 0.136
Marital status, married (n, %) 327 (80.3%) 220 (78.9%) 107 (83.6%) 0.264
Occupation, employed (n, %) 89 (21.9%) 61 (21.9%) 28 (21.9%) 0.998
Hypertension (n, %) 186 (45.7%) 123 (44.1%) 63 (49.2%) 0.335
Dyslipidemia (n, %) 86 (21.1%) 55 (19.7%) 31 (24.2%) 0.301
Diabetes (n, %) 61 (15.0%) 43 (15.4%) 18 (14.1%) 0.723
Ischemic heart disease (n, %) 51 (12.5%) 37 (13.3%) 14 (10.9%) 0.511
Stroke (n, %) 35 (8.6%) 27 (9.7%) 8 (6.3%) 0.252
Smoker or ex-smoker (n, %) 217 (53.3%) 146 (52.3%) 71 (55.5%) 0.556
Obesity (n, %) 75 (18.4%) 53 (19.0%) 22 (17.2%) 0.662
High income (≥5,500,000 yen/year) (n, %) 111 (27.3%) 69 (24.7%) 42 (32.8%) 0.089
Depressed mood (>15 CES-D score) (n, %) 76 (18.7%) 63 (22.6%) 13 (10.2%) 0.003
Information (maximum score, 29) 12.9 ± 5.5 12.8 ± 5.7 13.2 ± 5.3 0.542
Similarities (maximum score, 28) 10.1 ± 5.4 10.0 ± 5.4 10.5 ± 5.4 0.377
Picture completion (maximum score, 21) 9.5 ± 3.9 9.1 ± 4.0 10.3 ± 3.8 0.006
Digit symbol substitution (maximum score, 93) 38.1 ± 10.9 37.0 ± 10.7 40.5 ± 11.0 0.003
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p-values were calculated using the chi-square test for categorical values and t-test for continuous values.

PTABTE: pure-tone average threshold level of the better ear at frequencies of 500, 1000, 2000, and 4000 Hz

CES-D: The Center for Epidemiologic Studies Depression Scale

Table 3 shows the results of multivariable analyses to evaluate the changes in WAIS-R-SF scores during follow-up using the general linear mixed models. Model 1 was adjusted with minimally covariates including age, sex, and education year. Model 2 was additionally adjusted for PTABTE, history of disease (hypertension, diabetes, dyslipidemia, ischemic heart disease and stroke), smoking status, marital status, occupation, obesity, depression, and income. The main effect of time on Similarities was not significant in model 1 (p = 0.144), however, it became significant after adjusted various covariates (p = 0.013). In final model, the main effect of time on Picture completion was not significant (p = 0.101 in model 2), although the effects on other scores were significant (Information and DSST, p < .0001 in model 2). The effects of usage of HA on Picture completion and DSST became significant after adjusting for age, sex, education, marital status, occupation, income, depressed mood, smoking status, obesity, and history of disease (hypertension, dyslipidemia, diabetes, ischemic heart disease, and stroke). There was no difference in the Information score at baseline in the HA use group and no HA use group, however, the HA use × time (follow-up years) interaction was significant after adjusting for confounders, and the p-values were 0.033 in model 1 and 0.040 in model 2.

Table 3. Results of general linear mixed model for WAIS-R-SF scores.

Explanatory variables Information Similarities Picture completion Digit symbol substitution (DSST)
Estimate SE p-value Estimate SE p-value Estimate SE p-value Estimate SE p-value
Model 1 Time -0.164 0.034 < .0001 -0.064 0.044 0.144 0.059 0.034 0.079 -0.591 0.075 < .0001
Usage of hearing aid -0.444 0.514 0.388 -0.185 0.490 0.706 0.637 0.379 0.093 0.714 1.032 0.490
Time × usage of hearing aid 0.104 0.048 0.033 -0.019 0.062 0.755 -0.035 0.047 0.457 -0.156 0.110 0.160
Model 2 Time -0.163 0.034 < .0001 -0.061 0.044 0.013 0.059 0.034 0.101 -0.586 0.075 < .0001
Usage of hearing aid -0.066 0.546 0.904 0.471 0.521 0.366 1.616 0.394 < .0001 2.214 1.091 0.043
Time × usage of hearing aid 0.100 0.048 0.040 -0.031 0.062 0.614 -0.040 0.047 0.404 -0.169 0.109 0.122
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Model 1 was adjusted for age, sex, education year.

Model 2 was adjusted for the covariates in model 1 + PTABTE, history of hypertension, history of diabetes, history of dyslipidemia, history of stroke, history of ischemic heart disease, smoking status, marital status, occupation, obesity, depression, and income.

PTABTE: pure-tone average threshold level of the better ear at frequencies of 500, 1000, 2000 and 4000 Hz

The predicted models of the 12-year change in WAIS-R-SF scores with or without HA use are shown in Fig 2. The Information score in HA users declined slower than non-users, although there was no difference in baseline scores. The scores of Similarities declined significantly only in HA users, although there was no significant difference in the rate of change between HA users and non-users. There were no significant changes in Picture completion scores over time in either the HA users or non-users. The DSST scores declined significantly in both HA users and non-users, and there was no significant difference in the rate of change between HA users and non-users.

Fig 2. Model-predicted 12-year change in cognitive ability by hearing aid use in participants with moderate hearing loss.

Fig 2

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A. Result of Information. B. Result of Similarities. C. Result of Picture completion. D. Result of Digit symbol substitution. General linear mixed model adjusted for age, sex, PTABHE, education year, history of hypertension, history of dyslipidemia, history of diabetes, history of ischemic heart disease, history of stroke, smoking status, obesity, marital status, income, depression, and occupation at baseline. PTABTE: pure-tone average threshold level of the better ear at frequencies of 500, 1000, 2000, and 4000 Hz.

The Results of general linear mixed analyses excluded the data of Time 6–8 are shown in S1 Table. The HA x time interaction of the Information score was significant when the analysis was performed excluding Time 8, however, it was no longer significant after excluding Time 8 and 7. The main effect of HA use on the scores of Picture completion and DSST tended to be kept.

Discussion

In this longitudinal study, we found that participants with moderate hearing loss who used HA retained their Information scores, whereas the Information score declined in those who did not use HA. We had previously investigated the effect of hearing loss over 25 dB on the WAIS-R-SF scores in participants aged 60–79 years at baseline [6]. The hearing loss × time interaction was significant for the Information and DSST scores. Studies investigating the effect of age on WAIS scores have demonstrated that Information and Similarities scores have stability during aging [25, 26], although the tolerance of the Information score was lost in hearing-impaired individuals in a previous study [6]. In the present analysis, this decline in the Information score was suppressed in the HA using group. The retention of the Information score may be attributed to the fact that HA use allowed participants to continue acquiring verbal information. In other words, people with moderate hearing loss may be more vulnerable to inadequate information. In contrast, we observed that the decline in the DSST score was significantly steeper in the hearing-impaired group than in hearing participants in our previous study [6], although HA use showed no significant longitudinal association with DSST score changes in this study. The DSST measures processing speed and is considered to be highly reflective of aging. Therefore, DSST was sensitive in revealing the correlation of hearing loss and cognitive function in some cross-sectional studies [27, 28], and Lin reported that HA use was significantly associated with higher DSST scores. However, in longitudinal studies, the association between hearing loss and the DSST score has been controversial [29, 30]. Furthermore, some reports have stated that HA use had no significant effect on changes in the DSST score [31, 32], whereas a recent study reported that HA use improved the DSST score [33]. The DSST is sensitive to the presence of cognitive dysfunction and changes in cognitive function across a wide range of clinical populations, including dementia, depression, schizophrenia, and sleep disorder [34]. The fact that DSST is sensitive to such conditions may explain these controversial results. In contrast to the DSST, scores of Picture completion did not decrease after covariates were adjusted, furthermore, they tended to increase in non-HA users. It has been suggested that the Picture completion might be resilient to the impact of brain damage [35], and be maintained better with age than most other performance tests [20]. Thus, we thought scores of Picture completion did not decrease after adjusting for covariates such as practice effects [36].

We also found that participants with moderate hearing loss who used HA had higher baseline Picture completion and DSST scores than those who did not use HA, although the changes in these scores over time did not significantly differ from those in non-HA users. It is reported that the Information and Similarities subtests are verbal tests reflecting crystalized intelligence that is accumulated through life experiences and education, while Picture completion and DSST subtests are performance tests reflecting fluid intelligence that is sensitive to aging [25]. Fluid intelligence is the ability to solve problems when adapting to new learning and is an important resource for dealing effectively with new experiences [37]. The results of the tests reflecting fluid intelligence were high at baseline, indicating that participants with high fluid intelligence tended to use HA actively.

Some review articles have pointed out three dominant hypotheses underlying the relationship between hearing and cognition: (a) the common cause hypothesis, (b) the cognitive load hypothesis, and (c) the cascade hypothesis [38–40]. The common cause hypothesis suggests that common factors, such as genetic factors, microvascular insufficiency, or oxidative stress cause both hearing loss and cognitive decline. In this model, hearing loss and cognitive function change in parallel, and the causality is unclear. The cognitive load hypothesis postulates that degraded auditory input due to hearing loss places an increased demand for limited processing resources. The cascade hypothesis can be further divided into two hypotheses: one theory states that auditory deprivation causes reallocation of cognitive resources, which leads to cognitive decline, while the second theory suggests that problems such as inactivity, depression, and social isolation caused by hearing loss accelerate cognitive decline. These hypotheses may be intricately involved. The different influences of hearing and HA use on each cognitive domain, such as the results of the four tests of WAIS-R-SF, may reflect this complexity.

The HA usage rate among participants with moderate hearing loss was 31.4% in Japanese community-dwelling older adults aged 60 years or more. The HA using participants were significantly younger and had worse PTABTE, higher education levels, and less depressed mood than the participants who did not use HA. Worse PTABHE and high education have been reported to be important factors for HA use [41] or HA acquisition [42] in the Epidemiology of Hearing Loss Study. Participants with longer education periods had a higher income; moreover, they would manage their health and use the devices more effectively. They may also be more motivated to wear HA. The frequency of participation in the survey was significantly higher among HA users. Hearing loss has been reported to increase the likelihood of clinically relevant depression symptoms in the older adult population, although the effect of HA use on depressed symptoms is controversial [43]. In this study, it was unclear whether participants did not use HA because they had depression, or whether participants who used HA were less likely to get depressed. However, it is presumed that many HA users were motivated because they frequently participated in the study. We previously reported that openness has a protective effect against the decline in Information and Similarities scores [44]. In this analysis, we could not adjust for openness because openness was assessed only in the 2nd and 7th waves. Thus, it is possible that the background of HA users influences this result more than the use of HA itself, although we adjusted for the confounders such as age, sex, education, marital status, occupation, income, depressed mood, smoking status, obesity, and history of disease.

This study had some limitations. Since we set the baseline at the point where moderate hearing loss was detected, the timing of starting HA use was different for each participant. Furthermore, we could not evaluate the HA fitting situation. HA has long been available to the consumer through internet or retail outlets in Japan, without the need of a hearing test to purchase. It was reported that 17.4% of HA owners purchased them through internet or mail order [14], and personal sound amplification products (PSAPs) and HA are sometimes not distinguished. Thus, some participants may treat PSAPs as HA. Second, we analyzed participants aged 60 years or more owing to the small number of participants with moderate hearing loss under the age of 60 years. However, the Lancet Commission on Dementia Prevention, Intervention and Care noted that midlife hearing loss is one of modifying risk factors [4]. Thus, it is necessary to continue to study the effects of HA on middle-aged people with hearing loss. Third, our study sample size was relatively small, and we could not adjust the data with all of the relevant covariates due to missing data. In addition, the significant difference of the Information score’s change was not observed when the follow-up period was limited. However, NILS-LSA is one of the largest studies that evaluates pure-tone audiometry in Japan, and the difference in the impact of HA on each subtest is important for considering the association between hearing and cognition.

Conclusions

We found that participants with moderate hearing loss who used HA for an average period of 4.5 years retained their Information score, whereas the score declined in those who did not use HA in this longitudinal study. The 12-year slopes did not differ between HA users and non-users for the Similarities, Picture Completion and DSST scores. Our study showed that HA use could have a protective effect against the decline in general knowledge in older adults with moderate hearing loss.

Supporting information

S1 Table. Results of general linear mixed model for WAIS-R-SF scores excluding data from Times 6–8; 7–8 and 8.

Adjusted for age, sex, PTABHE, education year, history of hypertension, history of dyslipidemia, history of diabetes, history of ischemic heart disease, history of stroke, smoking status, obesity, marital status, income, depression, and occupation at baseline.

(DOCX)

Click here for additional data file. (18.8KB, docx)

Acknowledgments

We thank all of the participants and our colleagues in the NILS-LSA.

Data Availability

Data cannot be shared publicly because of NILS-LSA's rules. Data are available from the National Center for Geriatrics and Gerontology for researchers who meet the criteria for access to confidential data. HP:https://www.ncgg.go.jp/ri/lab/cgss/department/ep/index.html Address:Department of epidemiology of aging, Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, 7-430 Morioka, Obu, Aichi 474-8511, Japan TEL:81-562-46-2311 FAX:81 -562-44-8518 E-mail:otsuka@ncgg.go.jp.

Funding Statement

This study was supported research grants from the Research Funding of Longevity Sciences from the National Center for Geriatrics and Gerontology (19-10 for RO, 21-18 for RO). https://www.ncgg.go.jp/ncgg-kenkyu/index.html This study was partially supported by research funds from the Japan Agency for Medical Research and Development (19de0107004h0001) for HS. https://research-er.jp/projects/view/1071365. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Decision Letter 0

Masaki Mogi

11 May 2021

PONE-D-21-13516

Longitudinal effects of hearing aid usage on cognition in community-dwelling Japanese older adults with moderate hearing loss.

PLOS ONE

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Reviewer #1: This epidemiologic study focused on the protective effect of hearing aids in older adults. The experiment itself is carried out with careful treatments, but the reviewer thinks the sample size is too small.

Methods

Why were the participants under 60 years old excluded?

Please explain the reason. Usually, the definition of old age is over 65 years old.

Table 1

This table was not informative. Please create a flow-chart.

The number of participants on each group should be shown.

Table 1

The follow-up rates were under 20% from “Time 6”. How were the results changed, if the analysis was performed until “Time5”?

Methods

Were the participants with otological diseases, like otitis media excluded? Please explain it.

Methods

The reviewer thought that the covariates were not enough in this study. The previous report which the authors published on Auris Nasus Larynx included more covariates than this study. Please include more covariates and re-calculate the data. Obesity, history of hyperlipidemia, alcohol intake and history of cardiovascular disease, like stroke and ischemic heart disease are essential covariates, when the cognitive functions are analyzed.

Results

Why were the picture completion scores higher than baseline on both groups? Are the picture completion tests not useful tests on evaluating cognitive function? Please explain it.

Results

Only one model was shown on Table 3. Please create more than two models.

Discussion from 297 to 308

This paragraph should be stated at method section.

Abbreviations about hearing aids were incorrect like “Has” at some points. Please correct them to “HA”.

Reviewer #2: This is a well-conducted study of the association of hearing aid usage with longitudinal cognitive function among 407 older adults with moderate hearing impairment. Given the prevalence of hearing impairment, and prevalence of cognitive decline with age, this is an important and relatively under-studied area. This study represents an important contribution to the literature. Strengths include the relatively large number of participants; objective measures of hearing thresholds; control for many important potentially confounding factors; longitudinal measures, and use of general linear mixed effects regression models. Limitations are adequately noted. However, I have several suggestions for improvement:

Title: Since this is an observational study that describes the association between hearing aid usage and cognitive decline it is important to avoid language the implies causation. Thus the word “Effects” should be changed to “Associations” in the title and throughout the text.

For the full implication of the results to be appreciated from the abstract, it is important to state that slopes did not differ between HA users and non-users for the Similarities, Picture Completion and Digit Symbol Substitution tests.

Line 49 include “is”: The global population of older adults is expected to reach 1.4 billion by 2030 and 2.1 billion by 2050.

Line 88: avoid causal language such as “HAS use influenced changes…” since differences between HA users and non-users may arise from uncontrolled confounding.

In a few places in the manuscript, hearing aid use is sometimes abbreviated as “ha” or “has” – rather than HA or HAs.

It would be helpful if Table 1 was stratified by hearing aid use and non-hearing aid use to allow the reader to appreciate the difference in participation/follow-up time between these two groups.

It would be helpful to report on the average time interval between baseline and report of HA use, as well as the range of that interval. This is important to appreciate how much time may have passed between the onset of hearing impairment and beginning of use of hearing aids, which could affect associations with cognitive function.

Line 312-313. It is unclear why being a local resident would affect whether participants considered PSAPs as HAs. It is not clear whether the authors are implying that participants may have indicated HA use when they were not using HA, but were using PSAPs? "In addition, personal sound amplification products (PSAPs) may be treated as HAs, because the participants were local residents so they may not be able to distinguish HA from PSAPs”.

Conclusion: As with the abstract, it is important to note the implications of the non-significant findings as well. That is, these results shows that HA usage is not associated with reduction in rate of cognitive decline in some tasks that show significantly higher rates of decline among individuals with hearing impairment relative to those without hearing impairment.

*Authors indicate that they are unable to share their data due to third party restrictions.

**********

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Reviewer #2: No

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PLoS One. 2021 Oct 13;16(10):e0258520. doi: 10.1371/journal.pone.0258520.r002

Author response to Decision Letter 0

3 Sep 2021

Our incorporation of the Reviewer comments is as follows:  

 

The changed part in the manuscript was shown in red color.

To reviewer #1: This epidemiologic study focused on the protective effect of hearing aids in older adults. The experiment itself is carried out with careful treatments, but the reviewer thinks the sample size is too small.

→Thank you for reviewing our manuscript. As you pointed out, the sample size was not large. However, NILS-LSA is one of the largest cohort studies in Japan that assessed pure-tone audiometry, and we tried to increase the sample size by collecting and reconstructing the samples with moderate hearing loss from all participants. We mentioned this limitation in discussion. (Line 107-110, 345-350)

Methods

Why were the participants under 60 years old excluded?

Please explain the reason. Usually, the definition of old age is over 65 years old.

→In Japan, people over 60 have been regarded as elderly and retired. Of course, the current situation is that they are being reviewed to make them over 65. Also, the NILS-LSA was designed to have the same number of participants in each decade (40s, 50s, 60s, 70s). Thus, we did not change the definition of old age as over 65 years old in accordance with our previous study.

Table 1

This table was not informative. Please create a flow-chart.

The number of participants on each group should be shown.

→We added a flow-chart (Fig 1). We also added the number of HA users to Table 1 as the reviewer#2 suggested.

Table 1

The follow-up rates were under 20% from “Time 6”. How were the results changed, if the analysis was performed until “Time5”?

→We performed additional analyses excluding Time 6-8, and added these results as S1 Table. (Line 200, 201, 261-264)

Methods

Were the participants with otological diseases, like otitis media excluded? Please explain it.

→We did not exclude the participants who had the history of ontological diseases because there were 50 participants of 407 whose data was missing. We added the explanation and discussed it. (Line 114, 115, 345-350)

Methods

The reviewer thought that the covariates were not enough in this study. The previous report which the authors published on Auris Nasus Larynx included more covariates than this study. Please include more covariates and re-calculate the data. Obesity, history of hyperlipidemia, alcohol intake and history of cardiovascular disease, like stroke and ischemic heart disease are essential covariates, when the cognitive functions are analyzed.

→Choice of covariates is difficult problem. We added obesity, history of hyperlipidemia, and history of ischemic heart disease as suggested. We did not add alcohol intake because there were 48 participants of 407 who lack an answer for the questionnaire about alcohol intake. Again, we discussed this limitation. (Line 345-350)

Results

Why were the picture completion scores higher than baseline on both groups? Are the picture completion tests not useful tests on evaluating cognitive function? Please explain it.

→It has been suggested that the Picture completion might be resilient to the impact of brain damage (Kaufman AS & Lichtenberger EO, Assessing adolescent and adult intelligence. 3rd ed. Hoboken, NJ: John Wiley & Sons, 2006), and to hold up with age better than most other performance tests (Wechsler D. The measurement of adult intelligence. 3rd et. Baltimore, OH: The Williams & Wilkins Company, 1944). Thus, we thought scores of Picture completion did not decrease after adjusting for covariates such as practice effects. We discussed it in previous study (Niahita Y, et al. Does high educational level protect against intellectual decline in older adults? : A 10-year longitudinal study. Jpn Psychol Res 2013;55:378-389). We added the reference and mentioned it. (Line 246, 247, 289-294)

Results

Only one model was shown on Table 3. Please create more than two models.

→We create two models, model 1 is adjusted with covariates same as our previous study (Uchida Y, et al. The longitudinal impact of hearing impairment on cognition differs according to cognitive domain. Front Aging Neurosci 2016;8:201), and model 2 is adjusted with covariates model 1 + depression, income, obesity, and history of dyslipidemia.

Discussion from 297 to 308

This paragraph should be stated at method section.

→We moved this paragraph to method section. (Line 154-165)

Abbreviations about hearing aids were incorrect like “Has” at some points. Please correct them to “HA”.

→We corrected as suggested.

To reviewer #2: This is a well-conducted study of the association of hearing aid usage with longitudinal cognitive function among 407 older adults with moderate hearing impairment. Given the prevalence of hearing impairment, and prevalence of cognitive decline with age, this is an important and relatively under-studied area. This study represents an important contribution to the literature. Strengths include the relatively large number of participants; objective measures of hearing thresholds; control for many important potentially confounding factors; longitudinal measures, and use of general linear mixed effects regression models. Limitations are adequately noted. However, I have several suggestions for improvement:

→We deeply appreciate your kind comments.

Title: Since this is an observational study that describes the association between hearing aid usage and cognitive decline it is important to avoid language the implies causation. Thus the word “Effects” should be changed to “Associations” in the title and throughout the text.

→We changed as suggested.

For the full implication of the results to be appreciated from the abstract, it is important to state that slopes did not differ between HA users and non-users for the Similarities, Picture Completion and Digit Symbol Substitution tests.

→We added a sentence as suggested. (Line 44, 45)

Line 49 include “is”: The global population of older adults is expected to reach 1.4 billion by 2030 and 2.1 billion by 2050.

→We changed as suggested. (Line 51)

Line 88: avoid causal language such as “HAs use influenced changes…” since differences between HA users and non-users may arise from uncontrolled confounding.

→We changed as suggested. (Line 89, 90)

In a few places in the manuscript, hearing aid use is sometimes abbreviated as “ha” or “has” – rather than HA or HAs.

→We corrected as suggested.

It would be helpful if Table 1 was stratified by hearing aid use and non-hearing aid use to allow the reader to appreciate the difference in participation/follow-up time between these two groups.

→We added the number of HA users to Table 1 as suggested.

It would be helpful to report on the average time interval between baseline and report of HA use, as well as the range of that interval. This is important to appreciate how much time may have passed between the onset of hearing impairment and beginning of use of hearing aids, which could affect associations with cognitive function.

→There were 66 participants who had moderate hearing loss and use HA from the first participation, and we could not know when they began to use HA. So, we added the average time interval between baseline and report of HA use in remaining 62 participants. (Line 121-124)

Line 312-313. It is unclear why being a local resident would affect whether participants considered PSAPs as HAs. It is not clear whether the authors are implying that participants may have indicated HA use when they were not using HA, but were using PSAPs? "In addition, personal sound amplification products (PSAPs) may be treated as HAs, because the participants were local residents so they may not be able to distinguish HA from PSAPs”.

→Opposite to the United States, HA has been available to the consumer through Internet or retail outlets, for example, eyeglass shop, in Japan for a long time. Also, pre-purchase hearing evaluation is not necessary to buy HA. So, people sometimes mistake PSAPs as HA in Japan. We added a sentence explaining the above. (Line 337-341)

Conclusion: As with the abstract, it is important to note the implications of the non-significant findings as well. That is, these results shows that HA usage is not associated with reduction in rate of cognitive decline in some tasks that show significantly higher rates of decline among individuals with hearing impairment relative to those without hearing impairment.

→We added a sentence as suggested. (Line 355, 356)

We corrected some errors, and added one recent study (Line 285, 286, Reference number 33).

Attachment

Submitted filename: response to reviewers.docx

Click here for additional data file. (20.6KB, docx)

Decision Letter 1

Masaki Mogi

21 Sep 2021

PONE-D-21-13516R1Longitudinal associations between hearing aid usage and cognition in community-dwelling Japanese older adults with moderate hearing loss.PLOS ONE

Dear Dr. Sugiura,

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Minor revisions are still necessary in the present study. See the Reviewer's comments and respond them appropriately.

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Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: (No Response)

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: No

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The reviewer thinks authors properly responded to the reviewers' comments and precisely revised the manuscript.

Reviewer #2: The authors have been responsive to prior reviewers and have improved the manuscript. I note below a few minor suggestions to improve clarity:

Abstract line 40 : remove “therefore”

Abstract lines 41 – 43: The following sentence is unclear: “The model-predicted 12-year slope

with centralizing age indicated that the Information score showed no significant decline in the participants using HA, although this tolerance was not found in the participants not using HA.” Do the authors mean that non-HA users showed significant decline in Information scores over the 12 year follow-up period whereas HA users did not? Since the slope in the HA group approached significance, I believe a better interpretation would be that the non HA users showed greater decline over time on Information scores than did HA users.

Results, pg 17, line 242 change were to are: “are shown in Fig 2”

Results, pg 18, line 261 change were to are: “are shown in S1 Table. Also, please change the table title to be more informative. Eg. “Results of general linear mixed model for WAIS-R-SF scores excluding data from Times 6-8; 7-8 and 8”

Results Line 246 – 247. This sentence is unclear: “The Picture completion scores did not decrease especially in the non-users, however, there was no significant difference in the rate of change between two groups”. This would be better expressed as “There were no significant changes in Picture completion scores over time in either the HA or non HA users.”

Table 3: I am not sure it is necessary to show the results from model 1 and model 2. There was no a priori reason for assessing differences between these models, although I understand that additional covariates were added in response to review. However, it would be more meaningful to show results of an unadjusted (or minimally adjusted model – including eg. age, sex, education) and the model with all the covariates (fully adjusted model).

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

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Reviewer #1: No

Reviewer #2: No

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PLoS One. 2021 Oct 13;16(10):e0258520. doi: 10.1371/journal.pone.0258520.r004

Author response to Decision Letter 1

26 Sep 2021

Our incorporation of the Reviewer comments is as follows:    

The changed part in the manuscript was shown in red color.

To Reviewer #1:

The reviewer thinks authors properly responded to the reviewers' comments and precisely revised the manuscript.

→Thanks to your kind review, our manuscript is better.

To Reviewer #2:

The authors have been responsive to prior reviewers and have improved the manuscript. I note below a few minor suggestions to improve clarity:

→Thank you for reviewing our manuscript.

Abstract line 40 : remove “therefore”

→We corrected as suggested.

Abstract lines 41 – 43: The following sentence is unclear: “The model-predicted 12-year slope

with centralizing age indicated that the Information score showed no significant decline in the participants using HA, although this tolerance was not found in the participants not using HA.” Do the authors mean that non-HA users showed significant decline in Information scores over the 12 year follow-up period whereas HA users did not? Since the slope in the HA group approached significance, I believe a better interpretation would be that the non HA users showed greater decline over time on Information scores than did HA users.

→We corrected as suggested.

Results, pg 17, line 242 change were to are: “are shown in Fig 2”

→We corrected the sentence as suggested.

Results, pg 18, line 261 change were to are: “are shown in S1 Table. Also, please change the table title to be more informative. Eg. “Results of general linear mixed model for WAIS-R-SF scores excluding data from Times 6-8; 7-8 and 8”

→We corrected the sentence and changed the title as suggested.

Results Line 246 – 247. This sentence is unclear: “The Picture completion scores did not decrease especially in the non-users, however, there was no significant difference in the rate of change between two groups”. This would be better expressed as “There were no significant changes in Picture completion scores over time in either the HA or non HA users.”

→We corrected the sentence as suggested.

Table 3: I am not sure it is necessary to show the results from model 1 and model 2. There was no a priori reason for assessing differences between these models, although I understand that additional covariates were added in response to review. However, it would be more meaningful to show results of an unadjusted (or minimally adjusted model – including eg. age, sex, education) and the model with all the covariates (fully adjusted model).

→We changed the model 1 as minimally adjusted model. The sentences of results (Line 221-231) were also changed.

Attachment

Submitted filename: response to reviewers0926.docx

Click here for additional data file. (16.7KB, docx)

Decision Letter 2

Masaki Mogi

30 Sep 2021

Longitudinal associations between hearing aid usage and cognition in community-dwelling Japanese older adults with moderate hearing loss.

PONE-D-21-13516R2

Dear Dr. Sugiura,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Masaki Mogi

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

No further comment.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: (No Response)

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: (No Response)

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: (No Response)

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: (No Response)

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: (No Response)

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No

Acceptance letter

Masaki Mogi

4 Oct 2021

PONE-D-21-13516R2

 Longitudinal associations between hearing aid usage and cognition in community-dwelling Japanese older adults with moderate hearing loss.

Dear Dr. Sugiura:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Masaki Mogi

Academic Editor

PLOS ONE

Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    S1 Table. Results of general linear mixed model for WAIS-R-SF scores excluding data from Times 6–8; 7–8 and 8.

    Adjusted for age, sex, PTABHE, education year, history of hypertension, history of dyslipidemia, history of diabetes, history of ischemic heart disease, history of stroke, smoking status, obesity, marital status, income, depression, and occupation at baseline.

    (DOCX)

    Click here for additional data file. (18.8KB, docx)
    Attachment

    Submitted filename: response to reviewers.docx

    Click here for additional data file. (20.6KB, docx)
    Attachment

    Submitted filename: response to reviewers0926.docx

    Click here for additional data file. (16.7KB, docx)

    Data Availability Statement

    Data cannot be shared publicly because of NILS-LSA's rules. Data are available from the National Center for Geriatrics and Gerontology for researchers who meet the criteria for access to confidential data. HP:https://www.ncgg.go.jp/ri/lab/cgss/department/ep/index.html Address:Department of epidemiology of aging, Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, 7-430 Morioka, Obu, Aichi 474-8511, Japan TEL:81-562-46-2311 FAX:81 -562-44-8518 E-mail:otsuka@ncgg.go.jp.

    Articles from PLoS ONE are provided here courtesy of PLOS

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