Association between Sarcopenia, Its Defining Indices, and Driving Cessation in Older Adults

Abstract

Objectives

Driving a car is essential for older adults to support their activities of daily living and maintain their quality of life. However, physical function — which often declines with age — is a key factor to determine whether older adults can continue driving safely. As such, we sought to examine the association between sarcopenia and driving cessation in older adults.

Design

A prospective study.

Setting

A community setting.

Participants

We conducted a study including 2,874 older adult participants from the community (mean age: 71.0 ± 4.7 years [range: 65–93 years], women: 36.3%).

Measurements

We assessed whether they were still driving at baseline examination as well as their degree of sarcopenia. Sarcopenia was assessed according to the clinical definition provided by the EWGSOP2 by measuring muscle mass, muscle strength, and physical performance represented by gait speed. Driving cessation was determined based on driving status at the initial visit and at a follow-up examination approximately 15 months later.

Results

At the baseline assessment, there were 62 participants (2.2%) with confirmed sarcopenia and 23 participants (0.8%) with severe sarcopenia. Participants were classified into either the ongoing driving (n = 2816) or driving cessation (n = 58) group. Low muscle strength and low muscle mass were associated with driving cessation (low muscle strength: odds ratio [OR] 2.09, 95% confidence interval [CI] 1.13–3.87; low muscle mass: OR 2.00, 95% CI 1.04–3.85). Slow gait was not associated with driving cessation (OR 1.35, 95% CI 0.68–2.69). Significantly, sarcopenia was associated with driving cessation (confirmed sarcopenia: OR 4.48, 95% CI 1.63–12.29; severe sarcopenia: OR 4.46, 95% CI 1.21–16.41).

Conclusions

Sarcopenia is associated with an increased likelihood of driving cessation in community-dwelling older adults. Evaluation of physical function related to sarcopenia would be useful for judgment of the ability to drive safely among older adults.

Introduction

Driving a car is essential for many older adults to support their daily activities and to maintain their life-space (1, 2). Driving contributes to promoting a healthy lifestyle among older adults (3); significantly, driving cessation is associated with a decreased quality of life (QOL) (4), and an increased risk of incidents causing disability (5, 6) and dementia (7). Among older drivers, continued safe driving is a useful tool for extending a healthy life expectancy. As such, appropriate risk screening and assessment of older adults is needed to extend their ability to drive safely and to effectively identify when driving cessation is appropriate.

Decreased physical function has been associated with an increased likelihood of driving cessation. Lower physical performances as determined by the Short Physical Performance Battery (SPPB) was associated in one study with disability in walking and driving (8). Furthermore, in an investigation of the association of sensory motor function and driving, only grip strength was found to have a modest association with driving cessation (9). On the contrary, some studies have claimed that physical performances is not associated with driving cessation (10).

Sarcopenia is widely recognized as a major geriatric syndrome and is characterized by progressive and generalized loss of skeletal muscle mass and strength. Sarcopenia is associated with an increased risk of adverse events such as physical disability, poor quality of life and death (11). Accordingly, sarcopenia is a critical factor in the physical health of older adults. However, the association between sarcopenia and driving cessation is not yet understood; thus, this study aimed to elucidate and examine this association.

Methods

Participants

The participants in this study were those included in the population-based Obu Study of Health Promotion for the Elderly (OSHPE) (12), which was part of the National Center for Geriatrics and Gerontology Study of Geriatric Syndromes (13) that aimed to establish a screening program for geriatric syndromes and validate evidence-based interventions for their prevention. An initial survey was conducted in 2011–2012 and the detailed recruiting protocol is described elsewhere (13). Older adults who lived in Obu city and aged 65 or over were requited. A total of 5,104 individuals participated in the initial examination. We conducted a follow-up postal survey approximately 15 months after the baseline assessment, in 2012–2013. We included participants who were driving at the initial examination and excluded participants who did not respond in a follow-up postal survey. In addition, we excluded participants who had missing data for the variables used in this study. A total of 2,874 participants were ultimately analyzed. The investigation was conformed with the principles outlined in the Declaration of Helsinki. All participants provided written informed consent, and the ethics committee of the National Center for Geriatrics and Gerontology approved this study.

Sarcopenia

Sarcopenia was evaluated according to the revised recommendations of the EWGSOP (EWGSOP2) (14). We assessed sarcopenia indices including muscle mass, muscle strength, and physical performance. According to EWGSOP2, confirmed sarcopenia was defined as low muscle mass and muscle strength, whereas severe sarcopenia had low muscle mass and strength, and low physical performance.

To determine muscle mass, the appendicular skeletal muscle mass (ASM) was evaluated by measuring multi-frequency bioelectrical impedance analysis (MC-980A; TANITA, Tokyo, Japan). The ASM was calculated according to a previous study (15) and converted to the skeletal muscle mass index (SMI) by dividing the muscle mass by the participant's height in meters squared (kg/m²). Low muscle mass was defined as an SMI value < 7.0 kg/m² for men and < 5.7 kg/m² for women (16).

Muscle strength was assessed using a handgrip strength test. Handgrip strength was measured using a Smedley-type handheld dynamometer (Takei Ltd., Niigata, Japan). Low muscle strength was defined as handgrip strength of < 26 kg for men and < 18 kg for women (16). To assess physical performance, we measured participants' walking speeds under normal condition. Walking time was measured over 2.4 m in the middle of a straight walkway that was 6.4 m long; walking time was measured between 2.0 m and 4.4 m, as measured from the start of the walkway. Low physical performance was defined as a walking speed of < 1.0 m/s for both men and women (12). Based on the results of these three indices, participants were classified as having no sarcopenia (robust), confirmed sarcopenia, or severe sarcopenia severe (14).

Driving status determination

Participants were asked about their driving status at the initial and 15-month follow-up surveys. Participants were asked to respond “yes” or “no” to the question “Do you drive a motor vehicle?” (9). Driver status was determined based on the answer to this question. Participants who were driving at the initial survey but were no longer driving at the follow-up survey were classified as “ceased driving.”

Other variables

To examine the characteristics of participants who had ceased driving and the potential related factors, demographical and medical data were acquired for participants. Demographic data, age, sex, and educational history were determined by an interview with the participant. Medical data including number of current medications, fall history and cognitive function were also assessed. To evaluate cognitive function, the MiniMental State Examination (MMSE) was used (17). In addition, information regarding whether participants went outdoors was also collected to be thought as a potential effect modifier. Participants with “less frequent outings” were identified if they responded “yes” to the following question from the Kihon Checklist (18): “Do you go out less frequently compared to last year?” The Kihon Checklist was a questionnaire to assess comprehensively geriatric syndromes (18).

Statistical Analysis

Participants were classified into two groups — driving or ceased driving — based on their driving status at the follow-up examination. To compare the characteristics of participants who had or had not ceased driving, unpaired t-tests or χ² tests were used as appropriate. To test the association between degree of sarcopenia and driving status, a logistic regression analysis was used. The objective variable was whether a participant had or had not ceased driving. The degree of sarcopenia (robust, confirmed sarcopenia, severe sarcopenia) was set as the explanatory variable. A logistic regression analysis was conducted using an unadjusted model and an adjusted model with additional potential confounding variables that had difference between groups at baseline. A logistic regression analysis was also used to test the association between individual sarcopenia indices (muscle mass, muscle strength, slow gait speed) and driving cessation. Each index was used as an explanatory variable in an independent logistic regression analysis. The odds ratio (OR) and 95% confidence intervals (CI) were calculated for each model. All analyses were performed using SPSS Version 26 (IBM Corp., Chicago, IL, USA). Statistical significance was defined as p < 0.05 in all analyses.

Results

Participants were classified into two groups: driving (n = 2816) and ceased driving (n = 58), according to their responses to the follow-up examination. The comparison of characteristics between the groups is summarized in Table 1. Compared to participants who were still driving, participants who had ceased driving were older, taking more medications and had a lower MMSE score on average. Furthermore, a greater proportion of participants who had ceased driving reported less frequent outings and had confirmed or severe sarcopenia (all p < 0.01) compared to the driving group. With regards to the sarcopenia indices, on average, the ceased driving group had significantly slower gait speed (driving: 1.23 ± 0.20 m/s, ceased driving: 1.13 ± 0.24 m/s, p < 0.001) and lower grip strength (driving: 29.4 ± 7.7 kg, ceased driving: 26.1 ± 6.7 kg, p = 0.001). However, the average SMI was not significantly different between groups (driving: 7.28 ± 0.93 kg/m², ceased driving: 7.10 ± 1.11 kg/m², p = 0.144).

Table 1.

Baseline characteristics of participants grouped by driving status at follow-up

Variables	Drivinga (n = 2816)	Ceased drivinga (n = 58)	P
Age, years	70.9 (4.7)	73.8 (5.6)	< 0.001
Sex (% Women)	36.2	41.4	0.412
Number of medications	1.9 (2.1)	3.0 (2.8)	< 0.001
Educational history, years	11.8 (2.6)	11.7 (2.2)	0.765
Mini-Mental State Examination, score	26.5 (2.5)	25.4 (3.5)	0.001
Low outing frequency, %	9.6	24.1	< 0.001
Fall history, %	13.3	20.7	0.103
Living alone, %	7.6	8.6	0.736
Sarcopenia
No sarcopenia (robust), %	97.3	86.2	< 0.001
Confirmed sarcopenia, %	2.0	8.6
Severe sarcopenia, %	0.7	5.2

a. Values are mean (standard deviations) or proportions.

The results of a logistic analysis to examine the association between sarcopenia and driving cessation are summarized in Table 2. Both confirmed and severe sarcopenia were found to be associated with driving cessation (confirmed sarcopenia: OR 4.48, 95% CI 1.63–12.29; severe sarcopenia: OR 4.46, 95% CI 1.21–16.41). The association between sarcopenia indices and driving cessation is shown in Fig. 1. In the adjusted model, slow gait was not associated with driving cessation (OR 1.35, 95% CI 0.68–2.69), though low muscle strength and low muscle mass were significantly associated with driving cessation (low muscle strength: OR 2.09, 95% CI 1.13–3.87; low muscle mass: OR 2.00, 95% CI 1.04–3.85).

Table 2.

Correlation between sarcopenia status, other variables and driving cessation

Variables	Unadjusted OR	(95% CI)	p	Adjusted OR	(95% CI)	p
No sarcopenia (robust)	Reference			Reference
Confirmed sarcopenia	4.81	(1.85–12.50)	0.001	4.48	(1.63–12.29)	0.004
Severe sarcopenia	8.22	(2.37–28.55)	0.001	4.46	(1.21–16.41)	0.024
Age				1.09	(1.03–1.15)	0.001
Sex (ref: women)				0.49	(0.27–0.87)	0.015
Number of medications				1.14	(1.03–1.26)	0.011
Educational history				1.07	(0.96–1.19)	0.202
Mini-Mental State Examination				0.86	(0.78–0.95)	0.002
Low outing frequency				2.07	(1.08–3.96)	0.029
Fall history				1.33	(0.68–2.60)	0.402
Living alone				1.29	(0.49–3.39)	0.608

OR: odds ratio; CI: confidence interval.

Figure 1.

Odds ratios of sarcopenia indices for driving cessation

Odds ratios was adjusted for age, sex, number of medications, educational history, Mini-Mental State Examination score, frequency of outings, fall history, and whether the individual lives alone

Discussion

Our study revealed that there is an association between sarcopenia and driving cessation. Participants who had ceased driving typically were older, took more medications, had lower cognitive function and went for less frequent outings than those who were still driving. After adjusting for participant characteristics, the association between sarcopenia and driving cessation persisted. Furthermore, low muscle mass and low muscle strength were associated with driving cessation, though a slow gait speed was not significantly associated with driving cessation.

Originally, sarcopenia was defined only by low muscle mass (19); however, consensus groups recommended the assessment of physical performance to identify sarcopenia (14, 20). Now, both low muscle mass and low muscle strength are required to determine that an individual has sarcopenia in accordance with EWGSOP2 (14). In our study, both low muscle mass and low muscle strength were found to be associated with driving cessation. Grip strength has been identified in previous studies as a factor associated with driving cessation (9). Furthermore, frailty — which includes low muscle strength as a criteria — has been shown to predict driving cessation (21). A US longitudinal cohort study recruited 2,990 older adult drivers and showed that frailty was positively associated with low-mileage driving status and driving cessation in a dose-response fashion (22). In addition, sarcopenia interacts with other geriatric syndromes and has been shown to be a key factor in accelerating the negative cycle of frailty (23). Thus, driving cessation may occur in the progression of sarcopenia to disability. Our study is consistent with, and has expanded upon, the results of previous investigations.

Our study revealed that low functioning in the lower extremities did not reinforce the association between sarcopenia and driving cessation. Low physical performance and extremity functioning performance determined by the SPPB has been associated with driving cessation (24, 25). However, another cohort study with a longer follow-up duration (10 years) revealed that vision function was a predictive factor for driving cessation, whereas walking time was not (10). This discrepancy may arise in part from the measurements used to evaluate physical performances. For example, the SPPB assesses walking speed, balance and the ability to rise from chair and is an effective performance measure to comprehensively evaluate lower extremity functioning (26), while gait speed can be used to directly assess mobility. Thus, in screening for likelihood of driving cessation, a multi-faced evaluation of mobility is most appropriate. In addition, the associations between physical performance and driving outcomes may depend on the specific driving outcome being examined. For example, the association of physical performance and driving outcomes related to motor vehicle collisions is unclear, but physical function including grip strength and walking speed are not significantly associated with car accidents (27, 28, 29). As such, it is important to consider both the potential relevant factors and the driving outcome of interest to screen drivers appropriately.

While our study was designed prospectively and had a large sample size, making it more robust, there are still limitations to this study. Firstly, driving cessation was defined based on the results of follow-up examination. Thus, the exact timing of driving cessation was not collected promptly. Additionally, the medical conditions and the ability to drive in a promptly timing manner should also be studied in future studies. In addition, the interval between initial and follow-up examination was relatively short; thus, a prospective study with a longer follow-up period is also required to further validate these conclusions. Increasing the period between the initial baseline and the follow-up examination in future prospective studies would be useful to validate the generalizability of the study findings.

In conclusion, we found that sarcopenia was associated with driving cessation in community-dwelling older adults. Thus, physical function evaluation is needed for safe renewal of driver's licenses in older adults.

Conflict of Interest Disclosures

None of the authors have any financial, personal, or potential conflict of interest with the material presented in this article.

Funding

This work was supported by a Health Labour Sciences Research Grant (H23-tyoujyu-ippan-001), a Grant-in-Aid for Scientific Research (B) (grant number 23300205), and Research Funding for Longevity Sciences (22-16, 30–7) from the National Center for Geriatrics and Gerontology, Japan.

Ethical standards

Ethical standards for epidemiological study were adhered to according to guidelines from the Ministry of Health, Labour and Welfare, Japan.