Abstract
Background:
The association between obstructive sleep apnea (OSA) and cognitive decline among older adults is a still a topic of debate. Objective: The aim of this study was to determine the association between risk of OSA and cognitive function among Saudi older adults.
Methods:
This was a cross-sectional community-based study conducted between July and October 2022. Participants were recruited from gathering areas where older adults are likely attending such as district centers, waiting areas of shopping malls, and mosques. Questionnaires were completed using face-to-face interviews. The questionnaire included questions of sociodemographics, sleep pattern and health status. A validated Arabic version of Athens insomnia scale, STOP-BANG questionnaire, and St. Louis University mental status (SLUMS) questionnaire were used. A multi-Linear regression model was used to determine the association between cognitive functions and OSA.
Results:
A total of 343 participants were recruited in this study, of which 86% were male. The mean age was 65±9 years. 65% of participants with high risk of sleep apnea were diagnosed with either dementia or mild cognitive impairment (MCI). Most of the participants who were illiterate (83%) had dementia, while only 4% of participants with higher education had dementia.
Conclusion:
Dementia and mild cognitive impairment is prevalent among Saudi older adults with high risk of OSA. Clinicians and patients should be aware of the risk of developing dementia in patients with OSA, especially if remain untreated.
Keywords: Nap, cognitive function, elderly, sleep, geriatrics
1. BACKGROUND
Obstructive sleep apnea (OSA) is one of the highly prevalent sleep-related breathing disorders that affect 40%-60% of older adults, yet it is often undiagnosed (1). OSA is a condition known to have serious consequences that impact patients’ quality of life. Multiple studies showed that OSA is associated with cardiovascular diseases, diabetes mellites, hypertension, stroke, depression, and cognitive decline (1-3).
Recent studies have shown an association between age and cognitive deterioration in patients with OSA. A meta-analysis of 42 studies has concluded that compared to the healthy controls, verbal and visuospatial episodic memories are impaired in patients with OSA (4). Another prospective study of 298 healthy women found that older OSA women are at a greater risk to develop cognitive decline after 5 years from the occurrence of OSA (5). However, other studies showed no impact of OSA on cognitive function (6, 7).
Despite the potential association between OSA and major cognitive decline, there are scarce evidences that support such association, particularly, in Saudi Arabia. Thus, this study aimed to determine the association between cognitive function and risk of OSA among Saudi older adults. We hypothesized that there will be an association between cognitive decline and risk of OSA in such a population.
2. OBJECTIVE
The aim of our study was to determine the association between risk of OSA and cognitive function among Saudi older adults.
3. MATERIAL AND METHODS
Participants
Full details of this study were explained elsewhere (8). In brief, this was a cross-sectional community-based study conducted between July and October 2022. Participants were recruited from areas where the geriatric population will attend such as visitors of a teaching hospital, shopping malls, mosques and vaccine centers in Saudi Arabia. Inclusion criteria were individuals of 60 years or older. Participants were excluded from the study if they report recent head trauma in the past 3 months. All participants gave written informed consent, and the study was approved by the Institutional Review Board of Imam Abdulrahman bin Faisal university (IAU) (IRB Number -2022-01-136).
Measurements
Questionnaires were completed using face-to-face interviews by either a physician or a family medicine trainee. The family medicine trainees were trained by geriatricians in how to conduct the interview. The questionnaire collected data of the participants’ sociodemographic, sleep pattern and health status. A validated Arabic version of Athens insomnia scale, STOP-BANG questionnaire, and St. Louis University mental status (SLUMS) examination were used (9).
Athens Insomnia Scale
This scale measures the intensity of sleep difficulties. It is an 8-item questionnaire that pertains to sleep induction, early awakening and awakening during the night, total sleep duration, sleep quality and daytime wellbeing, functioning capacity and sleepiness. A cut-off score of ≥ 6 points was used to detect insomnia (10).
Stop-Bang
A questionnaire consists of eight dichotomous (yes/no) items related to clinical features of obstructive sleep apnea (OSA). The total score ranges from 0 to 8. Patients were categorized either as a low risk for presence of OSA if they score between 0 to 2 and as high risk if they score between 3 to 8 (11).
The St. Louis University Mental Status Examination
The SLUMS is a 30-point, 11-item scale that is used to identify people with dementia or mild neurocognitive impairment. The total possible score is 30. Interpretation of the score depends on the level of education; High school education: Normal: 27–30; Mild neurocognitive disorder: 21–26; Dementia: 1–20. Less than high school education: Normal: 25–30; Mild neurocognitive disorder: 20–24; Dementia: 1–19. We used the validated Arabic version of the SLUMS in our study (9).
Statistical Analysis
Mean and standard deviation were used for continuous variables, and count and percentage were used for categorical variables. Kruskal–Wallis test was used for skewed variables, and chi-square test for categorical variables. ANOVA was used to test for differences across napping duration for normally distributed continuous variables
We used multivariable linear regression to study the association between OSA and risk of developing cognitive impairment adjusting for known confounders including age, sex, education level, sleep hours, diabetes mellitus (DM), hypertension (HTN), pain, risk of insomnia and risk of sleep apnea. All statistical tests were two-sided, using p-value of 0.05 for statistical significance. Analyses were performed using (R version 4.1.1).
4. RESULTS
The total sample is composed of 343 participants from the elderly community (above 60 years old). The average age was 65±9 years and majority of them were males (n= 233, 68%). The results showed that there was no association between insomnia and MCI nor dementia. Table 1 below shows the baseline characteristics and variables associated with dementia using SLUMS scale.
Table 1. Variables association with dementia using SLUMS scale.
| Variable | Category | Total Frequency (%) | Dementia Assessment SLUMS categories | Test (P-value) | ||
|---|---|---|---|---|---|---|
| Normal (n=113) | Mild cognitive impairment (n=123) | Dementia (n=107) | ||||
| Age | Median (IQR) | 65 (9) | 64 (6) | 65.0 (7) | 66 (12) | Kruskal Wallis H= 9.92 (.007) |
| Gender | Male | 233 (67.9) | 85 (75.2) | 87 (70.7) | 61 (57.0) | x2= 9.06 (.011) |
| Female | 110 (32.1) | 28 (24.8) | 36 (29.3) | 46 (43.0) | ||
| Education | Illiterate | 51 (14.9) | 4 (3.5) | 4 (3.3) | 43 (40.2) | x2= 122.63 (<.001) |
| Primary school | 46 (13.4) | 11 (9.7) | 14 (11.4) | 21 (19.6) | ||
| Elementary school | 45 (13.1) | 8 (7.1) | 25 (20.3) | 12 (11.2) | ||
| high school | 74 (21.6) | 22 (19.5) | 31 (25.2) | 21 (19.6) | ||
| university | 100 (29.2) | 50 (44.2) | 41 (33.3) | 9 (8.4) | ||
| higher education | 27 (7.9) | 18 (15.9) | 8 (6.5) | 1 (0.9) | ||
| Living area | City | 327 (95.3) | 109 (96.5) | 119 (96.7) | 99 (92.5) | x2= 2.78 (.250) |
| Village/rural | 16 (4.7) | 4 (3.5) | 4 (3.3) | 8 (7.5) | ||
| Take pills for chronic pain | No | 248 (72.3) | 88 (77.9) | 86 (69.9) | 74 (69.2) | x2= 2.63 (.268) |
| Yes | 95 (27.7) | 25 (22.1) | 37 (30.1) | 33 (30.8) | ||
| Take sleep pills | No | 320 (93.3) | 105 (92.9) | 116 (94.3) | 99 (92.5) | x2= .33 (.848) |
| Yes | 23 (6.7) | 8 (7.1) | 7 (5.7) | 8 (7.5) | ||
| Athens category | No Insomnia | 259 (75.5) | 90 (79.6) | 92 (74.8) | 77 (72.0) | x2= 1.81 (.405) |
| Insomnia | 84 (24.5) | 23 (20.4) | 31 (25.2) | 30 (28.0) | ||
| Stop Bang Category | Low risk (0 – 2) | 84 (24.5) | 23 (20.4) | 25 (20.3) | 36 (33.6) | x2= 7.05 (.029) |
| High risk (3 – 8) | 259 (75.5) | 90 (79.6) | 98 (79.7) | 71 (66.4) | ||
| Bold indicates statistical significance | ||||||
OSA and Cognition
Seventy-five percents of our sample were at higher risk of having OSA. When assessing the association between sleep apnea and dementia, the results showed that 65% of participants with high risk of sleep apnea were diagnosed with either dementia or mild cognitive impairment and this association was statistically significant (P=0.029).
Cognition and Other Parameters
Several of the assessed variables were found to be significantly related to dementia. Figure 1 shows the distribution of participants in each cognitive decline domains; majority were fall in the dementia category. Although females were less than males in the study sample, but the results show that 42% of females have dementia (n= 46 of 110 females in the study), while only 26% of males do (n= 61 of 233 males in the study), this difference is statistically significant (x2= 9.058, P= .011).
Figure 1. The association between age and dementia.
Furthermore, education seems to play a significant role on dementia (x2= 122.633, P <.001). Most of the participants who were illiterate had dementia (n= 43, 83% of all illiterate participants in the study), while only 4% of participants with higher education had dementia. The results showed that education is a protective factor from dementia, the lower the education, the higher is the risk of dementia (Figure 2).
Figure 2. Variables that are significantly related to dementia.
The rest of the variables in the study did not show any significant association with dementia; These variables were living area (x2= 2.776, P= .250), taking pills for chronic pains (x2= 2.630, P= .268), taking sleeping pills (x2= .329, P= .848), and insomnia (x2= 1.807, P= .405).
5. DISCUSSION
The primary finding of this study was that there was a significant association between risk of OSA and dementia or mild cognitive impairment. Up to our knowledge, this was the first study to assess OSA association with dementia among geriatric population in Saudi Arabia.
Our results showed that 66.4% of participants with dementia had high risk of OSA and 79.7% of participants with mild cognitive impairment had high risk of OSA. This finding is in agreement with previous studies that showed OSA patients were at a 1.7-1.85 increased risk of dementia or mild cognitive impairment. Yaffe et al (2011) studied around 300 older women with a 5-year follow up and reported that OSA was a risk factor for the cognitive impairment. They also showed that treating OSA may slow or even improve cognitive impairment, yet this was not studied in our present study (12). Chang et al (2013) Studied a data-based population sample with more than 1400 patients newly diagnosed with OSA. After a follow up for 5 years, they reported increased risk of dementia or mild cognitive impairment in patients with OSA (5, 13). It has been proposed that repeated apneic episodes during sleep results in intermittent hypoxemia, hypercapnia, sympathetic activation of nervous system, arousal from sleep, and sleep fragmentation; all of which contribute to major neurological disorders and early onset of cognitive impairment (3, 14, 15). Because OSA is often diagnosed late in one’s life, it could be that the cognitive impairment due to OSA may have been detected earlier. Previous studies suggested that neuropsychiatric traits may occur at younger age and early in the disease onset but become more pronounced with disease advancement (16).
It is known that men are 2 – 3 times more likely to be diagnosed with sleep apnea than women, and the incidence in both sexes increases dramatically with age. This suggests that sex hormones play a role in the development of sleep apnea. Estimates of the prevalence of sleep apnea indicate sex differences occur worldwide (17). On the other hand, OSA was significantly associated with cognitive impairment and frailty elderly females more than elderly males (18, 19).
This study has several limitations. First, OSA was assessed using STOPBANG questionnaire and there was no confirmatory sleep study. However, STOPBANG questionnaire is a validated tool for assessing the risk of OSA, and previous studies indicated that STOPBANG questionnaire has an excellent sensitivity and specificity of in predicting moderate to severe OSA (20, 21). Second, the cognitive decline was assessed using SLUMS, which is a global measure of cognitive decline. It could be, however, that specific domains of cognitive function deteriorate more than other areas (22). These warrants further investigation. One of the strengths of this study was that up to our knowledge, this was the first study to assess OSA association with dementia among geriatric population in Saudi Arabia. Another strength of this study was that variety of data collection cites which reflects true representation of general population in Saudi Arabia.
6. CONCLUSION
The main finding of this study was that dementia and mild cognitive impairment is prevalent among Saudi older adults with high risk of OSA. Clinicians and patients should be aware of the risk of developing dementia in patients with OSA, especially if OSA remains untreated.
Author’s contribution:
All authors were involved in all steps of preparation this article. Final proofreading was made by the first author.
Conflict of interest:
None declared.
Financial support and sponsorship:
Nil.
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