Obstructive Sleep Apnea Linked to Increased Risk for Dementia, Particularly in Women

Among a cohort of more than 18 000 US adults aged 50 years and older and free of dementia at baseline, a new longitudinal study found that known or suspected obstructive sleep apnea (OSA) was associated with a higher cumulative incidence (CI) of dementia across mid-to-later life and that the CI was more pronounced among women. The findings, authors said, suggest that differences in CI of dementia by OSA status may be both age- and sex-dependent.

Results of the study, from researchers at Michigan Medicine, showed that at all age levels examined, women with known/suspected OSA were more likely than men to be diagnosed with dementia. Moreover, as age increased the increase in the difference in cumulative incidence of dementia among those with known/suspected dementia grew larger for women but stabilized for men. By age 80, the cumulative incidence of dementia among study participants with OSA was 4.7% higher for women (95% CI 2.8%-6.7%) and 2.5% higher for men (95% CI 0.5%-4.5%) compared with adults without the condition.

Findings from the study were published in SLEEP Advances.

“Our findings offer new evidence of a sleep-based pathway that underlies sex-specific differences in dementia risk,” corresponding author Tiffany J Braley, MD, MS, the Holtom-Garrett Family Professor of Neurology, and section head for multiple sclerosis at Michigan Medicine, and colleagues wrote. “Further, as OSA is a treatable condition, this study illuminates the impact of a potentially modifiable yet frequently overlooked risk factor” affecting long-term cognitive health at the population level for both women and men, authors added.

Braley et al tapped data (2010 to 2020) from the longitudinal Health and Retirement Study (HRS) cohort that captures various aspects of health and well-being in a nationally representative sample of Americans aged 50 and older. From an initial sample of 28 058, the team identified adults with known/suspected OSA via self-report or positive results on the validated OSA screening STOP-Bang questionnaire, a tool known to capture undiagnosed cases of OSA. Participants with incident dementia were identified either by self-report, using an HRS-based algorithm based on objective cognitive function assessments. Respondent-level sampling weights were incorporated to ensure results were representative of US community-dwelling adults over age 50 in 2016.

The final sample for analysis comprised 89 155 observations from 18 815 respondents, more than 80% of which were younger than age 70 years, according to the study. Just more than half (54%) were women and the mean age at first cognitive assessment was 61 years.

Approximately half the cohort (48%) met study criteria for known/suspected OSA and investigators reported that prevalence was more than twice as high among men (68%) vs women (31%). They identified 2233 incident cases of dementia, comprising 9% of women and 8% of men in the cohort.

"As OSA is a treatable condition, this study illuminates the impact of a potentially modifiable yet frequently overlooked risk factor affecting long-term cognitive health at the population level for both women and men."

To analyze differences in cumulative incidence of dementia by OSA status the researchers used survey-weighted regression models based on pseudovalues to stand in for covariates including race and ethnicity and education and cohabitation status.

Braley and colleagues, using age 80 years as an example, estimated the fraction of dementia cases due to OSA, or the population attributable risk percent (PAR%), as 10.3% for women and 13.2% for men, the lower rate among women explained potentially by the overall lower prevalence of OSA in the cohort among women (31%) vs men (68%), as mentioned.

In models adjusted for race and ethnicity and education and cohabitation status, the researchers reported attenuated impact of known/suspected OSA on age-specific dementia. The association did remain statistically significant, however, according to the study.

Among the study’s limitations Braley et al note that the STOP-Ban questionnaire is a screening, not a diagnostic tool, and that HRS cognitive scores, while reliable for estimating cognitive function, are not confirmed through neuropsychological testing. In addition, OSA treatment adherence was unknown and could influence cognitive outcomes. Finally, missing data, a common issue in longitudinal research, was addressed with imputation methods.

Nonetheless, Braley and colleagues concluded that the study contributes to the still nascent but growing understanding of the many risk factors, modifiable and otherwise, that contribute to the development of dementia. “We demonstrated a sex-specific association between known or suspected OSA and a decade-long cumulative incidence of dementia,” said the team in its conclusion. “Further research is warranted to examine the role of OSA therapy and potential mediators that lie in the pathways between OSA and dementia, including genetic mutations and comorbidities. Identification of potential mediators could support sex-specific interventions to reduce the incidence of dementia in older women and men with OSA.”

References
1. Braley TJ, Lyu X, Dunietz GL, et al. Sex-specific dementia risk in known or suspected obstructive sleep apnea: A 10-year longitudinal population-based study. Sleep Adv. 2024. doi:10.1093/sleepadvances/zpae077
2. Sleep apnea contributes to dementia in older adults, especially women. News release. Michigan Medicine. October 29, 2024. Accessed November 12, 2024. https://www.michiganmedicine.org/health-lab/sleep-apnea-contributes-dementia-older-adults-especially-women