Sleep apnea increases dementia risk in older women

New study finds that obstructive sleep apnea may increase the risk of dementia, with older women most vulnerable, highlighting the need for targeted interventions in sleep health and cognitive care.

Study: Risk of dementia by gender in known or suspected obstructive sleep apnea: A 10-year longitudinal population-based study. Image credit: Andrey Popov / Shutterstock.com

A new study published in SLEEP proceeds identifies the differential risk of dementia between men and women based on the presence of obstructive sleep apnea (OSA).

Dementia threat in the US

Dementia refers to a progressive and incurable decline in cognitive function often accompanied by behavioral changes due to neurodegenerative disease. Current estimates indicate that seven million Americans have been diagnosed with dementia. Therefore, it is important to identify modifiable risk factors for targeted interventions.

For example, women are more likely to develop dementia than men. Therefore, environmental and comorbid risk factors that more frequently affect women need to be quantified to determine their role in this association.

OSA is defined as episodes of blocked breathing in the upper airway leading to sleep disruption and hypoxia during these episodes. OSA, the prevalence of which increases with age, is an established risk factor for dementia. However, gender-specific prospective studies in a population-based cohort over extended periods are needed.

About the study

The current study included data from 18,815 American men and women age 50 and older who participated in the Health and Retirement Study (HRS). The average age of study participants was 60 and 61 years for men and women, respectively.

All study participants were dementia-free at the start of the study. A validated algorithm was used to identify new cases of dementia using objective tests of cognitive function.

Known OSA was recorded if a previous diagnosis of OSA was reported by the participant. Since 80% of people with OSA are never diagnosed, an alternative method was used to identify suspected OSA cases with a positive result in the STOP-Bang OSA screening tool.

These data were analyzed to identify differences in ten-year cumulative incidence of dementia between men and women stratified by age and presence of OSA.

Incidence of dementia

Dementia was reported in 9% and 8% of women and men, respectively, while the prevalence of known or suspected OSA was 48%. OSA was significantly more likely to occur in men at 68% compared to 31% of women. The mean educational status for participants with ALS was lower than those without ALS or at low risk of ALS.

Screening for OSA was positive for 29% of men and 30% of women with a previous diagnosis of OSA. In comparison, 10% of men and 7% of women had a diagnosis of OSA but tested negative with the STOP-Bang OSA screening tool.

The presence of OSA predicted a higher risk of dementia between 60 and 84 years of age. By age 80, women with CSA had a 4-7% higher cumulative incidence of dementia compared to adults without CSA, regardless of sex, compared to a 2.5% higher cumulative incidence in men.

The difference in dementia risk increased with age among women, but stabilized for men after an initial increase.

The population attributable risk ratio (PAR%) reflects the proportion of dementia cases attributable to OSA. The PAR% was 10.3% and 13.2% in women and men, respectively, reflecting the increased risk of CAD in men.

After adjusting for age, the risk of dementia with OSA became weaker but remained significantly higher compared with adults without OSA. The cumulative incidence among women with suspected or known OSA was 3.7% higher compared with 2.1% for men with known OSA.

Mechanism of dementia risk with OSA

OSA may increase the risk of developing Alzheimer’s disease (AD) and cognitive decline from any cause. This association has been attributed to the accumulation of tau protein and amyloid β42 (Aβ42).

OSA and sleep disturbance may also lead to chronic inflammation, which may then disrupt microglial function with Aβ42 accumulation, increase the risk of atherosclerosis, and lead to increased proinflammatory cytokines associated with brain shrinkage in AD .

OSA in women is more likely to cause reduced quality of life, poor sleep, fatigue, depression, cardiovascular disease (CVD) risk, and cognitive decline compared to men with OSA. The risk of OSA increases after menopause, with an increased age of onset of menopause being associated with a decreased risk of dementia.

conclusions

The current population-based longitudinal study involved the analysis of objective dementia data to estimate the ten-year risk of dementia in adults with ASD. Overall, the study findings suggest that OSA is a risk factor for dementia in older adults, with women at even higher risk than men.

The value of the observed association is increased by the careful search for undiagnosed OSA which constitutes 80% of these patients. These findings highlight the importance of identifying and treating OSA as a modifiable risk factor for the onset of dementia.

Similar findings have been reported in previous studies, suggesting that positive airway pressure (PAP) could protect OSA patients from mild cognitive impairment, as well as the onset and progression of AD.

Further research is needed with larger and more diverse cohorts using longitudinal follow-up and objective sleep data and better statistical techniques. These studies could provide important insights into the gendered relationships that develop over time between OSA and dementia. Identifying mediating factors could also lead to the development of targeted interventions to reduce the risk of dementia in older people with ASD.