A common but underdiagnosed sleep disorder contributes to the development of dementia in adults; especially women, a study from Michigan Medicine suggests.
Researchers discovered this by examining survey and cognitive screening data from more than 18,500 adults to determine the potential effect of known or suspected obstructive sleep apnea on dementia risk.
Obstructive sleep apnea is a chronic sleep disorder characterized by episodes of disturbed or restricted breathing during sleep.
For all adults aged 50 and over who have known obstructive sleep apnea or its symptoms -; because people often don’t know they have the problem -; was associated with a greater chance of having signs or a diagnosis of dementia in the coming years.
Although the overall difference in these dementia diagnoses never exceeded 5%, the association remained statistically significant even after researchers took into account many other factors that can influence dementia risk, such as race and education.
At all age levels, women with known or suspected sleep apnea were more likely than men to be diagnosed with dementia.
In fact, the number of dementia diagnoses decreased among men and increased among women as they got older.
The results are published in SLEEP Progress.
“Our findings provide new insight into the role of treatable sleep disorder on long-term cognitive health at the population level for both women and men,” said first author Tiffany J. Braley, MD, MS, neurologist, director of the Multiple Sclerosis/ Department of Neuroimmunology and co-founder of the multidisciplinary MS Fatigue and Sleep Clinic at University of Michigan Health.
Reasons for the sex-specific differences in the diagnosis of dementia based on sleep apnea status are not yet known, according to researchers. However, they offer several possible explanations.
Women with moderate sleep apnea may be at greater risk for cardiovascular disease and more likely to experience insomnia, both of which can negatively impact cognitive function.
Estrogen begins to decline as women transition to menopause, which can affect their brains. During that time, they are more susceptible to memory, sleep, and mood changes that can lead to cognitive decline. Sleep apnea increases significantly after menopause but remains underdiagnosed. We need more epidemiological studies to better understand how sleep disorders in women affect their cognitive health.”
Galit Levi Dunietz, Ph.D., MPH, co-author, associate professor in the Department of Neurology and the Department of Sleep Medicine at the University of Michigan
Six million Americans have been officially diagnosed with sleep apnea, but the condition is believed to affect nearly 30 million people.
In a 2024 report, a Lancet The Commission has identified several modifiable risk factors that together account for approximately 40% of global dementia.
Although sleep was not included as an official risk factor, the committee noted that sleep apnea “may be related to dementia” and to consider adding screening questions about dementia for people with the sleep disorder.
Other modifiable risk factors for dementia include cardiovascular disease and mental health problems, both of which can be worsened by untreated sleep apnea.
“These potential damages caused by sleep apnea, many of which threaten and degrade cognitive performance, highlight the importance of early diagnosis and treatment,” Braley said.
“Obstructive sleep apnea and the resulting sleep deprivation and fragmentation are also associated with inflammatory changes in the brain that may contribute to cognitive impairment.”
The Michigan Medicine study used existing data from the Health and Retirement Study, an ongoing study representative of Americans age 50 and older.
“This study design cannot fully prove that sleep apnea causes dementia – that would likely require a randomized trial, over many years, to compare the effects of sleep apnea treatment with the effects of no treatment,” says co-author Ronald D. Chervin, MD, MS, director of the Division of Sleep Medicine in the Department of Neurology at UM Health.
“Since it may be a long time, if ever, before such research takes place, backward-looking analyzes such as ours, within large databases, could be among the most informative in the coming years. In the meantime, the results provide new evidence that physicians and patients should consider the possibility that untreated sleep apnea causes or worsens dementia when making decisions about sleep apnea testing and treatment.”
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Magazine reference:
Braley, T.J. et al. (2024). Gender-specific dementia risk in known or suspected obstructive sleep apnea: a 10-year longitudinal population-based study. SLEEP Progress. doi.org/10.1093/sleepadvances/zpae077.