Could Sleep Apnea in Millions of Americans Increase Dementia Risk?

People with obstructive sleep apnea may be more likely to develop dementia, and the risk may be greater for women, a new study has found.

The new research raises questions about how obstructive sleep apnea—which lowers a person’s oxygen levels as they sleep—might affect brain health over time.

“Obstructive sleep apnea is a common, under-diagnosed yet treatable condition that is associated with important pathological changes in the brain,” study author Tiffany Joy Braley, MD, associate professor of neurology and cofounder of the MS Fatigue and Sleep Clinic at University of Michigan Health, told Health. “[These] overlap with many brain changes seen in people with cognitive decline and dementia.”

Beyond simply finding a link between sleep apnea and dementia risk, the researchers also found that this association is more pronounced in women. Experts still aren’t exactly sure why that is, though it could have something to do with women’s already elevated risk of cognitive issues.

“There are several reasons why women may be at higher risk for dementia, including their longer life expectancy, differences in health behaviors, and social determinants of health,” study author Galit Levi Dunietz, PhD, MPH, associate professor in the University of Michigan Department of Neurology and Division of Sleep Medicine, told Health.

The study was published last month in the journal Sleep Advances.

Here’s what experts had to say about the connection between obstructive sleep apnea and dementia and how to protect your cognitive health if you have a sleep disorder.

This isn’t the first study to establish a link between obstructive sleep apnea and dementia, experts said. However, “this new study adds to the conversation by providing [10 years of] longitudinal data for 18,815 subjects,” Nitun Verma, MD, MBA, a spokesperson for the American Academy of Sleep Medicine, told Health.

The research included participants from the Health and Retirement Study (HRS), which is a nationally representative group of U.S. adults. At the time the study began in 1992, the participants were over age 50 and were all dementia-free.

The researchers then tracked confirmed cases of dementia among the study participants and recorded who was diagnosed with obstructive sleep apnea or reported having symptoms.

This allowed researchers to “determine whether pre-existing signs of [obstructive sleep apnea]—even in the absence of a clinically-given diagnosis—predict the likelihood of developing future dementia,” said Braley.

This decision to also include participants with suspected sleep apnea in the analysis is also significant, as many Americans who have the disorder haven’t been diagnosed. In fact, it’s estimated that about 30 million Americans have sleep apnea, though only about 6 million Americans have received a diagnosis.

A few factors could explain this. For one, sleep apnea symptoms often develop gradually and go unnoticed, said Verma. “The most common symptoms, like snoring and daytime sleepiness, are easy to dismiss or are attributed to other causes.” Additionally, many Americans may not be able to undergo a sleep study, which is needed to diagnose the condition, experts said.

After completing their analysis, the researchers found that, by age 80, the incidence of dementia was 4.7% higher among women with confirmed or suspected sleep apnea and 2.5% higher among men with a confirmed or suspected case.

“Relative to adults who did not have known or suspected obstructive sleep apnea, adults with obstructive sleep apnea have a higher risk for future dementia, particularly women,” Braley said.

Though it wasn’t investigated in the study, experts have a few theories as to why sleep apnea could influence the risk of dementia.

For one, having a sleep disorder makes it challenging to get good-quality sleep. This can raise the risk of cognition issues.

“Recent evidence suggests that sleep deprivation or insufficient sleep—[both of which are] consequences of obstructive sleep apnea—are associated with increased accumulation of pathological biomarkers associated with Alzheimer’s,” Braley said.

Another potential explanation is that sleep apnea and sleep deprivation could alter immune system function, making it harder for the body to get rid of toxic substances in the brain that have been linked to dementia, she added.

As for why the association between sleep apnea and dementia was more pronounced among women as compared to men, hormonal differences may play a role, Dunietz explained.

“As women transition to menopause, they experience a decline in estrogen that could interact with sleep problems to increase dementia risk,” she said.

Lack of access to competent care and gender disparities in healthcare could also be to blame.

“A significant factor is that a woman can be under-diagnosed or misdiagnosed, and this can lengthen the duration of suffering the consequences of not being treated [for sleep apnea],” Verma said. “Additional research is needed to better understand and analyze the relationship.”

The new study highlights the need to seek treatment for obstructive sleep apnea if you suspect you have the condition.

“Identifying and addressing this impactful and treatable condition could offer another step toward supporting cognitive health,” Braley said.

Common signs of sleep apnea include snoring, daytime sleepiness, fatigue, concentration issues, headaches, or waking up frequently in the middle of the night to use the bathroom.

It’s important to remember that, for now, there’s no evidence to suggest that sleep apnea itself causes dementia, said Robson Capasso, MD, professor of otolaryngology and chief of sleep surgery at Stanford Health Care.

“People should not be panicked about this,” he told Health.

Though more research needs to be done on the connection between sleep apnea and brain health in particular, getting bad sleep is a cause for concern—sleep deprivation has been linked to obesity, heart health issues, and type 2 diabetes.

So, if possible, Capasso said, people should try to curb or address any modifiable risk factors for sleep apnea, including excessive drinking, smoking cigarettes, and obesity.

If you’ve already been diagnosed, it’s important to track your symptoms and communicate with your doctor if they don’t improve or they get worse, Verma added.

“Early recognition, diagnosis, and effective treatment of obstructive sleep apnea are crucial, as they may help mitigate adverse health outcomes,” he said.