For women with multiple sclerosis who report cognitive dysfunction—one of the most common and disabling symptoms of the disease—sleep disorders such as insomnia and sleep apnea may contribute to the perceived decline, a Michigan Medicine study suggests.
Researchers analyzed data from over 60,000 women using the 2013 and 2017 waves of the Nurses’ Health Study, a long-term study that focuses on risk factors for chronic diseases in women. Using composite scores of self-reported diagnoses and symptoms, they found that women with multiple sclerosis were more likely than those without multiple sclerosis to report sleep disorders, including obstructive sleep apnea, insomnia, and sleepiness.
Results published in Multiple Sclerosis Journal also reveal that sleep disorders identified in 2013 contributed to cognitive problems reported by women with multiple sclerosis in 2017, including the ability to follow instructions and conversations, as well as memory. Insomnia mediated over 10% of these outcomes, and sleep apnea accounted for 34% of the total effect between multiple sclerosis and the ability to follow instructions.
“Sleep disorders have gained substantial recognition for their role in cognitive decline, which affects up to 70% of people with multiple sclerosis,” says lead author Tiffany Braley, MD, director of the Multiple Sclerosis/Neuroimmunology Division and multidisciplinary MS Fatigue and Sleep Clinic at University of Michigan Health, in a press release. “Our results highlighted important pathways between sleep and perceptions of cognitive function in women with MS. We have previously identified important associations between objective cognitive performance and sleep in people with MS, but little is known about how sleep and MS interact together to impact long-term cognitive outcomes, particularly among women who are less likely to be diagnosed with sleep disorders.”
Past studies have found that people with multiple sclerosis have a high burden of sleep disorders that have been shown to affect quality of life. As people with multiple sclerosis are at risk for sleep and cognitive problems, researchers sought to examine cognitive outcomes among nurses with multiple sclerosis and sleep disorders.
“With this longitudinal study design, we are able to better estimate the burden of sleep disorders among nurses, compared to health care claims data of similar size, which include diagnosed people with sleep disorders,” says senior author Galit Levi Dunietz, PhD, an epidemiologist and associate professor in the Department of Neurology’s Division of Sleep Medicine, in a press release. “However, as sleep disorders are frequently underdiagnosed, health care claims data miss many people with sleep disorders who were not evaluated for these conditions.”
Interventions to delay cognitive decline in multiple sclerosis may be most effective in pre-symptomatic or early symptomatic stages, says Braley in a press release.
“Perceived cognitive decline, even in the absences of objective changes, could be an important window of opportunity to identify treatable exacerbating factors, such as sleep disorders,” she says in the release.
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