Middle-age and older adults with chronic insomnia disorder are more likely to experience cognitive deficits, compared with people with insomnia symptoms alone or no sleep problems, according to a study published online in the journal Sleep.
Although previous studies have suggested links between insomnia and cognitive problems, results have been inconsistent, some study populations have been small, or people with chronic insomnia disorder have been lumped with those with insomnia symptoms and other contributing issues, such as chronic pain or anxiety, said researcher Thien Thanh Dang-Vu, MD, PhD, of Concordia University in Montreal, Canada.
“The purpose of our study was therefore to determine the precise link between chronic insomnia and cognitive function in a large sample of middle-aged and elderly people while also accounting for the possible effect of these other health issues,” he said.
The study included 28,485 adults age 45 and older from across Canada, who were divided into three groups:
- participants with probable chronic insomnia disorder, characterized by trouble falling asleep or staying asleep at least 3 nights a week for more then 3 months with an impact on daytime functioning, such as mood, attention, and concentration;
- participants with insomnia symptoms, characterized by the presence of insomnia symptoms with no apparent impact on daytime functioning; and
- participants with normal sleep.
All participants completed questionnaires, physical exams, and a battery of neuropsychological tests measuring cognitive function and sleep quality. Some 3.7% of the study population had probable chronic insomnia disorder, and 27.5% had insomnia symptoms alone.
“The individuals in the chronic insomnia group performed significantly worse on the tests compared to those from the other two groups. The main type of memory affected was declarative memory—the memory of items and events,” Dr. Dang-Vu said. “This was the case even after accounting for other factors, be they clinical, demographic or lifestyle characteristics, which may influence cognitive performance.”
“Does chronic insomnia predispose people to cognitive decline? Can these cognitive deficits be reversed with sleep disorder treatment?” he added. “There are many important questions that remain to be explored and that will have a major impact on the prevention and treatment of age-related cognitive disorders.”