Sleep disturbances in midlife may lead to cognitive impairment: Study

People who suffer from sleep disturbances in midlife or as they age may be more likely to develop cognitive impairment than people who usually get plenty of uninterrupted rest, new research suggests.

Researchers examined data from four studies of the link between sleep and cognitive function, including two studies that followed almost 3,400 people for more than two decades, starting when they were in their 50s. In these two cohorts, people who suffered from nightmares and insomnia in middle age were more likely to experience cognitive impairment in old age than people who slept just fine earlier on.

When researchers examined these two studies as well as two others that started following people in their 70s and 80s, they found that insomnia and general sleep problems later in life were also associated with cognitive problems.

"While sleep disturbances are an important risk factor for cognitive decline, the good news is that it is a modifiable risk factor," said lead study author Shireen Sindi of the Karolinska Institute in Stockholm, Sweden, and Imperial College London.

"We can all have occasional sleeping difficulties, either due to high stress levels, caffeine or alcohol consumption or due to jet lag," Sindi said by email. "However, if a person experiences sleep disturbances on a chronic basis such as difficulties falling asleep, waking up during the middle of the night, waking up too early in the morning, or suffering from poor sleep quality, it is important to seek help from a health professional."

Even though sleep deprivation and difficulties with getting a good night's rest have long been linked to cognitive problems over time, less has been known about what precise type of sleep issues might impact brain function, researchers note in Sleep Medicine.

For the current study, researchers pooled data from four smaller studies of people in the general population in Sweden.

After just three to 11 years, sleep disturbances including insomnia were associated with lower scores on tests of



cognitive function, the study found.

When people had nightmares in middle age, this was associated with poor cognition later in life after 21 to 31 years of follow-up, the study also found.

This association, however, was partially explained by other factors that can impact both sleep quality and brain function - such as smoking, drinking and exercise habits as well as mental health issues.

One limitation of the study is that sleep problems were reported by participants, not measured objectively by researchers or doctors. Researchers also lacked data on certain risk factors for Alzheimer's disease, dementia and cognitive decline.

"There are some fascinating links between Alzheimer's disease and sleep quality, most likely due to a complex bidirectional relationship between poor sleep and a greater amount of amyloid, one of the key proteins that accumulates in Alzheimer's disease," said Dr. Kristine Yaffe, a psychiatry researcher at the University of California, San Francisco, who wasn't involved in the study.

"Other possible mechanisms include brain vascular changes, inflammation and shared genetic causes," Yaffe said by email.

A wide variety of treatments may help address sleep disturbances, including medication, cognitive behavior therapy and lifestyle changes to eliminate things like cigarettes and alcohol and focus on healthy eating habits and a regular exercise routine, Sindi advised.

"Numerous treatments and strategies are available to help with sleeping problems, and the optimal solution will differ according to the underlying problem and its causes," said Matthew Pase, a researcher at the University of Technology in Melbourne and the Boston University School of Medicine.

"No one sleep therapy is a cure for all," Pase said by email. "It is still unclear whether treatment of sleep problems can reduce the likelihood of future cognitive decline, but improving sleep is likely to have beneficial effects on other aspects of general wellbeing and health."