Too much sleep can equal poorer brain function

Sleeping long has a negative effect on brain performance, especially in people who are depressed, according to the findings of a new study. It suggests that sleep might be a modifiable risk factor for cognitive decline in people with depression.

Researchers have been investigating the relationship between sleep duration and health, particularly brain health, for some time. Indeed, the Global Council on Brain Health (GCBH) recommends that older adults sleep for an average of seven to nine hours a night to maintain brain health and functioning.

New research led by the University of Texas Health Science Center at San Antonio (UT Health San Antonio) has examined whether the association between sleep duration and brain, or cognitive, performance was affected by depression.

“Long but not short sleep duration was associated with poorer global cognition and specific cognitive abilities like memory, visuospatial skills and executive functions,” said the study’s senior author, Sudha Seshadri, MD, founding director of the Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases at UT Health San Antonio. “These associations were stronger in people with depressive symptoms, regardless of antidepressant usage.”

The researchers obtained data from 1,853 participants involved in the long-running Framingham Heart Study (FHS). The participants, 42.7% of whom were male, were dementia- and stroke-free, and had a mean age of almost 50. Participants reported the number of hours they typically slept, which was categorized as short (less than six hours), average (between six and nine hours), or long sleep duration (greater than nine hours). The participants also underwent neuropsychological testing to measure cognitive function.

Depression was also measured, and participants were divided into four groups: those not using antidepressants and without depressive symptoms (the control group); those using antidepressants and without depressive symptoms; those not using antidepressants with depressive symptoms; and those using antidepressants with depressive symptoms.

They found that long sleep duration was associated with reduced overall cognitive function, with the strongest effects seen in participants with depressive symptoms, both in those using and not using antidepressants. Weaker but still significant effects were observed in those without depressive symptoms.

“Also, long-sleepers were more likely to report symptoms of depression,” said Vanessa Young, MS, clinical research coordinator at the Biggs Institute and the study’s lead author. “Sleep may be a modifiable risk for cognitive decline in people with depression.”

The study’s cross-sectional design didn’t allow the researchers to determine the causality of the relationship between sleep and cognitive performance. Additionally, the self-reporting of sleep duration may have introduced recall biases, including the overestimation of actual sleep time versus time spent in bed. And, the inclusion of predominantly White participants limits the study’s generalizability to more diverse populations.

“Future longitudinal studies including large-scale, multi-modal approaches are needed to further elucidate the temporal relationship between sleep disturbances and cognitive changes,” they said.

The study was published in the journal Alzheimer’s Association.

New Atlas