Researchers at the University of Texas at San Antonio (UT Health San Antonio) found that sleeping nine hours or more is associated with poorer cognitive function, particularly in individuals with depression. The study’s findings were published in the medical journal Alzheimer’s & Dementia (A&D).
The study was conducted as part of the Framingham Heart Study and included 1,853 volunteers aged 27 to 85, with an average age of approximately 50. The researchers aimed to determine how sleep duration affects brain function, particularly in relation to the presence or absence of depressive symptoms.
The authors emphasize that both insufficient and excessive sleep can negatively impact memory, attention, and decision-making ability. According to the Global Brain Health Council, the optimal amount of sleep for adults is seven to eight hours.
The study examined the relationship between sleep and depression. Participants were divided into four groups based on the presence and severity of depressive symptoms. The results showed that among individuals with depression—regardless of whether they were taking medication—longer sleep duration was associated with greater cognitive decline.
Cognitive decline was also observed among participants without depression, but to a lesser extent. Notably, individuals taking antidepressants without exhibiting depressive symptoms did not experience statistically significant changes.
Researchers note that sleep disorders and depression are often closely linked: approximately 90% of individuals with depression report experiencing sleep problems.
