Researchers at The University of Texas Health Science Center at San Antonio (UT Health San Antonio) have identified a potential cognitive risk linked to excessive sleep. A study, published on April 21, 2025, in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, indicated that sleeping nine hours or more per night is associated with poorer cognitive performance, especially among individuals with depression.
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The findings are based on an analysis of 1,853 participants from the ongoing Framingham Heart Study, which examines heart health in residents of Framingham, Massachusetts. Participants, ages 27 to 85 with a mean age of 49.8 years, were assessed for sleep duration and cognitive abilities.
According to Vanessa Young, MS, the clinical research project manager at the Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases at UT Health San Antonio, those who reported longer sleep durations were also more likely to experience symptoms of depression. Young noted that sleep could be a modifiable risk factor for cognitive decline in individuals dealing with depression.
Sudha Seshadri, founding director of the Biggs Institute and the study's senior author, emphasized that extended sleep durations, not just insufficient sleep, correlated with declines in overall cognitive function and specific skills like memory and executive functions. These effects were found to be more pronounced in participants with depressive symptoms, regardless of whether they were using antidepressants.
The study underscores the importance of sleep as a critical element for brain health. Disturbances in sleep patterns can result in cognitive deficits and increase the risk for Alzheimer's disease. The Global Council on Brain Health recommends adults aim for 7 to 8 hours of sleep each night to support brain health. While both excessive and inadequate sleep has been linked to cognitive impairments, the relationship varies based on factors such as age and health conditions like depression, which notably co-occurs with sleep disorders.
The research categorized participants into four groups based on depressive symptoms and antidepressant use, revealing that long sleep was particularly detrimental to cognitive performance in those experiencing depressive symptoms. The conclusions suggest a need for future studies to explore the temporal relationship between sleep disturbances and cognitive changes in more detail.
This study highlights the complex relationship between sleep duration and cognitive health, particularly when depression is involved.