Summary: Sleeping nine hours or more per night is linked to poorer cognitive performance, especially in people with depressive symptoms, according to a Framingham Heart Study analysis by UT Health San Antonio researchers.
Key takeaways:
- Sleeping nine or more hours nightly is associated with reduced cognitive performance, particularly in memory, visuospatial skills, and executive function.
- The association between long sleep and cognitive decline is strongest in individuals with depressive symptoms, regardless of antidepressant use.
- No cognitive impact was found in participants using antidepressants without current depressive symptoms.
- Depression and long sleep may interact to increase risk for cognitive impairment, suggesting both are modifiable targets for prevention.
- Researchers recommend further longitudinal studies to clarify causal relationships between sleep, depression, and cognition.
There might be such a thing as getting too much of a good night’s sleep.
Sleeping nine hours or more per night is associated with worse cognitive performance, which is even more the case for those with depression, a study led by researchers at The University of Texas Health Science Center (UT Health San Antonio) shows.
They derived the results from an examination of sleep duration and cognition in 1,853 dementia- and stroke-free participants in the Framingham Heart Study, an ongoing community-based cohort study of residents in Framingham, Mass. This sleep duration-cognitive performance study focused on those ages 27 to 85 with a mean age of 49.8 years.
“Also, long-sleepers were more likely to report symptoms of depression,” says first author Vanessa Young, MS, clinical research project manager at the Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases at UT Health San Antonio, in a release. “Sleep may be a modifiable risk for cognitive decline in people with depression.”
“Long but not short sleep duration was associated with poorer global cognition and specific cognitive abilities like memory, visuospatial skills, and executive functions,” says senior author Sudha Seshadri, MD, founding director of the Biggs Institute, in a release. “These associations were stronger in people with depressive symptoms, regardless of antidepressant usage.”
Inconsistencies in Sleep-Cognition Research
According to the study, there is increasing recognition of the significance of sleep as a vital physiological process for brain health. Disturbances in sleep duration and patterns have been observed across lifespans and are present in both normal and pathological aging.
These disturbances contribute to an increased risk of cognitive deficits and Alzheimer’s disease. The Global Council on Brain Health recommends 7 to 8 hours of nightly sleep for adults to preserve brain health. Several studies have suggested that both excessive and insufficient sleep relative to the prescribed duration are linked to impairments in cognitive domains, including memory, attention, and the ability to manage and direct other mental processes, such as planning, problem-solving, and controlling impulses.
However, evidence has been marked by inconsistencies depending on the lifespan being examined, and on health differences such as depression. Depression, a modifiable risk factor for cognitive decline, often co-occurs with sleep disorders. The association between sleep disorders and depression is well established, with about 90% of people with depression reporting problems with sleep, the study notes.
Highlighted Study Findings
In the new research, the scientists investigated whether depression modified the associations between sleep duration and cognitive performance.
The Framingham participants were categorized into four groups:
- no depressive symptoms, no antidepressants;
- depressive symptoms without antidepressant use;
- antidepressant use without depressive symptoms;
- and depressive symptoms and antidepressant use.
They found that long sleep was associated with reduced overall cognitive function, with the strongest effects in those with depressive symptoms—using and not using antidepressants.
Weaker but significant effects were observed in those without depressive symptoms. No significant associations were observed in participants using antidepressants without depressive symptoms.
With that, they concluded that associations between sleep duration and cognitive performance are strongest in individuals with depressive symptoms, regardless of antidepressant use.
“Future longitudinal studies including large-scale, multi-modal approaches are needed to further elucidate the temporal relationship between sleep disturbances and cognitive changes,” the researchers said in their conclusion.
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