Previous research suggests that both excessive and insufficient sleep relative to the recommended 7-8 hours per night is linked to impaired cognition. Research also suggests that depression may modify the relationship between sleep and cognition. Around 90% of people with depression also report problems with sleep.
In the current study, researchers investigated whether depression affects the link between sleep duration and cognitive performance. To do so, they examined data from 1853 participants from the Framingham Heart Study, an ongoing community-based cohort study of residents in Framingham, Massachusetts. Patients were dementia and stroke-free and had an average age of around 50 years old.
They were categorized into four groups: those without depressive symptoms who did not use antidepressants, those with depressive symptoms who did not use antidepressants, those using antidepressants without depressive symptoms, and those who had depressive symptoms and used antidepressants. Short sleep duration was defined as less than 6 hours, average sleep between 6 and 9 hours, and long sleep: 9 hours or more.
Ultimately, the researchers found that sleeping more than or equal to 9 hours per night was linked to worse cognitive performance, and that the effect was strongest among those with depressive symptoms, whether or not they used antidepressants. Weaker yet significant effects were also observed in those with no depressive symptoms. No significant associations were reported among those who used antidepressants without depressive symptoms.
The findings suggest that sleep may be a modifiable risk for cognitive decline in people with depression, wrote the researchers in their study.
“Future longitudinal studies including large-scale, multi-modal approaches are needed to further elucidate the temporal relationship between sleep disturbances and cognitive changes,” they added.
Sources: Science Daily, Alzheimer’s & Dementia