Long Sleep Duration Linked to Poorer Cognitive Performance

Getting too much sleep each night may affect cognitive function, especially in adults with depression, according to a study in Alzheimer’s & Dementia.

Vanessa M. Young, M.S., of the University of Texas Health Science Center at San Antonio, and colleagues examined data from 1,853 Framingham Heart Study participants ranging from 27 to 85 years old (mean age of 50) who did not have dementia or stroke. They asked the participants about antidepressant use and assessed the participants for depression. They then divided the participants into four groups:

• No depressive symptoms, not taking antidepressants
• Depressive symptoms, not taking antidepressants
• No depressive symptoms, taking antidepressants
• Depressive symptoms, taking antidepressants

In each group, participants self-reported the number of hours they slept per night and were categorized as having short sleep (six hours or less), average sleep (between six and nine hours), and long sleep (nine hours or more). They also took a battery of tests to assess their cognitive performance.

Overall, compared with participants with average sleep, those with long sleep had poorer performance in global cognition, executive function, visuospatial memory, and verbal learning/memory tasks.

“These findings suggest that sleeping ≥ 9 hours per night is associated with cognitive differences equivalent to 6.5 years of brain aging,” Young and colleagues wrote.

Among individual patient groups, the strongest negative associations between long sleep and cognition were among individuals with depressive symptoms, regardless of antidepressant usage. There was a smaller effect of long sleep among adults with no depression and no antidepressant use, while no cognitive effect of long sleep was seen in adults who took antidepressants but had no depressive symptoms.

Young and colleagues suggested that antidepressant use among those with no depressive symptoms may reduce nighttime awakenings, improve restorative sleep, or stabilize sleep–wake timing. “However, whether this observation reflects antidepressant treatment, symptom remission, or other unmeasured aspects of sleep health remains unclear, given the limitations of our sleep measures.”

The researchers also did not find a statistically significant relationship between short sleep and cognitive performance.

“These results diverge from some studies that have identified short sleep as a risk factor for cognitive impairment,” they wrote. “The precision of this association may increase with greater statistical power or in older populations in which short sleep and cognitive impairment may be more prevalent.”

For related information, see the Psychiatric News article “Poor Quality Sleep in Midlife Linked to Poor Cognition 11 Years Later.”

(Image: Getty Images/iStock/HomePixel)

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Extending Weekend Sleep May Reduce Risk of Death in Some Adults Under 65

Adults under the age of 65 who regularly sleep five or less hours on weeknights but more hours on weekend nights appear to have a lower risk of death than those who sleep five or less hours a night on weekends, according to a study in the Journal of Sleep Research.

“The results imply that short (weekday) sleep is not a risk factor for mortality if it is combined with a medium or long weekend sleep,” Torbjörn Åkerstedt, Ph.D., of the Karolinska Institutet in Stockholm and colleagues wrote. “This suggests that short weekday sleep may be compensated for during the weekend, and that this has implications for mortality.”

To examine the association of both weekday and weekend sleep duration on overall mortality, Åkerstedt and colleagues tracked mortality in a cohort of 38,015 Swedish adults aged 18 and over from October 1997 through the end of 2010. At the start of the study, each participant was asked to assess both the number of hours he or she regularly slept on a workday night and a weekend night. The researchers relied on the Swedish National Register of Death to obtain information on date of death and the underlying causes of death in participants from the cohort study.

Of the 38,015 people included in the analysis, 3,234 deaths occurred during study. Statistical analysis revealed that among individuals under age 65, short weekend sleep was associated with a significant 52% higher mortality rate compared with those who slept seven hours on the weekend, while no association was found for long (nine or more hours) weekend sleep. Additional analysis revealed that consistently sleeping five or less hours on both weekdays and weekends was associated with a 65% higher mortality rate compared with consistently sleeping six or seven hours a night, and consistently sleeping eight or more hours was associated with a 25% higher mortality rate. The associations between weekend sleep or weekday/weekend sleep durations and mortality were not observed among individuals aged 65 and older.

“In conclusion, our findings indicate that mortality is increased when both weekday and weekend sleep is short or when both are long in subjects below the age of 65 years. However, when weekend sleep is extended after short weekday sleep, no association with mortality is seen,” the authors wrote. “We suggest that this may reflect positive effects of compensatory sleep. However, this issue needs to be addressed in longitudinal studies of changes in sleep duration and their link to mortality.”

For related information on this topic, see the APA Publishing book Sleep Disorders and Psychiatry, edited by Daniel J. Buysse, M.D.

(Image: iStock/andresr)

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