Longer sleep linked to neurodegeneration, cognitive decline, with depression as mitigator

Key takeaways:

• Researchers examined sleep, cognition and depression in a cohort of individuals across the lifespan.
• Longer sleep may signal neurodegeneration and cognitive decline, with depression as a modifiable risk factor.

PHILADELPHIA — Longer sleep duration may be linked to neurodegeneration as a likely risk factor for future cognitive decline and dementia, with depression also influencing sleep and cognitive deficit, according to a poster presentation.

“We are trying to identify what are modifiable risk factors that could delay or prevent the onset of Alzheimer’s disease and related dementias,” Vanessa M. Young, MS, project manager at the University of Texas Health Science Center in San Antonio, told Healio at the Alzheimer’s Association International Conference. “We know that sleep influences cognition.”

Because alterations in sleep patterns are common in older adults and decreased sleep has been associated with an increased risk for cognitive decline and dementia, Young and fellow researchers sought to investigate associations between sleep duration and cognition and whether depression acted as a mitigating factor in sleep duration and cognitive issues for persons across the lifespan.

Their study included 1,853 dementia- and stroke-free individuals from the Framingham Heart Study 3rd Generation, Omni 2 and New Offspring Spouse Cohorts (mean age, 49.84 years; 42.69% male; 95.78% white). All participants underwent a neuropsychological battery, as well as testing and assessments that examined global cognition, ability to handle individual tasks, sleep duration (short [6 hours or less], average [6 to 8 hours] and long [9 or more hours]), depression as measured by the 20-item Center for Epidemiologic Studies Depression Scale or by pharmacologic intervention.

The researchers used a pair of multivariable linear regression models for data analysis: one model stratified by age, sex, education, time between sleep questionnaires and neuropsychological testing and another combined results from the first model plus health-related factors such as hypertension, cholesterol, HDL and triglyceride levels, BMI and apolipoprotein E status.

The results showed a significant association with longer sleep and poor global cognition without a similar association between shorter sleep and global cognition.

Further, longer sleep duration was significantly associated with worse performance in executive function, visual and memory recall performance compared with those with average sleep in both models.

Data additionally show that depression was a likely contributing factor to poorer performance in global cognitive, visual and memory assessments, and that longer sleep duration was likely associated with cognitive deficits in those with depression compared with those without a depression diagnosis.

“We may have identified a subpopulation with potential mental disorders such as depression who may be more at risk of developing Alzheimer’s disease or cognitive deficits,” Young told Healio. “We need to include more sleep questions to understand their sleep quality.”