Short, long sleep duration worsen older adults’ amyloid beta burden, cognition

Results of a cross-sectional study published in JAMA Neurology found that sleep durations outside of a normal range worsened amyloid beta burden and cognition, underlining the importance of sleep in older adults.

“Focusing on cognitive decline, both short sleep (6 h/night) and long sleep (9 h/night) durations have been associated with worse outcomes,” Joseph R. Winer, PhD, of the department of neurology and neurological sciences at Stanford University School of Medicine, and colleagues wrote. “Although short sleep duration has been associated with greater brain [amyloid beta] burden in healthy older adults, which is believed to reflect a preclinical stage of [Alzheimer’s disease (AD)], the modest sample size of previous [amyloid beta] positron emission tomography (PET) imaging studies and the rarity of long sleep duration have precluded a thorough investigation of the distinct factors in short and long sleep duration while modeling the outcome of elevated [amyloid beta].”

The investigators sought to assess the links between brain amyloid beta burden and self-reported sleep duration as well as the demographic, cognitive and lifestyle variables among adults with normal cognition. They analyzed data of 4,417 participants (59% women; mean age, 71.3 years) of the Anti-Amyloid Treatment in Asymptomatic Alzheimer’s Disease study, which is ongoing in 67 sites across the U.S., Canada, Australia and Japan.

Participants were between 65 and 85 years old, had data available from an amyloid beta PET scan, had complete apolipoprotein E genotype data and were considered clinically normal according to a Clinical Dementia Rating score of zero and cognitively unimpaired according to a Mini-Mental State Examination score of 25 to 30, as well as a Logical Memory Delayed Recall test score of six to 18.

Participants self-reported nightly sleep duration, which investigators categorized as short (6 hours), normal (7 to 8 hours) and long sleep duration (9 hours), and the researchers compared this outcome with demographic characteristics, amyloid beta burden, objective and subjective cognitive function measures and lifestyle variables.

Results showed a linear association between self-reported shorter sleep duration and higher amyloid beta burden, as well as an association between short sleep duration and reduced cognition, largely in memory domains. Winer and colleagues observed no difference in amyloid beta between long and normal sleep duration groups; however, compared with normal sleep duration, they noted an association between both short and long sleep durations and higher BMI, depressive symptoms and daytime napping. Further, long sleep duration correlated with worse performance across multiple cognitive domains.

“The association between sleep duration and multiple intersecting health outcomes, such as greater [amyloid beta] burden, greater depressive symptoms, higher BMI and cognitive decline, highlight the importance of maintaining adequate sleep in late life,” the researchers wrote.