Could self-reporting sleep duration become an important tool in the prediction of dementia?

Optimal sleep duration is increasingly recognized as an important determinant of overall health, including cognitive functioning. Studies often report a U- or J-shaped relationship between sleep duration and incident dementia or cognitive deterioration, whereas long sleep, the extremes of sleep duration, and the transition to long sleep were particularly detrimental. In preclinical studies, partial or complete sleep deprivation produced inflammation, oxidative stress, as well as increased tau hyperphosphorylation and amyloid-β burden. In humans, although the findings are less pronounced, they still highlight that transitioning to an excessive sleep duration is associated with neurodegeneration. Moreover, the association between sleep duration and dementia is complex and modified by genetic, psychosocial and lifestyle factors, along with psychiatric and somatic comorbidities.

The purpose of this perspective is to summarize the current knowledge on the association between sleep duration and dementia. It is based on a literature search for meta-analyses of prospective studies with sleep duration as an exposure and dementia as an outcome.

Sleep duration is a modifiable risk factor for dementia while long sleep may be an early sign of neurodegeneration. Therefore, self-reported sleep duration is an easy-to-use tool for detecting individuals who may be at risk for cognitive deterioration.