Adults who sleep 6 hours or less increase their dementia risk by 30% according to a recent study published in Nature Communications.
Existing studies that assess sleep duration over more than 10 years primarily involve adults age 65 and older. The researchers wanted to assess the relationship between sleep and dementia beginning at age 50.
The researchers used data from the Whitehall II cohort study that includes British civil servants and spans 30 years. They assessed the association between sleep duration and dementia at age 50, 60, and 70. They also looked at the relationship between mental disorders in midlife, sleep duration, and dementia.
The study included data from 10,308 individuals — 7,959 had data on sleep duration at age 50.
Among the participants with sleep data, 521 developed dementia over a mean follow-up period of 24.6 (SD = 7.0) years. The follow-up was 25.7 (SD = 5.1) years in dementia cases and 24.6 (SD = 7.1) years in noncases. Most dementia cases were diagnosed after age 70, with a mean age at diagnosis of 77.1.
The lowest incidences of dementia occurred in adults who slept 7 hours per night, regardless of age.
An association between dementia and short sleep at 50 (hazard ratio (HR) = 1.22, 95% CI = 1.01–1.48) and 60 years (HR = 1.37, 95% CI = 1.10–1.72) was observed. “There was no clear evidence of an association between long sleep duration and incident dementia,” the researchers reported. The association between short sleep duration and dementia is not attributable to mental health, the study researchers found.
Participants in the cohort were employed and healthier than the general population were both limitations of this study.
“Short sleep duration in midlife is associated with an increased risk of dementia,” the study researchers concluded. “Public health messages to encourage good sleep hygiene may be particularly important for people at a higher risk of dementia.”
Sabia S, Fayosse A, Dumurgier J, et al. Association of sleep duration in middle and old age with incidence of dementia. Nat Commun. Published April 20, 2021. doi:10.1038/s41467-021-22354-2