Mutual effects of sleep duration and traits on the risk of dementia: A prospective study in the UK Biobank

Background Both sleep duration and traits significantly influence cognitive health, making it crucial to identify optimal sleep patterns for preventing dementia. Objective To investigate the mutual effects of sleep duration and sleep traits on dementia risk. Methods This prospective study analyzed data from 359,505 participants in the UK Biobank, with baseline data collected between 2006–2010. Sleep patterns were assessed by constructing composite indicators through pairwise combinations of self-reported sleep duration and traits, including ease of getting up in the morning, chronotype, napping, daytime dozing, and use of sleep-related medications. The association between sleep patterns and dementia incidence was evaluated using Cox proportional hazards models during a mean follow-up period of 13.63 years. Results During the follow-up, 5123 participants developed dementia. In fully adjusted models, both short (≤6 h) and long (≥9 h) sleep durations, along with unfavorable sleep traits (hard or easy getting up, morning chronotype, habitual napping, dozing, sleep-related medications use), were significantly associated with increased dementia risk (p < 0.05). Notably, long sleep duration combined with evening chronotype (HR = 1.45, 95%CI: 1.15–1.83), habitual dozing (HR = 1.57, 95%CI: 1.18–2.09), or hypnotic use (HR = 2.71, 95%CI: 1.77–4.13) exhibited the highest risks compared to optimal sleep duration with corresponding alternative sleep traits. Similarly, short sleep duration combined with habitual napping carried the highest risk of dementia (HR = 1.54, 95%CI: 1.27–1.88). Conclusions Both sleep duration and traits are associated with dementia risk, particularly when abnormal duration interacts with unfavorable traits. These findings underscore the necessity of incorporating comprehensive sleep pattern assessments into dementia prevention strategies.