Napping Characteristics and Incident Dementia: Results From The National Health and Aging Trends Study.

BACKGROUND: Whether daytime napping may be a risk factor for dementia, in addition to nighttime sleep disturbances, remains unclear. This study investigated longitudinal associations of napping characteristics with incident dementia among U.S. older adults. METHODS: Data came from the National Health and Aging Trends Study (NHATS). Napping characteristics were self-reported in a sleep module at round 3 (2013), including (1) frequency (non-napper, infrequent, frequent); (2) intention (non-napper, intentional, unintentional); (3) duration (non-napper, ≤30 minutes, >30 minutes). Dementia classification was established at each round using a validated algorithm and possible/probable dementia served as our outcome. We included 995 participants free of possible/probable dementia at round 3 who were followed up to round 13 (2023). Discrete-time complementary log-log models were used for hazard ratio (HR) of incident possible/probable dementia associated with napping characteristics, adjusting for demographic, health, and sleep variables (duration, daytime sleepiness, obstructive sleep apnea risk). RESULTS: When compared to non-nappers, frequent nappers had 1.48 times the hazard of developing incident possible/probable dementia (95% confidence interval [CI]: 1.14, 1.94). Unintentional napping was associated with incident possible/probable dementia (HR = 1.39, 95% CI: 1.06, 1.81). No associations were found for infrequent or intentional napping. Napping ≤30 minutes was associated with possible/probable dementia (HR = 1.40, 95% CI: 1.06, 1.85), but the association of napping >30 minutes was attenuated with additional adjustment for sleep variables (HR = 1.28, 95% CI: 0.96, 1.69). CONCLUSIONS: Daytime napping may be a modifiable risk factor for dementia if supported by further evidence. Future studies with detailed napping characteristics and longer follow-up are needed.