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, and 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.