Sleep Disturbance, Physical Frailty, and Risk of Cognitive Impairment and Dementia in Older Adults with Subjective Cognitive Decline: A 10-Year Longitudinal Study

Background Subjective cognitive decline (SCD), a self-perceived decline in cognition without objective impairment, may represent an intermediate stage before clinical cognitive impairment develops. Sleep disturbance and physical frailty may reflect broader aging-related vulnerability and contribute to further cognitive progression in SCD. This study examined individual associations of sleep disturbance and physical frailty with 10-year incidence of cognitive impairment and dementia among older adults with SCD and explored whether physical frailty moderated the associations between sleep disturbance and cognitive outcomes. Methods Data were drawn from six waves of the Health and Retirement Study (HRS; 2010–2020). Independent analyses of sleep included 3,014 individuals with SCD at baseline, and frailty analyses used a subsample of 1,141 with frailty data. Sleep disturbance was assessed using a modified Jenkins Sleep Scale, and physical prefrailty/frailty was defined by the Fried frailty phenotype. Incident cognitive impairment and dementia were identified using validated HRS cognitive cutoffs. Discrete-time survival models adjusted for socio-demographics and health-related covariates. Results Sleep disturbance was not independently associated with incident cognitive impairment or dementia in fully adjusted models. Baseline physical prefrailty/frailty was significantly associated with increased odds of incident cognitive impairment (OR = 1.44, 95% CI: 1.15–1.80) and dementia (OR = 1.89, 95% CI: 1.23–2.93). Exploratory analyses suggested possible variation in the association between sleep disturbance and incident cognitive impairment by frailty status, but this finding should be interpreted cautiously. Conclusions Physical prefrailty/frailty is a significant factor of cognitive impairment in older adults with SCD, while the effect of sleep disturbance may vary by frailty status.