Subjective Memory Complaints are Associated with Incident Dementia in Cognitively Intact Older People, but Not in Those with Cognitive Impairment: A 24-Month Prospective Cohort Study

Objective: Although subjective memory complaints (SMCs) are considered a risk factor for incident dementia in older people, the effect might differ based on cognitive function. The aim of the present study was to investigate whether the effect of SMCs on the incidence of dementia in older people differed based on cognitive function. Design: A 24-month follow-up cohort study. Setting: Japanese community. Participants: Prospective, longitudinal data for incident dementia were collected for 3,672 participants (mean age: 71.7 years; 46.5% men) for up to 24 months. Measurements: Baseline measurements included covariates for incident dementia, SMCs, and cognitive function. Associations between SMCs, cognitive impairment, and incident dementia were examined using Cox proportional hazards models. Results: Incidences of dementia in the cognitively intact without SMC, cognitively intact with SMC, cognitive impairment without SMC, and cognitive impairment with SMC groups were 0.3%, 1.8%, 3.4%, and 4.8%, respectively. In the cognitively intact participants, SMCs were associated with a significantly higher risk of dementia (hazard ratio [HR]: 4.95, 95% confidence interval [CI]: 1.52-16.11, p = 0.008). Incident dementia with cognitive impairment was not significantly different based on SMC presence (p = 0.527). Participants with cognitive impairment in multiple domains had a significantly higher risk of incident dementia (HR: 2.07, 95% CI: 1.01-4.24, p = 0.046) Conclusion: SMCs were related with dementia in cognitively intact older people, but not in those with cognitive impairment. Multiple domains of cognitive impairment were associated with a higher risk of incident dementia.