Family History of Dementia in Old-Age Participants with Subjective Memory Complaints Predicts Own Risk for Dementia in a Longitudinal Multi-Center Cohort Study.

Background: Subjective memory complaints and family history of dementia are possibly intertwined risk factors for the own subsequent dementia risk and Alzheimer's disease. However, their interaction has rarely been studied.
Objective: To study the association between subjective memory complaints and family history of dementia with regard to the own subsequent risk of dementia.
Methods: Cross-sectional and longitudinal analyses over a follow-up period of up to 13 years were conducted in a population sample of participants without dementia at baseline (n = 3,256, mean age = 79.62 years), using group comparisons and Cox proportional hazards models.
Results: Cross-sectionally, participants with subjective memory complaints were significantly more likely to report family history of dementia. Longitudinally, family history of dementia (FH) was significantly associated with subsequent dementia in the subjective memory complaints (SMC) group, but not in those without SMC. A relative excess risk due to interaction analysis confirmed a significant FHxSMC-interaction.
Conclusions: Family history of dementia was a predictor of incident dementia in those with SMC, which can serve as an additional, clinically relevant criterion to gauge the risk of dementia in older-aged subjects with SMC with and without objective cognitive impairment.