OBJECTIVES: To examine the effects of caring for a spouse with dementia on the caregiver's risk for incident dementia.

DESIGN: Population-based study of incident dementia in spouses of persons with dementia.

SETTING: Rural county in northern Utah.

PARTICIPANTS: Two thousand four hundred forty-two subjects (1,221 married couples) aged 65 and older.

MEASUREMENTS: Incident dementia was diagnosed in 255 subjects, with onset defined as age when subject met Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised, criteria for dementia. Cox proportional hazards regression tested the effect of time-dependent exposure to dementia in one's spouse, adjusted for potential confounders.

RESULTS: A subject whose spouse experienced incident dementia onset had a six times greater risk for incident dementia as subjects whose spouses were dementia free (hazard rate ratio (HRR)=6.0, 95% confidence interval (CI)=2.2-16.2, P