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Abstract:
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We evaluate death as a competing event to the development of dementia in a longitudinal study of the cognitive status of elderly subjects. A multi-state Markov model with three transient states: intact cognition, mild cognitive impairment, and global impairment and one absorbing state, dementia, models the cognitive panel data; transitions among states depend on four covariates age, education, prior state and the presence/absence of an apolipoprotein E-4 allele. A Weibull model is fit to survival from death based on age at entry and E-4 status. A shared random effect correlates this survival time with the transition model. Simulation studies determine the sensitivity of the maximum likelihood estimates to the violations of the Weibull assumption. Results are illustrated with an application to the Nun Study, a longitudinal cohort of 672 participants 75+ years of age at baseline.
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