Fig. 1.

Four-state survival model for cognition. We built a multi-state survival model (MSM) for cognitive functioning of the respondents, including cognitively unimpaired state, mild cognitive impairment (MCI) state, probable dementia state and death state. The arrows indicate the feasible instantaneous state-to-state transitions. In our model, respondents can transit between consecutive states in cognitive decline (i.e., successively progressing from cognitively unimpaired to, MCI to, probable dementia to death), revert from MCI to cognitively unimpaired, develop probable dementia from cognitively unimpaired, and transit to death from any state.