Cognitive trajectories in older adults and associated mortality and predictors

To test the hypotheses that declining cognitive aging trajectories would increase mortality risk and that predictors of mortality would differ between trajectory groups.

This is a sub-study of the ZARADEMP project studying dementia and depression in older adults aged 55 years or more, conducted in Zaragoza, Spain, including 2403 cognitively healthy individuals who had completed at least three of the four waves in a 12-year follow-up. The three cognitive trajectories previously identified were based on the Mini-Mental State Examination (MMSE). Mortality information obtained from the city's official population registry was registered up to 6 years after the end of the fourth wave of the study. Cox proportional hazard regression analyses for analyzing the risk of death were performed globally and for each cognitive trajectory.

At follow-up, 42.4% of the participants had died. Individuals in class 2-moderate-stable and in class 3-low-and-declining had a 24% and 96%, respectively, higher risk of mortality than those in class 1-high-to-moderate. Those younger and women showed significant lower risks of death in all the classes. Being single, with diabetes, dependency in basic Activities of Daily Living, ex-drinkers, smokers, and ex-smokers increased the risk in class 2. Hypertension showed a higher risk of death in the high-to-moderate group. In the low-and-declining trajectory, anxiety nearly tripled the risk of death.

Trajectories with cognitive decline are associated with higher mortality, with the risk of death showing a gradient. Predictors of mortality differ by cognitive trajectory; the differences being observed even among the cognitively healthier groups.