Incident Mobility Disability, Mild Cognitive Impairment, and Mortality in Community-Dwelling Older Adults

Mobility disability and mild cognitive impairment (MCI) are common in aging and both are associated with risk of death. This study tested the hypothesis that risk of death differs by the order in which mobility disability and MCI occurred.

One thousand two hundred and sixty-two community-dwelling older adults were unimpaired at baseline and followed annually. Mobility disability was based on measured gait speed, and MCI was based on cognitive performance tests. A multistate Cox model simultaneously examined incidences of mobility disability and MCI to determine whether the order of their occurrence is differentially associated with risk of death.

The average age was 75.3 years and 70% were female. While mobility disability occurred more frequently than incident MCI, the subsequent risk of death was higher in participants who developed MCI alone compared to those who developed mobility disability alone (hazard ratio [HR] 1.70, p = 0.018). Of the participants who initially developed mobility disability, about half subsequently developed MCI that doubled their risk of death (HR 2.17, p < 0.001). By contrast, over two-third who developed MCI subsequently developed mobility disability, which did not further increase their risk of death.

Mobility disability occurs more frequently in community-dwelling older adults, but MCI is more strongly associated with mortality.