The association between general medical health and course of cognition, function, and neuropsychiatric symptoms in the cache county dementia progression study

Abstract

A number of studies suggest a link between health status and dementia course in individuals with Alzheimer's disease (AD). We investigated the relationships between measures of health and changes in cognition, function, and neuropsychiatric symptoms in a population-baed study of incident AD. We used data from the population-based Cache County study of memory and aging (CCSMA). The sample included 335 individuals with incident AD who were followed for up to eleven years. Measures of health status at each visit included the General Medical Health Rating (GMHR), number of comorbid medical conditions, and number of non-psychiatric medications. Dementia outcomes included the Mini-Mental State Examination (MMSE), Clinical Dementia Rating – sum of boxes (CDR-sb), and the Neuropsychiatric Inventory (NPI). Two types of longitudinal mixed effects were fit: in the first, differences in course over time on the dementia outcomes was modeled as a function of baseline health; in the second, outcomes at each timepoint were measured as a function of health at the same timepoint. All models were adjusted for sex, age, education, dementia duration at baseline, and APOE genotype. individuals demonstrated both improvements and worsening of their health status over time. Neither GMHR nor comorbidities, and non-psychiatric medications at baseline were associated with differences in rates of decline. Over time, lower GMHR ratings at a given visit were associated with worse outcomes at that same visit (MMSE: β = –1.07 p = 0.01; CDR-sb: β = 1.79 p < 0.001; NPI: β = 4.57 p = 0.01). Given that time-varying GMHR, but not baseline GMHR, was associated with each of the outcomes it seems likely that the effect is a dynamic one, but potentially modifiable. Further study, including randomized trials of dementia care models, is needed to establish the direction of causality and the efficacy of improving health as a means of ameloriating the effects of AD.