Parkinson’s Disease, Diabetes, Functional Decline and Cognitive Impairment: A Comparative Study of Elderly Mexican Americans and Non-Hispanic Whites

Abstract

Objective: Assess moderating effects of functional decline on the associations between late-life cognitive impairment (CImp) and diabetes and Parkinson’s disease (PD); including controls for Mexican-American ethnicity, education, life satisfaction, age, and sex. Methods: In-home interviews with 1,252 elderly Mexican-American (N = 799) and non-Hispanic white (N = 353) residents of El Paso County, Texas. CImp measured by MMSE, CLOXI and CLOXII; functional impairment (ADLimp) as impairment in 1-10 activities of daily living. Our hypothesis is that ethnicity will effect variance of diabetes, hence cognitive decline. Results: Logistic regression analyses--After controlling for effects of all above-cited variables, PD remains significantly associated with the three measures of CImp, including impairment in executive control function. Controlling for ADLimp does not extinguish the significant association between diabetes and CImp on any of the three measures. However, no significant degree of association between diabetes and CImp remains after other control variables (including Mexican-American ethnicity) have been added to the equation. Conclusions: 1) PD findings are statistically and clinically meaningful. After controlling for all other variables, the OR for respondents diagnosed with PD (compared to their non-diagnosed counterparts) is 1.42 for MMSE impairment (95% CI1.10-15.53); 4.12 for CLOXI impairment (95% CI 1.07-15.85); and 10.51 for CLOXII impairment (95% CI 2.55-43.41). 2) The connection between diabetes and CImp is problematic; our findings suggest that many of the earlierreported research findings linking diabetes with CImp may be an artifact of other intervening phenomena such as regional and ethnic differentials in prevalence rates for diabetes. 3) The relationship between CImp and ADLimp is strong and clinically meaningful; for each unit increase in ADLimp there is a corresponding 1.33 increase in odds for MMSE impairment (95% CI 1.15-1.55). For impairment on CLOX1 and CLOX2 the ORs are 1.22 (95% CI 1.05-1.42) and 1.21 (95% CI 1.03-1.42). 4) When coupled with other research findings, Mexican-American ethnicity may itself represent a risk factor for CImp. After controlling for effects all other variables, El Paso’s elderly Mexican Americans possess odds 2.46 times greater than those for NHWs in MMSE impairment (95% CI 1.42-4.25); 1.53 (95% CI 1.06-2.20) times greater for impairment in executive control function (CLOXI); and 2.35 times greater for impairment in ability to perform a simple copying task (1.35-4.09). 5) Our findings point to the importance of utilizing a number of different screening devices for assessment of cognitive function in order to increase the likelihood that results can be taken as valid, dependable, and clinically meaningful for elderly individuals a Hispanic ethnicity.