Influences of cohort differences and positive emotion on the relationship between cognition and disability in activities of daily living among older Mexican Americans

Background: Mexican Americans are the fastest growing minority group in the U.S. and older Mexican Americans are more likely to be living with chronic health conditions, such as diabetes and hypertension, compared to non-Hispanic white Americans. The rising prevalence of chronic conditions has contributed to an increased number of older Mexican Americans with disability in activities of daily living. Furthermore, recent cohorts of Mexican Americans exhibit greater disability than prior age-matched cohorts. Cognitive impairment is a known risk factor for disability. Positive emotion is associated with improved health outcomes. Little is known regarding its ability to modify the relationship between cognition and disability. Lastly, the driving factor behind the increase in disability for newer cohorts of Mexican Americans is unknown. This dissertation aims to explore the roles of cohort and positive emotion in changing the relationship between cognition and ADL disability. Methods: A systematic review was conducted on studies looking on the relationship between cognition and disability. We then did two retrospective cohort studies using waves 1 – 8 of the Hispanic Established Population for the Epidemiologic Study of the Elderly (EPESE). General estimation equations were used in three different models (cross-sectional, longitudinal, and predictive) to examine the independent and modifying effects of cohort, positive emotion, and cognition on risk of ADL disability in Mexican Americans aged 75 years and older. Results: The systematic review included 41 studies, 40 of which demonstrated significant relationship between cognition and disability. In the retrospective studies, there was not a significant difference between cohorts on the relationship between cognition and disability. The second cohort had a higher prevalence of disability, cognitive impairment, and chronic illnesses. The main effects of positive emotion were consistently protective against ADL disability and positive emotion was a significant modifier in the cross-sectional model. Cognitive impairment was consistently a strong risk factor for ADL disability. Conclusion: Further research is needed to identify why the newer cohorts have increased disability, as well as research to identify interventions that address cognitive and emotional needs; specifically interventions that are appropriate for Mexican Americans.