The interaction of cognitive and emotional status on subsequent physical functioning in older mexican americans: findings from the Hispanic established population for the epidemiologic study of the elderly.

BACKGROUND: Optimal mental health (cognitive and emotional functioning) is an important factor for maintaining physical function. This study investigated the effects of cognitive and emotional status on subsequent lower body function in a population-based sample of older Mexican Americans.
METHODS: A 2-year prospective cohort study included Mexican Americans aged 65 and older who scored 18 or higher on the Mini-Mental State Examination (MMSE) at baseline interview and for whom complete data on a summary performance measure of lower body function were available at the 2-year follow-up interview (n = 2068). In-home interviews in 1993-1994 and 1995-1996 assessed sociodemographic variables, physical health conditions, cognitive function, emotional health, and lower body function.
RESULTS: In a multivariate analysis, continuous MMSE (b = 0.06; SE 0.02, p =.004) and Center for Epidemiological Studies-Depression (CES-D) (b = -0.53; SE 0.17, p =.002) scores at baseline were significantly associated with a summary performance measure of lower body function 2 years later, controlling for age, gender, marital status, education, selected medical conditions, and baseline summary performance score. A significant MMSE-by-CES-D interaction (p =.002) on summary performance score was also found after adjustments were made for age, gender, marital status, education, chronic health conditions, and baseline summary performance score. After adjusting for age, gender, marital status, education, selected medical conditions, and baseline summary performance score, subjects with low cognition (MMSE score 18-21) and high depressive symptoms (CES-D score > or = 16) were the most likely to have poor summary performance scores 2 years later (b = -0.95, SE 0.36, p =.008), followed by subjects with high cognition (MMSE score > 21) and high depressive symptoms (CES-D score > or = 16) (b = -0.57, SE 0.19, p =.003), and those with low cognition (MMSE score 18-21) and low depressive symptoms (CES-D score < 16) (b = -0.47, SE 0.22, p =.03), with high cognition (MMSE score > 21) and low depressive symptoms (CES-D score < 16) used as the reference.
CONCLUSIONS: Our results confirm prior investigations showing both cognitive function and emotional health predict subsequent lower body function, and extend these findings to older Mexican Americans. In addition, our results indicate that good emotional health moderates the impact of low cognition on subsequent physical function.