Cognitive status and incident disability in older Mexican Americans: findings from the Hispanic established population for the epidemiological study of the elderly.
OBJECTIVE
To determine the effects of baseline cognitive function on incidence of disability in activities of daily living (ADL) in initially non-disabled Mexican-American elderly over a 7-year period.


METHODS
A prospective cohort study.


METHODS
Southwestern United States: Texas, California, Arizona, New Mexico, and Colorado.


METHODS
A population-based sample of Mexican Americans aged 65 and over who completed the Mini-Mental State Examination (MMSE) and other relevant variables at baseline. The sample at baseline consisted of 2731 subjects, of which 2431 were non-ADL disabled.


METHODS
In-home interviews in 1993-94, 1995-96, 1998-99, and 2000-2001 assessed sociodemographic variables, selected medical conditions (stroke, cancer, diabetes, arthritis, and hip fracture), cognitive function, depressive symptomatology, and ADLs.


RESULTS
In a Cox proportional regression analysis, a significant relationship was evident between MMSE score at baseline and risk of incident ADL disability over a 7-year period. Among non-disabled subjects at baseline, the hazard ratio of any new ADL limitation was 1.58 (95% CI, 1.18-2.12) for those with impaired cognition (MMSE score 0-21), 1.38 (95% CI, 1.04-1.82) for low normal cognition (MMSE score 22-24), and 1.30 (95% CI, 1.02-1.66) for normal cognition (MMSE score 25-28) when compared to subjects with high-normal cognition (MMSE score 29-30), adjusting for sociodemographic variables, presence of selected medical conditions and depressive symptoms at baseline. Similar results were also found when MMSE score was used as a continuous variable. Among non-disabled subjects at baseline, each unit increase in MMSE score decreased the risk of onset of any ADL limitation over a 7-year follow-up period, controlling for relevant variables at baseline (HR=0.97; 95% CI, 0.95-0.99).


CONCLUSIONS
Low MMSE score was associated with increased risk for incident ADL disability over a 7-year period in older Mexican Americans. Given the social, economic, and health impact of cognitive impairment, these findings suggest a need to develop effective intervention programs that delay or prevent the onset of cognitive and ADL disability in the elderly.
Raji
Mukaila A
MA
Department of Internal Medicine, Center on Aging, University of Texas Medical Branch, Galveston, Texas 77555-0460, USA. muraji@utmb.edu
Al Snih
Soham
S
Ray
Laura A
LA
Patel
Kushang V
KV
Markides
Kyriakos S
KS
D000203:Activities of Daily Living; D000368:Aged; D003072:Cognition Disorders / Q000208:ethnology* / Q000523:psychology; D015331:Cohort Studies; D006233:Persons with Disabilities / Q000523:psychology*; D005260:Female; D015577:Geriatric Assessment; D006305:Health Status Indicators; D006801:Humans; D015994:Incidence; D007407:Interviews as Topic; D008297:Male; D008609:Mental Status Schedule; D017058:Mexican Americans / Q000523:psychology*; D016016:Proportional Hazards Models; D011446:Prospective Studies; D015206:Southwestern United States / Q000453:epidemiology