Body Mass Index versus Waist Circumference as Predictors of Disability Incidence in Mexican Aged 50 Years and Older

BACKGROUND: Higher body mass index (BMI) and waist circumference (WC) are associated with disability risk. However, of these two which measurement is a stronger predictor of disability in older Mexican adults is unclear.

OBJECTIVES: To investigate the association between BMI and WC on incidence of disability in Mexicans aged 50+ years.

METHODS: A secondary analysis was conducted on 2192 participants from prospective data of first (2001) and second wave (2003) of the Mexican Health and Aging Study. Measures included demographic, smoking status, medical conditions, activities of daily living (ADLs), BMI (Kg/m²), and WC (cm). The primary outcome variable of our study was ADL related disability. Logistic regression was used to examine the association between BMI and WC with disability among non-disabled participants at baseline.

RESULTS: At baseline, the mean BMI was 27.8 ± 4.9 and mean WC was 97.9 ± 12.3.  After adjusting for age and gender, high BMI (OR= 1.06, 95% CI=1.02-1.10) and high WC (OR=1.01, 95% CI=1.00-1.03) were both associated with high risk of 2-year incidence of ADL disability, when analyzed separately. When BMI and WC were examined simultaneously, high WC (OR=0.99, 95% CI=0.97-1.01) was no longer associated with higher risk of ADL disability while high BMI (OR=1.07, 95% CI=1.01-1.13) remained significantly associated with higher risk of ADL disability. Arthritis, diabetes and stroke were also significantly associated with ADL disability in both models.

CONCLUSION: High BMI is a stronger predictor of ADL disability in older Mexican adults. However, WC information could add a clinical significance. Thus both BMI and WC should be measured in longitudinal epidemiological studies.