Self-Reported Physical Inactivity and Waist Circumference Independently Predict All-Cause Mortality in U.S. Adults

Abstract

Background: Physical inactivity (PIA) is a major risk factor linked to many chronic diseases as well as premature mortality. Waist circumference (WC) is a measure of abdominal obesity and is also associated with many health problems. The purpose of this study was to examine both PIA and WC as predictors of all-cause mortality in adults. Methods: Data for this research came from the 2001-02 National Health and Nutrition Examination Survey (NHANES) and linked mortality file. Only participants who were 18+ years of age and eligible for mortality linkage were used in the analysis. PIA status was determined from the answers to two questions that asked subjects if they participated in moderate and then vigorous physical activity. WC was assessed by a trained health professional. Cox proportional hazards regression was used to model the effects of PIA and WC on mortality while controlling for age, sex, race, and income. Results: Approximately 33% (SE=1.12) of adults were physically inactive at interview date with mean WC of 95.6 (SE=0.21) centimeters (cm). A total of 55,288 person-years of follow-up was observed with 965 deaths. In the unadjusted model, physically inactive adults were at greater risk of mortality (Hazard Ratio (HR) =2.42, 95% CI: 2.006, 2.928) as compared to their more active counterparts. A 2% increase in mortality (HR=1.02, 95% CI: 1.016, 1.025) was seen for each 1-cm increase in WC. The fully adjusted model showed a significant increase in mortality (HR=1.40, 95% CI: 1.130, 1.727) among those who were physically inactive independent of a 1% increase in mortality (HR=1.01, 95% CI: 1.002, 1.016) for each 1-cm increase in WC. Conclusion: Results from this study indicate that PIA and WC are independent predictors of mortality in adults. Health promotion programs should consider both physical activity as well as abdominal obesity in their programming objectives.