Body mass index and waist circumference as predictors of all-cause mortality in an Aboriginal Australian community

Objective Although elevated body mass index (BMI) and waist circumference (WC) have been identified as risk factors for mortality, data from the Australian Aboriginal communities are scarce. This study examined the associations of BMI and WC with all-cause mortality in an Australian Aboriginal community. Methods A total of 934 Aboriginal adults, aged 18–76 years, who participated in a community-wide screening programme in Australia's Northern Territory from 1992 to 1998, were followed-up prospectively for up to 18 years for death outcomes. The hazard ratios for mortality were estimated by baseline BMI and WC. Age, sex, smoking and alcohol consumption status were adjusted for in multivariable analysis. Results In 14,750 person-years of follow-up, 216 deaths were recorded. For each standard deviation increase in BMI, the risk of all-cause death decreased by 9% (95% CI: 0.80–1.05); whereas for each SD increase in WC, the risk of all-cause mortality increased by 17% (95% CI: 1.03–1.33). The risk of mortality was lower in the 3rd BMI tertile compared to the 1st tertile for mortality after adjusting for WC, age, sex, smoking and alcohol consumption. Risk of death was higher in WC tertile 3 compared to tertile 1 after adjusting for BMI, age, sex, smoking and alcohol consumption. Conclusions The risk of all-cause mortality among participants increased with higher WC, while participants with relatively higher BMI had a lower mortality risk. WC had stronger association with mortality than did BMI. The results indicate the importance of assessing WC measures in studies conducted in Aboriginal Australia