Age-dependent decline of association between obesity and coronary heart disease: a cohort study in a remote Australian Aboriginal community

OBJECTIVE To determine whether the association between obesity and coronary heart disease (CHD) in Aboriginal adults depends on age. DESIGN, SETTING AND PARTICIPANTS A cohort study with up to 20 years of follow-up of 849 participants aged 18-76 years in a remote Aboriginal community in the Northern Territory of Australia. MAIN OUTCOME MEASURES Newly diagnosed CHD cases were identified through hospital records according to ICD codes during the follow-up period. Cox proportional hazard model was used to assess whether the association between obesity and CHD depends on age. RESULTS During the follow-up period, 171 participants were diagnosed with CHD. On an average, the incidence rate of CHD increased with the increasing baseline BMI, 11.3%, 16.3% and 20.2% for normal weight, overweight and obese groups, respectively. HR of CHD for obesity were 2.6 (95% CI 1.1to 6.3), 1.2 (0.7 to 2.0) and 0.5 (0.1 to 2.1) for those <40, 40-59 and 60+ years, respectively. HRs corresponding to 1 SD increase in BMI were 1.4 (1.0 to 2.0), 1.2 (1.0 to 1.5) and 0.8 (0.5 to 1.2) for those <40, 40-59 and 60+ years, respectively. The interaction terms between age and BMI as category variables or as a continuous variable were statistically significant. CONCLUSIONS The association between obesity and CHD is stronger for younger adults than for older adults in Aboriginal Australians in the remote community. Our findings suggest that weight control efforts may produce more beneficial effects in CHD prevention in young adults than in older adults.