Long-term consequences of body mass index for cardiovascular mortality: The Chicago heart association detection project in industry study

PURPOSE: This report: 1) examines the importance of long-term follow-up (25 years) in BMI-cardiovascular mortality associations in eight age-gender subcohorts from the Chicago Heart Association Detection Project in Industry; and 2) addresses the impact of previously identified methodologic problems in studies on weight-mortality associations, which include no adjustment for cigarette smoking, adjustment for physiological effects of obesity, and no exclusion of early deaths. METHODS: Associations were adjusted for age and ethnicity only, then for cigarettes/day, and for systolic blood pressure, serum cholesterol, and diabetes, for three periods of follow-up, 0 to 15, 6 to 15, and 16 to 25 years. RESULTS: In 25-year follow-up with exclusion of deaths for 0 to 15 years, there was a positive association in all subcohorts, with seven significant, both with and without adjustment for smoking or obesity-related risk factors. In contrast, with adjustment for obesity-related risk factors and no exclusion of early deaths in shorter-term (15-year) follow-up, there were two non-significant positive, three non-significant inverse, one significant positive, and one significant quadratic association. CONCLUSION: Failure to address potential methodologic problems can substantially alter associations in BMI-mortality studies and may contribute to observed differences among studies. The long-term outlook with overweight or obesity is adverse and deserves concerted efforts in prevention and treatment.