Obesity and Mortality in a Prospective Study of a Middle-Aged Industrial Population

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Abstract
Although obesity is an established risk factor for coronary heart disease and stroke mortality, its role as a risk factor for other causes of death has not been extensively investigated, particularly in an industrial population. This prospective mortality study included 20 years of follow up of middle-aged industrial workers (n = 7139) at Shell Oil Company's manufacturing and research facilities. Baseline health risk factor data as of December 31, 1983, and mortality data as of December 31, 2003, were extracted from the company's Health Surveillance System. Relative risks (RRs) for selected causes of death by body mass index (BMI) category were calculated using the Cox proportional hazards model adjusted for age, sex, and smoking status as well as other potential risk factors, ie, cholesterol, hypertension, and fasting blood glucose. Compared with employees with BMI between 18.5 and 24.9 kg/m2, those with BMI of 30 kg/m2 or greater had a statistically increased RR (adjusted for age, sex, and smoking status) for all causes (RR, 1.25; 95% confidence interval [CI] = 1.03–1.51), coronary heart diseases (RR, 2.29; 95% CI = 1.50–3.50), cardiovascular diseases (RR, 2.22; 95% CI = 1.51–3.27), diabetes (RR, 16.97; 95% CI = 2.11–136.44), and accidental deaths (RR, 2.64; 95% CI = 1.23–5.66). After adjusting for additional covariates, coronary heart diseases and cardiovascular diseases remained statistically significant. Obesity was associated with increased death rates for all causes, cardiovascular diseases, diabetes, and all accidents. Overweight individuals had a statistically lower cancer rate. Death rates for lung cancer and respiratory disease were lower among overweight/obese employees but did not reach statistical significance. Reductions of employee obesity can be an effective means of reducing these causes of death.