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Body Mass Index and All-Cause Mortality Meta-Analysis
Study Questions:
What is the association between body mass index (BMI) and mortality across the world?
Methods:
This was an individual-participant data meta-analysis of prospective studies which reported BMI. Data from participants enrolled in 239 prospective studies conducted in Asia, Australia and New Zealand, Europe, and North America were used. Participants who were nonsmokers and had no pre-existing diseases were included. The first 5 years of follow-up were also excluded from the analysis. The primary analysis was all-cause mortality.
Results:
A total of 10,625,411 participants were included in the 239 studies (median follow-up 13.7 years), of which 951,455 participants in 189 studies were never-smokers and without chronic diseases at recruitment. Of the participants who survived 5 years, a total of 385,879 died during follow-up. Between a BMI of 20-25 kg/m2, the all-cause death was not significant (hazard ratio [HR], 1.00; 95% confidence interval [CI], 0.98-1.02 [for BMI 20-22.5 kg/m2] and HR, 1.00; 95% CI, 0.99-1.01 [for BMI 22.5 to <25 kg/m2]). The risk increased for lower BMI ranges including BMIs of 18.5 to <20.0 kg/m2 (HR, 1.13; 95% CI, 1.09-1.17), and BMIs of 15.0 to <18.5 (HR, 1.51; 95% CI, 1.43-1.59). For participants who were overweight, the risk of death increased with BMI (HR, 1.07; 95% CI, 1.07-1.08 [for BMI 25.0 to <27.5 kg/m2], and HR, 1.20; 95% CI, 1.18-1.22 [for BMI 27.5 to <30.0 kg/m2]). For obesity, the risk increased further. For grade 1 obesity (BMI 30.0 to <35.0 kg/m2), the risk was HR, 1.45; 95% CI, 1.41-1.48. For grade 2 obesity (BMI 35.0 to <40.0 kg/m2), the risk was HR, 1.94; 95% CI, 1.87-2.01, and for grade 3 obesity (BMI 40.0 to <60.0 kg/m2), the risk was HR, 2.76; 95% CI, 2.60-2.92. For BMIs >25.0 kg/m2, mortality increased approximately log-linearly with BMI. The hazard risk ratio per 5 kg/m2 units for higher BMIs was 1.39 (95% CI, 1.34-1.43) in Europe, 1.29 (95% CI, 1.26-1.32) in North America, 1.39 (95% CI, 1.34-1.44) in East Asia, and 1.31 (95% CI, 1.27-1.35) in Australia and New Zealand. The risk was greater in younger adults compared to older adults and greater in men compared to women.
Conclusions:
The investigators concluded that the associations of both overweight and obesity with higher all-cause mortality were broadly consistent in four continents. This finding supports strategies to combat the entire spectrum of excess adiposity in many populations.
Perspective:
These results suggest that increases in BMI are associated with increased risk for all-cause mortality across the world. Global measures to prevent overweight and obesity are warranted.
Keywords: Adiposity, Body Mass Index, Chronic Disease, Global Health, Metabolic Syndrome, Mortality, Obesity, Overweight, Primary Prevention, Risk
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