Fast track — ArticlesBody-mass index and cancer mortality in the Asia-Pacific Cohort Studies Collaboration: pooled analyses of 424 519 participants
Introduction
More than 1 billion people worldwide are overweight or obese, conditions that are a main risk factor for chronic diseases, including some cancers.1 Because of its widespread prevalence and effect on many health conditions, excess weight is ranked as the seventh most important contributor to mortality worldwide.2 As in the west, many Asian countries such as China, South Korea, Thailand, and Singapore are experiencing a steep rise in the prevalence of obesity in their populations,3 although compared with the west, the prevalence remains low.3, 4
Excess weight and obesity are associated with increased risk of several site-specific cancers, with a 5 kg/m2 higher body-mass index (BMI) typically associated with risk ratios in the range of 1·10–1·60.5 The evidence linking excess weight and obesity to cancer has mainly come from Western populations, with few data from Asians,6, 7, 8 in whom adiposity can be substantially greater for the same BMI.9, 10 Furthermore, the background prevalence of other dietary and lifestyle risk factors for cancer might also differ between Western and Asian populations,11 which could affect the association between excess weight and subsequent cancer risk. Recent meta-analyses of Asian data, mainly from Japan or Hawaii, show that higher BMI is associated with increased risks of cancer of the female breast5 and colorectum12 in populations from Asia or the Asia-Pacific region, compared with North America, Europe, and Australia.
The present study, which uses data from the Asia-Pacific Cohort Studies Collaboration (APCSC), has two aims: to examine associations between BMI and site-specific cancer mortality in populations of the Asia-Pacific region, and to assess whether the magnitude and direction of the associations are consistent between geographic populations in Asia and outside Asia (Australia and New Zealand) which, to the best of our knowledge, has not been previously systematically examined using individual participant data.
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Procedures
The APCSC is a large, collaborative, data-pooling project involving data from more than 600 000 participants in the Asia-Pacific region. Details of the collaboration have been described elsewhere.13, 14 Briefly, studies were eligible for inclusion if they had the following criteria: a study population from the Asia-Pacific region; a prospective cohort study design; at least 5000 person-years of follow-up; date of birth (or age), sex, and blood pressure recorded at baseline; date of death or age
Results
Individual participant data were included from 39 cohorts (webtable 2), consisting of 424 519 people, of whom 326 387 (77%) were from Asian cohorts and 175 364 (41%) were female; mean age was 48 years; and median year of recruitment was 1992 in cohorts from Asia and ANZ. Comparing baseline characteristics with the Asian cohorts, individuals from ANZ had higher BMI (mean 26·6 kg/m2 [SD 3·7] in men and 26·0 kg/m2 [4·9] in women vs 23·0 kg/m2 [2·7] in men and 22·6 kg/m2 [3·1] in women from Asia);
Discussion
In the present study, based on data from more than 400 000 individuals from 39 prospective cohort studies in the Asia-Pacific region, we found that among individuals with a BMI higher than 18·5 kg/m2, there was a positive and continuous association between BMI and all-cancer mortality, such that a 5 kg/m2 increase in BMI was associated with a relative risk (HR) of 1·09 (95% CI 1·04–1·14), after excluding cases of lung and UADT cancer, which had a negative association with BMI. Compared with
Glossary
- Left censoring
- Exclusion of study participants with follow-up time less than a certain duration
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