Geographical variation in attributable fraction of overweight and obesity on cancer incidence in Taiwan

Background: Excess body weight, expressed as increased body-mass index (BMI), have been linked to development of cancer in previous studies. As a modifiable lifestyle risk factor, body weight control has the potential to reduce the risk of several major cancer sites. To provide inform to policymakers for national cancer control, we aimed to estimate the number of incident cases of various cancers attributable to overweight and obesity in Taiwan and to compare the results by geographic areas.

Methods: By using specific risk estimates from a published meta-analysis and age- and gender-specific mean BMI distribution from a national survey (NHIS2005), we calculated age- and gender-specific population attributable fractions (PAFs) for specific cancer sites. National and geographical cancer incidence in 2011 were obtained from Taiwan Cancer Registry (TCR). Monte Carlo simulation was applied for 95% confidence intervals (CI) estimation. A geography information system (GIS) tool was used to observe the patterns of four geographical areas in Taiwan (Northern, Central, Southern, and Eastern areas).

Results: In 2011, an estimated 2.8% (95% CI: 2.2–3.4%; 1,132 cases) of incident cancer cases among men were attributable to overweight and obesity in Taiwan. The corresponding number was slightly higher among women (3.1%; 95% CI: 2.4–3.9%; 1,628 cases). In men, overweight and obesity mainly contributed to colon and rectum cancer cases (799 cases), while in women, breast and endometrial cancer showed highest number of cancer cases (951 cases) related to overweight and obesity. In subnational analysis, we found a higher PAF for overweight and obesity for associated cancer incidence in Eastern area (11.7%) than the other areas (6.9%~7.4%) among Taiwanese woman. In contrast, men in Eastern area showed the lowest proportion of associated cancer incidence than other areas (6.5% vs. 8.4%~8.5%).

Conclusion: A targeting prevention strategy to modify overweight and obesity would substantially decrease the cancer burden in Taiwan, especially colorectal cancer for men and breast and endometrial cancer for women. Geographical patterns of excess body weight and cancer incidence provided further implications for health policies and programs and for health equity.