Attributable risk fraction of four lifestyle risk factors of thyroid cancer: a meta-analysis

Background Lifestyle risk factors such as obesity, overweight, smoking and radiation exposure related to thyroid cancer. This study estimated the amount of excess risk that attributed to risk factors. Methods Major electronic databases were searched until February 2016. Epidemiological studies addressing the association between lifestyle risk factors and thyroid cancer were enrolled. The results were expressed as ARF with 95% confidence intervals (CIs) using a random-effects-model. Results We identified a total of 13 321 references and included 17 studies. The excess risk of thyroid cancer attributable to radiation exposure was 14% (95% CI: 5%, 23%; eight studies, I-2 = 88.7%), to obesity was 13% (95% CI: 5%, 21%; four studies, I-2 = 68.7%), to overweight was 10% (95% CI: 2%, 17%; four studies, I-2 = 4.1%) and to smoking was -13% (95% CI: -33%, 6%; five studies, I-2 = 30.6%). So obesity, overweight and radiation exposure are significantly associated with increased thyroid cancer risk and smoking has a protective effect on thyroid cancer but not significant. Conclusion A significant amount of the incidence of thyroid cancer is attributable to lifestyle risk factors. Since these factors are entirely preventable, so it is necessary to reduce factors that are associated with increased thyroid cancer risk and proper education to the community. Thus weight loss and protection against radiation can effectively reduce the incidence rate of thyroid cancer but smoking can have a protective effect.