Obesity and the prevention of thyroid cancer: Impact of body mass index and weight change on developing thyroid cancer - Pooled results of 24 million cohorts

Background: Body weight may be a modifiable risk factor predisposing to different cancers. To establish a potential impact of weight change on thyroid cancer risk, we conducted a meta-analysis to evaluate the effect of body mass index (BMI) and weight change over time as a risk of developing thyroid cancer (TC). Methods: A systematic search was performed up to February 25, 2020. Pooled relative risk (RR) were estimated using fixed and random models. Heterogeneity between articles was examined using Q-test and I-2 index. Evaluation of publication bias was conducted with Egger's regression test. Results: A total of 31 studies including 24,489,477 cohorts were eligible. Pooled analysis revealed that normal and underweight cohorts were associated with a decreased risk of TC (RR = 0.68, 95%CI = 0.65-0.71,p < 0.001) and (RR = 0.92, 95%CI = 0.91-0.93, p < 0.001), respectively. In contrast, overweight and obese cohorts were more likely to develop TC (RR = 1.26, 95%CI = 1.24-1.28, p < 0.001 and RR = 1.50, 95%CI = 1.45-1.55, p < 0.001, respectively). Obesity was associated with higher risk of developing TC among women (RR = 1.29, 95% CI = 1.14-1.46, p < 0.001), but not men (RR = 1.25, 95%CI = 0.97-1.62, p = 0.08). Furthermore, weight gain increased the risk of developing TC (RR = 1.18, 95%CI = 1.14-1.22, p < 0.001), while weight loss decreased the risk (RR = 0.89, 95%CI = 0.85-0.93, p < 0.001). Results showed similar trends of weight change effect in both males and females. Conclusions: Obesity is associated with higher risk of developing TC in women. However, maintaining a healthy weight is associated with reduced risk of TC in both women and men. Shifting our practice to include weight control strategies will help lead to cancer prevention.

Automated summary

The meta-analysis found that normal and lower body weight were associated with a decreased risk of thyroid cancer, while overweight and obese individuals had an increased risk. Obesity was linked to higher risk in women, with weight loss decreasing the risk and weight gain increasing it. Maintaining a healthy weight was shown to reduce the risk of thyroid cancer in both men and women.