Associations of intensity, duration, cumulative dose, and age at start of smoking, with thyroid cancer in Chinese males: A hospital-based case–control study in Zhejiang Province

Introduction There has been considerable research on the association between smoking status and thyroid cancer risk in males, yet the findings are inconsistent. In this study, we investigated the associations of intensity, duration, cumulative dose, and age at start of smoking, with thyroid cancer in Chinese males. Methods From a 1:1 matched case–control study conducted between 2015 and 2017 in Zhejiang Province, China, 676 pairs of male subjects were included in the analysis. The associations between smoking characteristics and thyroid cancer were evaluated in logistic regression models by odds ratios (ORs) with 95% confidence intervals (CIs). Results Compared with never smokers, the former smokers were 0.096 times (95% CI: 0.012–0.778) less likely to have thyroid cancer. The significant inverse association was not observed in current smokers (OR=0.333; 95% CI: 0.084– 1.322). Among both former and current smokers, higher smoking intensity (>10 cigarettes/day), duration (>15 years), and cumulative dose of smoking (>10 packyears) were significantly associated with reduced occurrence of thyroid cancer. Conclusions Our findings indicate that former smoking is inversely associated with thyroid cancer occurrence in Chinese males. The reduction in the occurrence of thyroid cancer was also confirmed for both former and current smokers with higher smoking intensity, duration, and cumulative dose.