Risk of thyroid cancer in relation to height, weight, and body mass index in Japanese individuals: a population‐based cohort study

Greater height and body mass index (BMI) have been associated with an increased risk of thyroid cancer incidence in Western countries. However, few epidemiological studies have assessed the association between anthropometric factors, such as BMI, height, or weight, and thyroid cancer incidence in Asian populations. Using the population‐based Japan Public Health Center‐based prospective study database, we investigated the relationship between anthropometric factors and thyroid cancer incidence. Data on anthropometric factors were collected through a self‐administered questionnaire at baseline. The hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using the Cox proportional hazards model, and the exposure level was categorized into quintiles. A total of 49,062 men and 53,661 women enrolled between 1990 and 1994 were included in our analyses, and 191 cases (37 in men and 154 in women) of thyroid cancer were identified, with 1,695,702 person‐years of follow‐up until 2010. Compared with the male group with height ≤160 cm, HRs of the male groups with height 165–168 cm and ≥169 cm were 3.92 (95% CI; 1.33–11.55, P = 0.013) and 4.24 (95% CI; 1.32–13.61, P = 0.015), respectively, and the HR per 5‐cm increase in height was 1.12 (95% CI 1.06–1.18, P < 0.001). In contrast, the association between anthropometric features and the risk of thyroid cancer did not significantly differ among women. In this population, an increase in risk for increased height was observed in men, but no associations between anthropometric indexes and thyroid cancer risk were observed in women.