Objectives: French Polynesia has one of the world's highest thyroid cancer incidence rates. A case-control study among native residents of French Polynesia included 219 cases of differentiated thyroid cancers diagnosed between 1979 and 2004 (195 women/24 men) matched with 359 population controls (315 women/44 men) on the date of birth.
Methods: Anthropometric factors were analyzed by conditional logistic regression.
Results: The risk of thyroid cancer for women in the highest quartile of body mass index (BMI) before diagnosis and at age 18 was 2.3-fold higher (95% CI, 1.1-4.7 p = 0.04) and 2.3-fold higher (95% CI, 1.2-4.4 p < 0.01), respectively, compared with the lowest. Women who were overweight (BMI = 25-29.9 kg/m2) or obese (BMI > or = 30 kg/m2) at age 18 and before diagnosis had an increased risk compared with those with a normal lifelong weight (OR = 6.2; 95% CI, 2.5-15.5 p < 0.01). Results for excess weight appeared in similar directions for men, although the number of cases was too small to provide reliable estimates. Height was positively associated with thyroid cancer among men and women.
Conclusion: This study shows the role of excess body weight, especially if the onset is during early adulthood, and elevated height in the risk of differentiated thyroid cancer in populations born in French Polynesia.