Diabetes and thyroid cancer mortality: a 12-year prospective follow-up of Taiwanese.

BACKGROUND: The association between diabetes and thyroid cancer is rarely studied. This study evaluated thyroid cancer mortality trend in Taiwanese population, mortality rate ratios between diabetic patients and general population, and risk factors in diabetic patients.

METHODS: In general population, age-standardized trends were evaluated from 1995 to 2006. A total of 113,347 diabetic men and 131,573 diabetic women aged ≥ 25 years recruited during 1995-1998 were followed to 2006. Age- and sex-specific mortality rate ratios were calculated and Cox's regression evaluated the risk factors.

RESULTS: A steady trend of thyroid cancer mortality was observed in the general population. A total of 20 diabetic men and 45 diabetic women died of thyroid cancer, with overall mortality rate 2.32 and 4.26 per 100,000 person-years, respectively. Mortality rate ratios showed positive association with magnitude increased with decreasing age: 1.85 (0.77, 4.43), 1.21 (0.54, 2.73), 2.53 (1.14, 5.59) and 5.80 (2.10, 16.01) for ≥ 75, 65-74, 55-64 and 25-54 years old, respectively, for men; and 0.78 (0.35, 1.74), 2.03 (1.31, 3.13), 2.99 (1.77, 5.04) and 5.34 (2.20, 13.00), respectively, for women. After adjustment, only age was significantly associated with thyroid cancer mortality. Sex, diabetes duration, diabetes type, body mass index, smoking, insulin use and area of residence were not significantly predictive for thyroid cancer mortality.

CONCLUSIONS: The annual thyroid cancer mortality during 1995-2006 in the Taiwanese general population has been steady. Our data suggest a higher risk in diabetic patients, with especially higher mortality rate ratios in younger age. Obesity, smoking and insulin use are not modifiable risk factor.