Thyroid carcinoma incidence and mortality analysis during 1981–2001 in Tianjin, China

Abstract

To describe the long-term incidence and mortality trends of thyroid carcinoma and relate them to potential risk factors. All of the cases were from The Tianjin Cancer Registry. Numbers in each age-sex specific population for the six urban districts were obtained from the Tianjin Police Head Office. Descriptive epidemiological methods were used to study the incidence rates of thyroid cancer. Age-sex specific incidence rates were calculated and plotted. The incidence and mortality rate was compared from 1981 to 2001 using the χ 2 trend test. The average incidence rate and mortality was compared using the χ 2 test. Age at diagnosis was compared with t-test. All statistical analyses were carried out using SAS 8.1 for windows. A total of 1,318 cases from thyroid cancer were identified in Tianjin between 1981 and 2001, 352 males and 966 females respectively. The incidence rates have increased from 0.87/100,000 in 1981 to 2.54/100,000 in 2001, up 193%. Females had consistently higher incidence rates than males across all age groups during this period ( χ 2 = 294.429, p < 0.001). While the observed incidence increases were significant in both males and females, the magnitude of incidence increase was greater in females with the incidence ratios between males and females changing from 1:2.7 in 1981 to 1:4.6 in 2001. The results also suggest age-gender interactions. Male incidence rates increased gradually with increasing age and peeked around 60 years of age. However, the incidence rates in females climbed steeply after age 25 and reached its highest in the 35∼50 ages. The average mortality rate was 0.37/100,000. The mortality rates were also found to be higher in older age groups in both females and males. Although the incidence trend increased with time, the mortality trend changed a little. The significant increase in thyroid carcinoma incidence during the last 21 years reported in this study suggests that changes in environmental factors may have played an important role. Further epidemiological investigations are warranted.