Trends and cross-country inequalities in the global burden of thyroid cancer, 1990-2021: A population-based study.

BACKGROUND: To evaluate the trends in the burden of thyroid cancer (TC) over the past 30 years, assess inequalities between countries, and predict changes by 2045. METHODS: TC incidence, prevalence, deaths, and disability-adjusted life years (DALYs), with 95% uncertainty intervals (UIs), were obtained from the Global Burden of Diseases, Injuries, and Risk Factors Study 2021. We analyzed global, regional, and national trends during 1990-2021. Decomposition analysis assessed population growth, aging, and epidemiological change. Health inequalities were quantified using World Health Organization-recommended methods, and burden was projected to 2045. RESULTS: In 2021, estimates were 249,538 (95% UI: 223,290-274,638) incident cases, 1,987,148 (1,776,275-2,198,245) prevalent cases, 44,799 (39,925-48,541) deaths, and 1,246,485 (1,094,416-1,375,853) DALYs globally. East Asia had the most cases, whereas high-income North America had the highest age-standardized rate (ASR). During 1990 to 2021, TC burden increased, with incidence, prevalence, and deaths rising fastest during 2000 to 2010. Females (53.51%) and middle-Socio-demographic Index (SDI) regions (41.69%) accounted for the largest DALY proportions. DALY changes were driven mainly by population growth, followed by aging. SDI-related inequalities increased: the incidence gap between the highest- and lowest-SDI countries rose from 2.63 (95% confidence interval: 2.28-2.98) in 1990 to 4.58 (4.04-5.13) in 2021, and the prevalence gap from 20.17 (17.31-23.02) to 36.96 (32.26-41.65). During 2020-2045, incidence and prevalence numbers and ASRs are projected to increase annually. Although death ASRs are expected to decline, death counts will rise. In 2045, incident cases, prevalent cases, and deaths are projected to reach 449,910 (95% UI: 45,706-884,520), 3,295,386 (310,305-6,488,732), and 78,818 (27,472-130,171), respectively. CONCLUSIONS: Global TC burden increased during 1990-2021, mainly because of population growth and aging. High-SDI countries bear a disproportionate burden, and inequalities have widened. Rising cases and unequal distribution challenge TC control and management. These findings may inform public health policy and equitable resource allocation.