Epidemiology, Incidence and Mortality of Thyroid Cancer and their Relationship with the Human Development Index in the World: An Ecology Study in 2018

Objective: Thyroid cancer is one of the most common malignancies, with an incidence rate of about two fold in the last 25 years and accounting for 2% of all cancers. The Human Development Index (HDI) is used to measure the development of countries level. The aim of this study was to investigate thyroid cancer morbidity and mortality and its association with HDI. Methods: The present analysis is a descriptive cross-sectional study that is based on cancer incidence data and cancer mortality rates extracted from the World Bank for Cancer in 2018. The incidence and mortality rates and thyroid cancer distribution maps were drawn for world countries. To analyse data, correlation and regression tests were used to evaluate the correlation between incidence and mortality with HDI. The statistical analysis was carried out by Stata 14, and significance level was estimated at the level of 0.05. Results: The results showed a positive correlation between incidence and thyroid cancer (r = 0.497, P < 0.05); however, the correlation observed between mortality and HDI was negative, which was not statistically significant (r = 0.06, P > 0.05). There was a positive and significant correlation between incidence with gross national income per 1000 capita (r = 0.328, P < 0.0001), Mean years of schooling (r = 0.445, P < 0.0001) life expectancy at birth (r = 0.509, P < 0.0001) and expected years of schooling (r = 0.463, P < 0.0001); however, this correlation was not statistically significant in mortality rate (P 0.05). Linear regression model showed that increase in LEB (B = 0.2, confidence interval [CI] 95%: [0.01, 0.4]) significantly increased thyroid cancer incidence (P < 0.05). The regression analysis showed that increase in life expectancy at birth (B = 0.02, CI 95% [0.008, 0.04]) increased mortality (P < 0.05). The study showed that the mean incidence and thyroid cancer mortality in female were significantly higher than males (P < 0.05). Conclusion: The thyroid cancer incidence in high-HDI countries and the mortality rate in countries with low HDI are increasing. Therefore, HDI can be used to provide a clear picture for the distribution of this cancer in different parts of the world.