Investigating the incidence rate and geographical distribution of congenital hypothyroidism among neonates in Isfahan province using geographic information system (GIS) between 2002 and 2015.

Background Congenital hypothyroidism (CH) is one of the main causes of mental retardation in neonates. The disease is associated with genetic, climatic and environmental factors. Accordingly, the present study was conducted to determine the incidence rate and correlation of geographic factors with CH in Isfahan province in order to explain the role of climatic factors in the incidence of disease in this province. Methods This cross-sectional study was conducted to determine the incidence rate and geographical distribution of CH in neonates born in the Isfahan province from the beginning of 2002 to the end of 2015. To estimate the geographic distribution, the ArcGIS software (version 10.3) was used and to investigate the relationship between geographical factors and CH, the Poisson regression test and dispersion diagrams were used. Data analysis was done using the SPSS16 software. Results According to the results of the screening of 1,006,404 neonates born in Isfahan, the mean incidence rate of CH in all infants was 2.3, and that in male and female infants was 2.39 and 2.2 per 1000 live births, respectively. There was a statistically significant correlation between the city of residence (p = 0.01), climatic conditions (p = 0.044), annual precipitation (p = 0.027), sunlight (p = 0.01) and CH. However, there was no significant relationship between the mean altitude above sea level (p = 0.6), land use (p = 0.4) and relative humidity (p = 0.24). Conclusions Based on the findings of this study, the incidence rate of CH in Isfahan province was higher than the average of the country. Moreover, among the geographical factors, climatic conditions, annual precipitation and sunlight were associated with CH.