The association of gastrointestinal cancers (esophagus, stomach, and colon) with solar ultraviolet radiation in Iran—an ecological study
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Iran has variations in the incidence of cancer in its different provinces. Moreover, it is one of the countries with a high incidence of gastrointestinal cancers in the world. The aim of this study was to investigate the relation between the incidence of esophageal, stomach, and colon cancers with ultraviolet radiation. This is an ecological study. The age-standardized incidence of cancer from 2004 to 2008 was obtained from the National Cancer Registry of Iran for all provinces. UV index data was taken from the world weather site. The altitude and latitude of cities were obtained from the National Topography Organization. Demographic variables were taken from the STEPS report of the Ministry of Health. In this study, lung cancer were used as the index of the effects of smoking. Data were analyzed using the SPSS22 software and through linear regression. UV emission levels showed a strong negative correlation with the incidence of esophageal and gastric cancers, in both genders, in all years. However, this correlation was stronger in men. UV radiation showed a significant correlation with colon cancer among both genders as well. There was no relation between altitude and incidence of cancer. Linear regression results showed that with a unit increase in UV, the incidence of gastric and esophagus cancers in males decreases by β = −4.99 and β = − 3.16 significant coefficients, respectively. Cities with higher levels of UV index have a relatively lower incidence of gastrointestinal cancers. Ultraviolet radiation may act as a protective factor against these cancers.
KeywordsCancer UVB Latitude Ecological study Iran
The authors wish to thank the Neurology Research Center, Kerman University of Medical Sciences, for the sincere cooperation.
NK supervised this study, wrote the proposal, edited the draft, EN did the statistical analysis, wrote the initial draft, and collected data. MRG gave scientific advice and edited the draft. MEM helped in collecting data and doing searches. All the authors read, commented, and approved the final article.
This study was financially supported by Kerman University of Medical Sciences.
Compliance with ethical standards
This study was approved by the Ethics Committee of Kerman University of Medical Sciences, Ethics Code: IR.KMU.REC.1396.2395.
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