# Correlation Between Sunlight Exposure Time and Cataract Prevalence in Korean Adults
## 4 Discussion
Various previous research results related to the level of education on cataracts show that a lower education level is associated with cortical cataracts and nuclear cataracts. Educational status may have a dependent relationship with socioeconomic status. However, it has actually been shown to be an independent risk factor for cataracts [34; 35]. These authors also reported that socioeconomic status and educational status may present the possibility of more risk factors associated with common lifestyles that may create risk factors that have not yet been explained [34; 35]. The results of our study's analysis of differences in cataract incidence according to the sunlight exposure and education level showed that the incidence of cataracts was higher in university graduates than in elementary-school graduates when exposed to sunlight for 2 to 5 h. In the 5 h or more group, it was confirmed that elementary-school graduates had a higher incidence of cataracts than university graduates. This means that in Korea, the higher the level of education, the more people work indoors, and the less time they are exposed to sunlight. However, the lower the level of education, the more work is performed outdoors than indoors. It is inferred that these workers will be more affected by sunlight exposure. In addition, as a result of analyzing the difference in cataract incidence according to the sunlight exposure and place of residence, the cataract incidence rate was significantly higher in large cities such as Seoul and Busan in the 2-5 h group, and the incidence rate was significantly higher in rural areas such as Gangwon-do and Gyeongbuk in the 5 h or more group. It was very high. Therefore, it was confirmed that the prevalence of cataracts was higher in large cities despite shorter sunlight exposure times than in rural areas. This allows for a meaningful comparison of 4 out of 16 regions in Korea. It was confirmed that the prevalence of cataracts was higher even with shorter sunlight in highly urbanized areas among large cities than in two rural areas with very low urbanization among rural areas. Meanwhile, a study in Taiwan reported that participants living in highly urbanized areas had a higher prevalence of senile cataracts than those living in other levels of urbanization [36; 37]. However, another study reported that the prevalence of cataracts was higher in rural areas than in urban areas in southern India, and that people living in rural areas were more likely to develop cataracts [38]. Through this study, it was confirmed that Koreans had a higher incidence of cataracts when exposed to sunlight for more than 5 h. In addition, when analyzing the prevalence of cataracts according to the sunlight exposure time by sociodemographic characteristics, different differences were found between cases where the sunlight exposure time was 2 to 5 h and cases where it was more than 5 h.  
As a result of the analysis of factors affecting the prevalence of cataracts according to the sunlight exposure time, women had a high incidence of cataracts for 2 to 5 h of sunlight exposure, and men had a high incidence of cataracts for more than 5 h of sunlight exposure. In addition, age-related differences were significantly higher after age 45 in both the 2 to 5 h sunlight exposure group and the 5 h sunlight exposure group. The difference in education level-related cataract prevalence was higher in university graduates in the 2 to 5 h sunlight exposure group, and higher in elementary-school graduates in the 5 h sunlight exposure group. And in terms of regional differences, the incidence of cataracts was high in large cities for 2 to 5 h of sunlight exposure, and the incidence of cataracts was high in rural areas for more than 5 h of sunlight exposure. This means that people in urban areas are less likely to be exposed to sunlight because they spend a lot of time indoors, while those in rural areas outside the city are more likely to be exposed to sunlight than urban areas because there is a lot of outdoor activity.