# Impact of Urbanization and Sunlight Exposure on Cataract Incidence
## 5 Conclusions  
Compared to other similar studies with small sample sizes, the most significant advantage of our research is that we used the Taiwan NHI claim database (LHID2010), including a 1,000,000 insured cohort for 10 years, which well-represented the population of 23.5 million in Taiwan,  
Our study concludes that, after controlling some essential confounding variables, such as demographics (age, gender, occupation) and comorbidities (such as diabetes, hypertension, chronic kidney disease), a higher degree of urbanization and more prolonged sunlight exposure significantly impact developing senile cataracts. Therefore, unlike some other studies' results, the results from our study did not support the negative association between urbanization and the development of cataracts.  
Previous studies have confirmed that the urban landscape's natural settings, such as green spaces and vegetation, positively affect health [22; 23]. The major limitation of our study was the lack of some spatial or ecological variables, such as environmental greenness, in the analytical model. We suggest that future researchers adopt Geospatial Information Technology and use the Normalized Difference Vegetation Index to measure the environmental greenness and include it in the analysis. Suppose future studies prove that environmental greenness is a profound factor of urbanization related to cataract development; in that case, we can suggest that the government adopt policies to enhance the city's afforestation and improve people's health.  
According to previous studies, sufficient intake of Vitamin C, Lutein/Zeaxanthin, B vitamins, Omega-3 fatty acids, multivitamins, etc., can decrease the risk of developingcataracts [24; 25]. Therefore, the absence of participants' nutritional status is the second limitation of this study. If possible, we suggest that future studies include participants' nutritional status as a confounder in the analysis.  
Additionally, our study also demonstrates the importance of protecting people's eyes from direct sunlight exposure, especially for those who have to work under sunlight for an extended period, to prevent the development of senile cataracts. Therefore, the government should also provide health education and promote healthy behavior, such as wearing sunglasses or a hat under the sunlight to improve eye health.  
Conceptualization, W.-S.Y. and N.-W.K.; data curation, C.-H.W.; formal analysis, W.-S.Y. and C.-H.W.; methodology, N.-W.K. and W.-S.Y.; writing--original draft, C.-H.W.; writing--review & editing, N.-W.K. and C.-H.W. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
This study was confirmed Exemption by TMU-Joint Institutional Review Board in meeting #108-09-04 (date: 26 September 2019; TMU-JIRB N201909005).  
This study used the administrative database for analysis, so the informed consent was not required.  
The National Health Insurance Research Database, which has been transferred to the Health and Welfare Data Science Center (HWDC). Interested researchers can otain the data through formal application to the HWDC, Department of Statistics, Ministry of Health and Welfare, Taiwan ([[https://dep.mohw.gov.tw/docs/cp-5119-59201-113.html](https://dep.mohw.gov.tw/docs/cp-5119-59201-113.html)]([https://dep.mohw.gov.tw/docs/cp-5119-59201-113.html](https://dep.mohw.gov.tw/docs/cp-5119-59201-113.html)), accessed on 2 September 2021).  
The authors declare no conflict of interest.