Prevalence and associated factors for Pterygium in Han and Mongolian adults: across-sectional study in inner Mongolian, China

Abstract Background: To investigate the prevalence of pterygium and associated factors in Han and Mongolian adults at four survey sites in Inner Mongolia, China.Methods: We conducted a population-based, cross-sectional study as part of the China National Health Survey (CNHS). By means of a stratified sampling method, we finally included 2,651 participants of 30 years of age or older from a total of 3,468 eligible residents. Factors associated with pterygium were analysed by a univariate analysis and logistic regression models.Results: The study population included 1,910 Han and 741 Mongolian adults. The mean age±standard deviation of the study cohort was 48.93±11.06 years. The overall prevalence of pterygium was 6.4% (n=169); 1.4% (n=38) of the cases were bilateral and 4.8% (n=128) were unilateral. The most common grade of pterygium was Grade 2. Based on the results of the univariate analysis, eleven factors were included in a multivariate analysis. The results indicated that age (P<0.001), outdoor occupation (P=0.026), and time spent in rural areas (P<0.001) were significantly associated with pterygium. Sex and ethnicity were not identified as risk factors.Conclusions: Our results indicated that outdoor occupation, old age and more time spent in rural areas were risk factors for pterygium in Inner Mongolia. At the same time, town as a survey site (Hohhot and Tsining District) was a protective factor for pterygium. Ethnicity, gender, smoking, diabetes and high blood pressure are not associated with pterygium.Trial registration KEYWORDS: pterygium, prevalence, Han and Mongolian, risk factors, protective factors