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 and factors associated with pterygium in Han and Mongolian adults at four survey sites in Inner Mongolia, China. Methods: A population-based, cross-sectional study was conducted. Using a stratified sampling method, we eventually included 2,651 participants of at least30 years of age from a total of 3,468 eligible residents. Factors associated with pterygium were analysed using univariate analysis and logistic regression models. Results: There were 1,910 Han adults and 741 Mongolian adults included in this study. The mean± standard deviation of age for individuals in the study cohort was 48.93±11.06 years. The overall prevalence of pterygium was 6.4% (n=169), and the prevalences of bilateral and unilateral pterygium were 1.4% (n=38) and 4.8% (n=128), respectively. The most common grade of pterygium was Grade 2. After univariate analysis, eleven factors were considered in a multivariate analysis. The results indicated that age (P<0.001), education level (P<0.001), outdoor occupation (P=0.026), and time spent in rural areas (P<0.001) were significantly associated with pterygium, whereas gender and ethnicity were not risk factors. In subgroup analysis, BMI≥28 was a protective factor for Han individuals (OR 0.42, 95% CI 0.21-0.81, P=0.01), but a risk factor for Mongolian individuals (OR 2.39, 95% CI 1.02-5.58, P=0.044). The BF% in Han and Mongolian individuals had significant difference (P<0.001). Conclusions: Our results indicated that an outdoor occupation, old age and time spent in rural areas are risk factors for pterygium in Inner Mongolia. Living near an urban survey site (Hohhot and Tsining District) and having a higher education level are protective factors for pterygium. Ethnicity, gender, smoking, diabetes and high blood pressure are not associated with pterygium. Different dietary structures in Han and Mongolian adults may lead to different fat content of body and therefore contributes to the prevalence of pterygium. Keywords: Pterygium, prevalence, Han and Mongolian, risk factors, protective factors