Prevalence of and risk factors for refractive error: a cross-sectional study in Han and Mongolian adults aged 40–80 years in Inner Mongolia, China

Abstract

Objectives To assess the prevalence of and risk factors for refractive error (RE) in Han and Mongolian adults aged 40-80 years in Inner Mongolia in China and to identify ethnic differences in RE between these populations. Methods Our cross-sectional study is part of the China National Health Survey (CNHS). The age-adjusted prevalence of RE in Han and Mongolian adults aged 40-80 in Inner Mongolia were compared. A multivariable logistic regression model was used to identify risk factors. Results Among 2090 people, the age-adjusted prevalence of myopia (SE < −0.5D), hyperopia (SE > 0.5D), high myopia (SE < −6.0D) and astigmatism (cylinder ≥ 0.5D) were 29.4% (95% confidence interval (CI), 27.4-31.3%), 28.4% (95% CI, 26.4-30.5%), 3.6% (95% CI, 2.8-4.4%) and 65.9% (95% CI, 63.9-67.9%), respectively. The age-adjusted prevalence of myopia in the Han population was higher than that in the Mongolian population (31.8% vs. 23.0%, p < 0.001), but the prevalence of hyperopia was lower (25.8% vs. 35.3%, p = 0.002). In the multivariable logistic regression, ethnicity was associated with myopia (p = 0.001) and hyperopia (p = 0.001). Myopia was also associated with age, time spent in rural areas (p < 0.001) and middle/high school and undergraduate/graduate education levels (p = 0.027 and p < 0.001, respectively, compared with lower education levels). Additionally, age, height (p = 0.015) and pterygium (p = 0.014) were associated with hyperopia. Conclusions Ethnicity is closely related to RE in Inner Mongolia in mainland China. Our study investigates differences in prevalence of and risk factors for RE between the Han and Mongolian populations, which could not be explained by differences in the risk factors investigated in this study.

Prevalence and Risk Factors of Refractive Error in Qinghai, China: A Cross-Sectional Study in Han and Tibetan Adults in Xining and Surrounding Areas

“…Pterygium is another risk factor of hyperopia in our study apart from age, which was also found in the study conducted by our team in Inner Mongolia and Yunnan (17,18). Eyes with hyperopia tend to have thinner cornea and sclera, but thicker conjunctiva, which might increase the risk of pterygium (44)(45)(46).…”

“…Shorter time length in rural area, higher education level, lighter active level and lower BMI are risk factors for myopia in our study. Similar study conducted by our team in Inner Mongolia of China also found that longer time length in rural area decrease the risk of myopia(p < 0.001) (17). A study in Beijing with 681 students showed a much lower risk of myopia in rural area compared to that under urban settings (OR 0.17, p < 0.001) (35).…”

“…Interestingly, studies in more developed areas in Eastern China and Southeastern Asia focusing on Han population found similar prevalence of myopia (Table 4). Up to now, there are limited number of epidemiological studies about RE in elder adults in China (13,14,(17)(18)(19)(20)(21)(22)(23). The highest prevalence of myopia was observed in Liwan Eye Study in 2009, 32.3% in 1269 adults elder than 50 years (14), while the prevalence of myopia in Han population in our study is 32.93%.…”

“…After adjusted by sex, age, time length in rural area, education level, occupation, active level, BMI, pterygium, and smoking condition, the risk of myopia in Han population is considerably higher than that in Tibetan population (p < 0.001). Our research group also found that in Inner Mongolia, the myopia risk is signi cantly higher in Han population than Mongolian population, which is one of the biggest ethnic minorities in China (17). After investigating 10333 Chinese, Indian and Malaysian in Singapore, Pan CW found that Chinese is easier to be affected by myopia, high myopia and astigmatism compared to Indian and Malaysian (27).…”

“…The excessive use of eyes might explain the higher risk of myopia in population with higher education level (1,4,17,37). Terasaki H et al noticed the association between BMI and ocular length (38).…”