Prevalence and risk factors for refractive error in older adults in eight ethnicities in China: The China National Health Survey (CNHS)

doi:10.21203/rs.3.rs-2988452/v1

Download PDF

Research Article

Prevalence and risk factors for refractive error in older adults in eight ethnicities in China: The China National Health Survey (CNHS)

https://doi.org/10.21203/rs.3.rs-2988452/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

Background

China is a multiethnic country; however, the study of the prevalence of RE in western areas and in ethnic minorities in China is limited. This study was to investigate the prevalence and influences of REs (refractive errors) in older adults in the Han and minority ethnicities in 7 provinces in China.

Methods

The current cross-sectional study is part of the ophthalmic data of the China National Health Survey (CNHS). Face-to-face interviews and ophthalmic examinations were conducted in 7 provinces in Northwest and Southwest China. The age- and sex-adjusted prevalence of RE in Han and 7 other ethnicities, aged 50–80 years, were compared. A mixed effects model was used to identify the risk factors for RE.

Results

A total of 12902 participants, 8808 Han and 4102 ethnic minorities, were included. The age- and sex-adjusted prevalence of myopia, high myopia, hyperopia and astigmatism were ranged 15.3% (Manchu) -22.9% (Han), 0.2% (Yugur) -2.8% (Han), 21.6% (Tibetan) -48.9% (Uyghur) and 38.7% (Yi) -57.5% (Manchu) in different ethnicities, respectively. Compared to Han population, ethnicities of Mongolian, Tibetan, Uyghur, Yi and Yugur was less likely to have myopia, while there is no significant difference in the prevalence of myopia between the Manchu, Korean and Han ethnic groups. Other protective factors for myopia including: rural residence; higher BMI index, living in higher latitude area and smoking history. High myopia was negatively associated with Mongolian and Yugur populations and living in rural areas. Older age; ethnicities of Mongolian, Uyghur, Yi and Yugur; rural residence, living in higher latitude area and past smoking history were positively associated with hyperopia.

Conclusions

The prevalence of myopia in older adults was relatively low in Northwest China. Significant differences in RE prevalence were observed between minority ethnicities and Han people, except for the Manchu and Korean populations.

Refractive error

Myopia

Ethnicity

Risk factor

High myopia has become an important cause of low vision in adults. The early onset of myopia and the increased prevalence of myopia in schoolchildren have made this problem increasingly serious throughout the world[1–4]. Previous studies demonstrated that the prevalence of myopia was highest in East Asia[5–7]. In mainland China, many epidemiological investigations have reported the prevalence of RE, especially myopia, in the adult Han population in economically developed regions[8–10], which ranged from 25–36%. China is a multiethnic country; however, the study of the prevalence of myopia in western areas and in ethnic minorities in China is limited.

The China National Health Survey (CNHS) was conducted to study reference intervals for physiological constants among different ethnic populations in different areas. It is the first comprehensive multiethnic population data collection from different areas in China[11]. The RE data were collected in the western and northern minority areas in 7 provinces. The prevalence of myopia and high myopia in the minority ethnic population was significantly lower than that in the Han population in our previous studies of the CNHS program conducted in Yunnan[12], Qinghai[13] and Gansu[14] Provinces. A high education level, indoor work/near working, family history of myopia and living in urban areas have been reported to be risk factors for myopia with strong evidence[12–15].

The influence of ethnicity on myopia is complex. Ethnic factors include both genetics and the living environment. In multiethnic studies, Han ethnicity was associated with an increased risk of myopia compared with other ethnicities in some areas of China and in other regions[16, 17]. The current study integrated RE data from the CNHS program in 7 provinces with 7 ethnic minority groups. The differences in the prevalence of myopia between the Han population and ethnic minorities are very helpful for exploring the genetic and environmental risk factors for myopia.

Study population

Our study is part of the CNHS in China. CNHS is an ongoing cross-sectional study to evaluate the national health status using a multistage cluster sampling method conducted by the Chinese Academy of Medical Sciences (CMAS) and School of Basic Medicine, Peking Union Medical College (PUMC)[11]. The CNHS program was conducted in 7 provinces distributed in the Northeast region (Heilongjiang Province), Northwest region (Xinjiang Province), North region (Inner Mongolia), West region (Qinghai and Gansu Provinces), Middle region (Hebei Province) and Southwest region (Yunnan Province) in mainland China. The seven-province survey was conducted from 2013 to 2017 and included 7 provincial capitals (Shijiazhuang, Harbin, Huhehaote, Xining, Wulumuqi, Kunming and Lanzhou city), 5 middle-sized cities, 10 counties and 13 rural township regions. Individuals residing in the selected areas were all invited to participate in the study. The selected provinces were from regions selected based on their economic status and minority ethnic population size and distribution. Participants of different socioeconomic developmental levels, living environments and ethnicities were all recruited.

This study was approved by the institutional review board of the Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences.

Inclusion and exclusion criteria

The inclusion criteria for participant refraction metrics in this study were as follows: 1) aged 50–80 and 2) local resident for at least one year. The exclusion criteria were as follows: 1) women who were currently pregnant; 2) soldiers in service; 3) disabled individuals (who may not be able to complete the whole physical examination); 4) individuals with severe mental disorders; and 5) individuals who had eye diseases, including glaucoma, pterygium, retina disease, and eye surgical histories (including cataract surgery) or eye injury histories.

Measurements. A face-to-face questionnaire interview with all of the participants invited to the study center was conducted by experienced interviewers. Demographic, lifestyle and information on systemic diseases, such as birthplace, current address, ethnicity, education level, occupation, smoking status, alcohol consumption, activity level, body mass index (BMI) and medical history, were collected by the questionnaire. BMI was defined as weight (kg)/height (m)2. Educational level was divided into five groups (illiteracy, primary school, middle school, high school and university or higher). The occupational group included outdoor and indoor work. Occupational physical labor was divided into light, medium and heavy. Exercise status was divided into 5–7 days a week (at least 20 minutes per day), 3–4 days a week, 1–2 days a week, less than 3 days a month, and never exercising. We grouped physical labor and exercise activities together for the overall activity level. A heavy activity level was defined as exercising more than \(\ge\)5 days a week or doing heavy physical labor work. Smoking or alcohol consumption was divided into never-smoker/drinker past smoker/drinker and current smoker/drinker.

Assessment of RE. Noncycloplegic autorefraction and corneal curvature radius measurements were conducted by an experienced ophthalmologist using an autorefractor (ARK-510A, Nidek Co., Ltd., Tokyo, Japan). Anterior segment examination was performed with a hand-held slit lamp (KJ5S2, Suzhou Kangjie Medical Co. Ltd., Jiangsu, China). Spherical equivalent (SE) was used to evaluate the RE data, which was defined as a sphere plus half cylinder. In the current study, emmetropia, myopia and high myopia were defined as − 0.5 ≤ SE ≤ 0.5, SE < − 0.5D and SE < − 6.0D, respectively. Hyperopia was defined as SE > + 0.5D. Anisometropia was defined as a refractive cylinder > 0.5 D or<-0.5 D, and astigmatism was defined as a difference in SE between two eyes greater than 2.5.

Statistical analyses

Due to the homogeneity of the binocular refractive data, only data from the right eye were analyzed. The age- and sex-specific prevalence of myopia, high myopia, anisometropia, astigmatism and hyperopia in all data, in each ethnic group, as well as in the Han population for each province, were calculated. For all demographic, lifestyle-related, geographic information and physical examination data, the chi-squared test and analysis of variance were used to compare the categorical and continuous variances among the different provinces. Risk factors for anisometropia, astigmatism, myopia, high myopia and hyperopia were filtered through univariable logistic regression models. The Loess algorithm was used to visualize the relationships among ethnicities, provinces and refractive conditions, while a linear model was used to visualize the effect of latitude and BMI. To avoid risk factors overlapping in the same provinces, risk factors were identified through linear mixed effects models, using province as a horizontal data, which excluded factors that were insignificant in the univariable logistic models. A P value < 0.05 (two-tailed) was considered statistically significant. Age- and sex-standardization was performed by the direct method using the 6th national census (2010) data of the Chinese population as the standard population. All data analyses were performed using R version 4.2.2.

Population characteristics

A total of 12902 individuals, 5337 men and 7565 women, aged ≥ 50 years, were included in this survey. The response rate was 96.7%. The average proportion of the Han population was 68.2% in total, ranging from 58.1% in Qinghai to 82.9% in Heilongjiang. The mean urban residence proportion was 59.1%, ranging from 41.2% in Hebei to 90.5% in Inner Mongolia. A total of 15.6% of individuals were uneducated, ranging from 7.1% in Heilongjiang to 23.7% in Yunnan. The proportion of middle school education level was 24.5%, ranging from 16.4% in Gansu to 33.6% in Heilongjiang; education level of university or higher was 13.3%, ranging from 7.8% in Yunnan to 22.6% in Inner Mongolia. The proportion with a light activity level was 37.5%, ranging from 31.3% in Gansu to 44.0% in Qinghai. The indoor occupation proportion was 52.9%, ranging from 40.5% in Hebei to 75.9% in Inner Mongolia. The percentages of never smoking and never drinking were 67.1%, ranging from 63.8% in Inner Mongolia to 76.4% in Yunnan, and 54.8%, ranging from 45.5% in Gansu to 68.8% in Yunnan. A positive history of hypertension and diabetes was 34.4%, ranging from 26.1% in Xinjiang to 49.4% in Hebei and 9.8%, ranging from 6.5% in Yunnan to 13.5% in Hebei.

Prevalence of RE in 7 Provinces

The sex- and age-adjusted prevalence of RE in 8 ethnicities and provinces is presented in Table 1. The adjusted prevalence of anisometropia, astigmatism, myopia, high myopia, hyperopia and emmetropia was 4.4 [4, 4.9], 53.5 [51.9, 55.1], 21.4 [20.4, 22.4], 2.4 [2.1, 2.7], 37.8 [36.5, 39.1] and 40.8 [39.6, 42.1], respectively. The prevalence of myopia and high myopia ranged from 15.3 [12.7, 18.6] % in Manchu to 22.9 [21.8, 24.2]% in the Han population and from 16.8 [14.2, 20]% in Heilongjiang to 33 [28.5, 38.3]% in Qinghai Province; 0.2 [0, 4.2]% in Yugur to 2.8 [2.4, 3.3]% in the Han population and 1.2 [0.6, 2.3]% in Hebei to 4.1 [2.8, 5.9]% in Inner Mongolia Province, respectively. The prevalence of hyperopia ranged from 21.6 [16.8, 28]% in Tibetan to 48.9 [43.6, 54.8]% in the Uyghur population and 24.7 [20.2, 30.1]% in Qinghai to 45.9 [41.9, 50.3]% in Hebei Province.

Table 1

The prevalence distribution of RE in the 8 ethnicities and the 7provinces.
Race	Province	Anisometropia		Astigmatism		High myopia		Myopia		Hyperopia		Emmetropia
Race	Province	Crude rate / %	Adjusted rate /% [95% CI]	Crude rate / %	Adjusted rate / % [95% CI]	Crude rate / %	Adjusted rate / % [95% CI]	Crude rate / %	Adjusted rate / % [95% CI]	Crude rate / %	Adjusted rate / % [95% CI]	Crude rate / %	Adjusted rate / % [95% CI]
Mongolian		4.6	6.5 [3.5, 11.2]	44.3	53.1 [44.6, 63.2]	1.0	0.9 [0.2, 3.4]	18.6	19 [14.1, 25.3]	37.7	41.7 [34.4, 50.4]	43.8	39.4 [33.1, 47]
Tibetan		2.8	3.1 [1.6, 6.5]	38.4	46 [38.5, 55.0]	1.9	1.8 [0.7, 5]	22.2	22.4 [17.6, 28.6]	18.6	21.6 [16.8, 28]	59.2	56 [48.6, 64.8]
Uyghur		4.1	5.3 [3.5, 7.9]	42.7	47.3 [41.9, 53.5]	1.5	1.8 [0.8, 3.6]	13.8	17 [13.6, 21.1]	48.0	48.9 [43.6, 54.8]	38.2	34.2 [30, 39]
Yi		3.6	4.3 [1.9, 8.8]	34.3	38.7 [30.9, 48.2]	1.1	0.7 [0.2, 3.5]	13.9	15.4 [10.6, 22]	41.8	42.4 [34.6, 51.8]	44.3	42.3 [34.8, 51.3]
Korean		3.0	3.6 [1.5, 8.2]	58.1	54.9 [45.8, 66]	1.3	2.2 [0.5, 6.8]	16.9	21.4 [15.3, 29.8]	53.2	48.5 [40.2, 58.8]	29.9	30.1 [23.5, 38.7]
Manchu		2.8	2.8 [1.6, 4.9]	52.1	57.5 [51.4, 64.3]	1.9	1.3 [0.8, 2.7]	18.4	15.3 [12.7, 18.6]	36.0	43 [37.6, 49.3]	45.6	41.7 [37, 47]
Yugur		2.5	2.2 [1.2, 6.1]	39.4	44.7 [36.6, 54.9]	0.2	0.2 [0.0, 4.2]	14.1	15.8 [11.1, 22.8]	34.6	38.4 [31, 48]	51.3	45.8 [38.7, 54.9]
Han		4.0	4.5 [4.0, 5.1]	50.2	55 [53.1, 57]	2.9	2.8 [2.4, 3.3]	22.9	22.9 [21.8, 24.2]	32.8	36.4 [34.8, 38]	44.4	40.7 [39.3, 42.2]
	Hebei	2.8	3.8 [2.6, 5.5]	52.5	57.7 [53.1, 62.7]	1.0	1.2 [0.6, 2.3]	16.8	17.2 [14.8, 19.9]	44.1	45.9 [41.9, 50.3]	39.2	37 [33.6, 40.7]
	Heilongjiang	4.4	4.4 [3.1, 6.3]	52.7	57.5 [52.4, 63.1]	2.7	2.1 [1.4, 3.3]	16.5	16.8 [14.2, 20]	41.4	42.7 [38.5, 47.3]	42.2	40.5 [36.8, 44.7]
	Inner Mongolia	5.2	6.1 [4.4, 8.4]	47.8	52.1 [47, 57.8]	4.2	4.1 [2.8, 5.9]	26.6	26.2 [22.7, 30.2]	29.8	34.3 [30.1, 39]	43.6	39.5 [35.5, 44]
	Qinghai	4.6	4.4 [2.9, 6.9]	44.8	51.9 [45.7, 59]	4.3	3.4 [2.2, 5.6]	36.3	33 [28.5, 38.3]	17.3	24.7 [20.2, 30.1]	46.4	42.4 [37.3, 48.3]
	Xinjiang	4.9	5.2 [3.9, 6.8]	48.6	52.3 [48, 57.1]	3.2	3.4 [2.3, 4.7]	21.1	21.3 [18.6, 24.3]	37.0	38.6 [34.9, 42.6]	42.0	40.1 [36.5, 44.1]
	Yunnan	3.8	3.7 [2.4, 5.9]	47.3	51.4 [45.5, 58.1]	3.0	2.7 [1.5, 4.8]	24.3	24.3 [20.5, 28.8]	26.1	26.5 [22.4, 31.3]	49.6	49.3 [43.8, 55.5]
	Gansu	3.4	3.3 [2.4, 4.7]	52.2	55.7 [51.2, 60.7]	3.2	2.9 [2.1, 4.2]	25.2	25.4 [22.5, 28.6]	26.0	32.3 [28.8, 36.3]	48.8	42.3 [38.9, 46.1]
Total	Total	3.8	4.4 [4, 4.9]	48.4	53.5 [51.9, 55.1]	2.4	2.4 [2.1, 2.7]	21.0	21.4 [20.4, 22.4]	34.3	37.8 [36.5, 39.1]	44.8	40.8 [39.6, 42.1]
CI: Confidence interval. Age- and sex-standardization was performed by direct method using the 6th national census (2010) data of Chinese population as the standard population. Emmetropia, myopia and high myopia were defined as − 0.5 ≤ SE ≤ 0.5, SE < − 0.5D and SE < − 6.0D, respectively. Hyperopia was defined as SE > + 0.5D. Anisometropia was defined as a refractive cylinder > 0.5 D or<-0.5 D, and astigmatism was defined as a difference in SE between two eyes greater than 2.5.

Risk factors for RE

Myopia and High Myopia

Ethnicity and significant factors in the univariate analysis were analyzed by a mixed effects model, using provinces as a parallel variable. The influencing factors for myopia yielded by the logistic regression model of the total population are presented in Fig. 1(A). When compared to the 50–54 subgroup, aging was a negative factor for the prevalence of myopia (0.83 (0.74, 0.94), p = 0.003) in the 55–59 group and (0.72 (0.63, 0.82), p < 0.001) in the 60–64 group and had a positive influence on myopia in those older than 70 (1.36 (1.16, 1.59), p < 0.001). Compared to the Han population, Mongolian (0.62 (0.46, 0.84), p = 0.002), Tibetan (0.66 (0.52, 0.85), P = 0.001), Uyghur (0.63 (0.49, 0.81), p < 0.001), Yi (0.66 (0.47, 0.93), p = 0.018) and Yugur (0.66 (0.51, 0.85), p = 0.002) ethnicity had a protective effect against myopia. Leaving in rural areas was a protective factor against myopia (0.73 (0.65, 0.82), p < 0.001). Compared to illiteracy, an education level of high school (1.57 (1.33, 1.86), p < 0.001) and university or higher (2.82 (2.34, 3.39), p < 0.001) had a positive influence on myopia. A higher BMI index was negatively correlated with myopia (0.98 (0.97, 0.99), p = 0.003). Individuals with a diabetes history were more likely to have myopia (1.33 (1.13, 1.53), P < 0.001). A smoking history (past smoking: 0.8 (0.69, 0.92), p = 0.002; current smoking: 0.88 (0.79, 0.99), p = 0.034) and living in higher latitude area (0.72 (0.55, 0.95), p = 0.021) were negative factors for myopia. Activity level, working environment and latitude had no significant association with myopia.

The positive influences of high myopia are presented in Fig. 1(B). Compared to men, female participants had a higher possibility of high myopia (2.06 (1.39, 3.05) p < 0.001) in this survey. Compared to the Han population, the Mongolian (0.24 (0.09, 0.67), p = 0.007) and Yugur (0.07 (0.01, 0.48), p = 0.007) ethnicities had a lower risk of high myopia. Living in rural areas was a protective factor against high myopia (0.66 (0.47, 0.91), p = 0.013). An education level of university or higher was positively associated with high myopia (1.77, (1.11, 2.84), p = 0.017). Age, smoking history, BMI and working environment had no significant influence on high myopia in this 7-province survey.

Hyperopia

In this model, compared to the youngest age group (50–54), aging had a positive influence on hyperopia (all p < 0.001). Compared to the Han ethnicity, the Mongolian (1.54 (1.19, 2.00) p = 0.001), Uyghur (1.84 (1.52, 2.23), p < 0.001), Yi (1.86 (1.42, 2.45), p < 0.001) and Yugur (1.38 (1.12, 1.71), p = 0.002) populations had a higher risk of hyperopia while Manchu population (0.77(0.65,0.92), p = 0.004) had a protective effect on hyperopia. Compared to illiteracy, education levels of primary school (0.87 (0.77, 0.98), p = 0.024) or higher (all p < 0.001) were negatively associated with hyperopia. A past smoking history (1.15 (1.01, 1.30), p = 0.040) and living in higher latitude area (1.38 (1.03, 1.84), p = 0.031) were positively associated with hyperopia. Nevertheless, a hypertension history and drinking history had no significant influence on hyperopia in this model (Fig. 2(A)).

Emmetropia

In the mixed effects model, compared to the youngest group, older age was a protective factor against emmetropia (all p < 0.001), and women were less likely to have emmetropia (0.85 (0.78, 0.94), p = 0.001). Compared to the Han population, Tibetan (1.59(1.29, 1.96), p < 0.001) and Manchu (1.20 (1.01,1.42), p = 0.036) individuals were more likely to have emmetropia, while Uyghur (0.74 (0.61, 0.89), p = 0.001), Yi (0.75 (0.58, 0.97), p = 0.028) and Korean (0.72 (0.55, 0.94), p = 0.018) populations were less likely to have emmetropia. An education level of university or higher was negatively related to emmetropia (0.69 (0.59, 0.81), p < 0.001). Higher BMI (1.02 (1.01, 1.03), p < 0.001) and heavy activity level (1.12 (1.04, 1.21), p = 0.002) were positively related to emmetropia. In the mixed effects model, a history of hypertension or diabetes and latitude metrics had no significant influence on emmetropia (Fig. 2(B)).

Astigmatism

Compared to the youngest age group, individuals in age groups older than 55 (all p < 0.001) and female participants (1.22 (1.08,1.37), p < 0.001) were more likely to have astigmatism. Compared to the Han population, ethnicities of Tibetan (0.75 (0.61, 0.95) p = 0.007), Uyghur (0.77 (0.64, 0.93), p = 0.007), Yi (0.56 (0.42, 0.72), p < 0.001) and Yugur (0.62 (0.51, 0.75), p < 0.001) had a protective influence against astigmatism. A history of diabetes (1.29 (1.14, 1.46), p < 0.001) and outdoor working (1.12 (1.03, 1.21), p = 0.009) were positive factors for astigmatism. A current drinking history was a negative factor for astigmatism (0.88 (0.80, 0.97), p = 0.013). A history of hypertension, smoking history, activity level and latitude had no significant association with astigmatism in this multivariate regression model (Fig. 3(A)).

Anisometropia

In the mixed effects model, compared to the youngest group, age groups older than 55 (p < 0.001 or p = 0.003) and female sex (1.32 (1.08,1.61), p = 0.006) were positively associated with anisometropia. Ethnicity was not significantly related to anisometropia. Compared to urban residences, rural residences were less likely to have anisometropia (0.78 (0.63, 0.97), p = 0.028). A higher BMI was negatively related to anisometropia (0.97 (0.95, 1.00), p = 0.042). Education level was not significantly related to anisometropia in the multivariate regression model (Fig. 3(B)).

To our knowledge, this is the first study to explore the distribution of RE in older adults of different ethnicities in China. Most ethnic minorities have different living habits and biological parameters. The RE frequency was distributed differently in the minority and Han populations in the present study. Mongolian, Tibetan, Uyghur, Yi and Yugur ethnicities were less likely to have myopia, and Mongolian and Yugurs ethnicities were less likely to have high myopia than Han individuals. Compared to the Han population, the ethnicities of Korean and Manchu had no significant influence on myopia in this epidemiological investigation.

The distribution of RE in different ethnicities could be explained using the gene‒environment interaction model of myopia formation. Geographically, Mongolian, Tibetan, Uyghur and Yugur populations live in West China, where grassland is the main ecosystem, and the four ethnicities all have a nomadic lifestyle. That environment provides more outdoor activity time and less near working periods during childhood, and these two points have been proven to be protective factors against myopia in childhood[18, 19].

However, the Korean and Manchu ethnicities are distributed in Northeast China. The Manchu population settled in Hebei Province during the Qing Dynasty, and societal and behavioral fusion with the Han population of this ethnicity occurred hundreds of years ago. Korean individuals mostly subsist on aquaculture and agriculture. In a study of present-day genetic patterns in East Asians, principal component analysis showed different gene compositions in different ethnicities^[20]. More gene fusion and cultural exchange with the Han population occurred in the middle and northeast areas of China. The Mongolia, Uyghur and Yugur populations in Middle Asia have an admixture of genes from European ancestors[21–23]. These genetic and environmental differences may influence the formation of myopia, corresponding to previous studies[16].

A high prevalence of myopia and high myopia in the Han population in younger adults has been observed throughout the world. However, the differences in myopia frequency in older adults \(\ge 50\) years in different countries were not as obvious[24]. In the present study, the total myopia frequency was 22.9% in older Han adults, which was similar to that of the Europe Eye Epidemiology (E³) Consortium study (27.5% in those aged 55–59 years)[25] and the Gutenberg Health Study (29.3% in those aged 55–64% years)[26] and even lower in some epidemiological studies in the US (ranging from 30.7% in those aged 46–60 years to 36.1% in those aged 50–59 years)[27, 28]. Another reason for the relatively low myopia frequency in the Han population in the present study compared to other epidemiological studies is that this epidemiological investigation used a large multiethnic population-based sampling strategy. In the areas with large ethnic minorities, the living environment of the Han population is more similar to that of minorities. A previous study revealed that there was no well-defined evidence of fundamental differences in the genetic background of myopia risk between Asian and European populations[29]. However, a more rapid myopia progression in childhood-onset myopia in Asians than in Hispanics, Blacks and Native Americans has been reported[30, 31]. Genetic influences may play a more important role in childhood-onset myopia.

Other risk factors for myopia in this study were consistent with previous studies. Individuals in the 55- to 64-year-old age group were less likely to have myopia, and after reaching 70 years, an increase in myopia occurred because of primary nuclear cataract formation. Rural residence provided more outdoor activity time, and higher education levels implied more near work time. The influence of diabetes on myopia in older adults in this study may have resulted from lens expansion caused by high blood glucose levels[32]. However, studies on the relationship between diabetes and myopia remain controversial. Some studies found a positive relationship between diabetes and myopia[33, 34], while no significant relationship was revealed in other studies[35, 36]. The reasons for these diverse results may be the different blood glucose control levels of the patients included in the different studies. In the present study, we also found an interesting relationship between latitude and myopia formation. Individuals in higher latitude area was less likely to have myopia in the present study. Higher latitude area means less sunshine duration in day time especially in winter and longer sunshine duration in summer. A study of the prevalence and possible factors of myopia in Southeast Norway (60\(^\circ\) latitude North) showed an extremely low myopia prevalence (13% in 16-19-year-old Norwegian Caucasians). The reverse of myopia trend in Norway couldn’t be explained by the difference of sunshine duration compared to Asian area, that may be explained by the different education pattern and culture. Preschool and school children in Norway spent 3–5 hours outdoors per day at school[37], and additional outdoor time after school for outdoor activity is a part of Norwegian culture[38]. The significant influence of latitude to myopia in our study may simply show the distribution of myopia in different latitude area.

The rapid increase in high myopia-induced vision impairment in adults has become a social problem and economic burden worldwide, especially in East Asia[4]. The prevalence of high myopia in university students in East Asia was 16%-28% in recent studies[39, 40]. Preventing moderate myopia progression to high myopia has become an important research issue[18]. In the present study, the risk factors for high myopia were different from those for myopia. Except for ethnicity, only sex, high education level and living in rural areas were associated with high myopia. An education level of university or higher as a risk factor for high myopia indicated that strong education stress and more study time could promote the formation of high myopia. Living in rural areas can guarantee more outdoor activity time. More outdoor activity and less near work could also provide protection against myopia progression to high myopia. Avoiding the early onset of myopia and slowing myopia progression would be critical to diminish the epidemic of high myopia in younger populations.

In the mixed effects model, the risk factors for hyperopia also showed an ethnic difference. The Mongolian, Yi, Uyghur and Yugur populations were more likely to have hyperopia, and Manchu ethnicity was less likely to have hyperopia compared to the Han population. In a study of ethnicity differences among Chinese and other races for hyperopia in the US, a lower prevalence of hyperopia was observed in Chinese people[28]. A lower frequency of hyperopia is consistent with a higher frequency of myopia in the Chinese population. A higher education level was negatively related to hyperopia, and older age was positively related to hyperopia in the present study, which is consistent with previous studies[28, 41]. The significant risk factors for hyperopia are the reverse of the risk factors for myopia.

The strengths of our study include a large multiethnic population-based sampling strategy, a detailed questionnaire and a high response rate. However, there are limitations of the present study. Due to the nature of its cross-sectional design, conclusions about causal effects regarding risk factors for myopia could not be reached. The study population was only older adults, and thus, the external validity was limited. Ocular axial length and other biometric data were not measured in our study. Finally, in the present study, myopia caused by primary cataracts was not excluded, and the mixed sample may influence the prevalence as well as the estimation of the association of risk factors and axial myopia, especially in the older group.

For the first time, we described the distribution of RE in older adults in the minority ethnicities of the Mongolian, Tibetan, Uyghur, Yugur, Manchu, Korean, Yi and Han populations in 7 provinces in North and West China. A lower prevalence of myopia was obtained in the present study than that in other studies conducted in well-developed areas in China. Significant differences in myopia, high myopia and hyperopia prevalence were observed between minority ethnicities and Han people, except for the Manchu and Korean populations. Other protective factors against myopia included age under 64 years, lower education level, living in rural areas, higher BMI and smoking history. Significant influencing factors of hyperopia were age, race, living environment, past smoking history and education level.

REs Refractive errors

CNHS The China National Health Survey

BMI Body mass index

SE Spherical equivalent

Acknowledgements: We appreciate the help from the local medical institution and CDC for data collection in the present study.

Author Contributions: XW analyzed and interpreted the data and drafted the manuscript. GS, TC, XW, LG, JC, YW and LP assisted with the acquisition of the data. GS, LP, YZ and JM designed the study. GS, RL, HH and YC helped develop the statistical method. YZ, JM revised the final manuscript. All authors read and approved the final manuscript.

Founding This study was supported by the National Science and Technology Pillar Program during the Twelfth Five-Year Plan Period sponsored by the Ministry of Science and Technology of China (Grant 2012BAI37B02).

Data availability

The data that support the findings of this study are available from the correspondence author.

Competing interests

None for any authors in this study.

Ethics approval and consent to participate

All methods were carried out in accordance with relevant guidelines and regulations in the present study. And this study was approved by the institutional review board of the Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences. All participants provided informed, written consent and all data were anonymized prior to analysis.

Consent for publication

Not applicable.

Nemeth J, Tapaszto B, Aclimandos WA, Kestelyn P, Jonas JB, De Faber JHN, et al. Update and guidance on management of myopia. European Society of Ophthalmology in cooperation with International Myopia Institute. Eur J Ophthalmol. 2021;31(3):853–83.
Li SM, Wei S, Atchison DA, Kang MT, Liu L, Li H, et al. Annual Incidences and Progressions of Myopia and High Myopia in Chinese Schoolchildren Based on a 5-Year Cohort Study. Invest Ophthalmol Vis Sci. 2022;63(1):8.
Han X, Liu C, Chen Y, He M. Myopia prediction: a systematic review. Eye (Lond). 2022;36(5):921–9.
Sankaridurg P, Tahhan N, Kandel H, Naduvilath T, Zou H, Frick KD, et al. IMI Impact of Myopia. Invest Ophthalmol Vis Sci. 2021;62(5):2.
Nakao SY, Miyake M, Hosoda Y, Nakano E, Mori Y, Takahashi A, et al. Myopia Prevalence and Ocular Biometry Features in a General Japanese Population: The Nagahama Study. Ophthalmology. 2021;128(4):522–31.
Edwards MH, Lam CS. The epidemiology of myopia in Hong Kong. Ann Acad Med Singap. 2004;33(1):34–8.
Han SB, Jang J, Yang HK, Hwang JM, Park SK. Prevalence and risk factors of myopia in adult Korean population: Korea national health and nutrition examination survey 2013–2014 (KNHANES VI). PLoS ONE. 2019;14(1):e0211204.
He M, Huang W, Li Y, Zheng Y, Yin Q, Foster PJ. Refractive error and biometry in older Chinese adults: the Liwan eye study. Invest Ophthalmol Vis Sci. 2009;50(11):5130–6.
Liang YB, Wong TY, Sun LP, Tao QS, Wang JJ, Yang XH, et al. Refractive errors in a rural Chinese adult population the Handan eye study. Ophthalmology. 2009;116(11):2119–27.
He J, Lu L, He X, Xu X, Du X, Zhang B, et al. The Relationship between Crystalline Lens Power and Refractive Error in Older Chinese Adults: The Shanghai Eye Study. PLoS ONE. 2017;12(1):e0170030.
He H, Pan L, Pa L, Cui Z, Ren X, Wang D, et al. Data Resource Profile: The China National Health Survey (CNHS). Int J Epidemiol. 2018;47(6):1734–1735f.
Wang M, Cui J, Shan G, Peng X, Pan L, Yan Z, et al. Prevalence and risk factors of refractive error: a cross-sectional Study in Han and Yi adults in Yunnan, China. BMC Ophthalmol. 2019;19(1):33.
Wang M, Gan L, Cui J, Shan G, Chen T, Wang X, et al. Prevalence and risk factors of refractive error in Qinghai, China: a cross-sectional study in Han and Tibetan adults in Xining and surrounding areas. BMC Ophthalmol. 2021;21(1):260.
Wang X, He H, Wang X, Shan G, Tao Z, Pan L, et al. Prevalence and risk factors of myopia in Han and Yugur older adults in Gansu, China: a cross-sectional study. Sci Rep. 2020;10(1):8249.
Morgan IG, Wu PC, Ostrin LA, Tideman JWL, Yam JC, Lan W, et al. IMI Risk Factors for Myopia. Invest Ophthalmol Vis Sci. 2021;62(5):3.
Cumberland PM, Bountziouka V, Hammond CJ, Hysi PG, Rahi JS, Eye UKB, Vision C. Temporal trends in frequency, type and severity of myopia and associations with key environmental risk factors in the UK: Findings from the UK Biobank Study. PLoS ONE. 2022;17(1):e0260993.
Shi Y, Wang Y, Cui A, Liu S, He X, Qiu H, et al. Myopia prevalence and ocular biometry: a cross-sectional study among minority versus Han schoolchildren in Xinjiang Uygur autonomous region, China. Eye (Lond). 2022;36(10):2034–43.
Morgan IG, French AN, Ashby RS, Guo X, Ding X, He M, et al. The epidemics of myopia: Aetiology and prevention. Prog Retin Eye Res. 2018;62:134–49.
Pan CW, Qian DJ, Saw SM. Time outdoors, blood vitamin D status and myopia: a review. Photochem Photobiol Sci. 2017;16(3):426–32.
Yu X, Li H. Origin of ethnic groups, linguistic families, and civilizations in China viewed from the Y chromosome. Mol Genet Genomics. 2021;296(4):783–97.
Su B, Xiao J, Underhill P, Deka R, Zhang W, Akey J, et al. Y-Chromosome evidence for a northward migration of modern humans into Eastern Asia during the last Ice Age. Am J Hum Genet. 1999;65(6):1718–24.
Lai SP, Ren HM, Hu HT, Li SB, Lai JH, Yan CX, et al. HLA-DRB alleles polymorphism in Han, Hui, Uygur and Tibetan populations in northwestern China. Yi Chuan Xue Bao. 1999;26(5):447–57.
Xu S, Huang W, Qian J, Jin L. Analysis of genomic admixture in Uyghur and its implication in mapping strategy. Am J Hum Genet. 2008;82(4):883–94.
Pan CW, Ramamurthy D, Saw SM. Worldwide prevalence and risk factors for myopia. Ophthalmic Physiol Opt. 2012;32(1):3–16.
Williams KM, Verhoeven VJ, Cumberland P, Bertelsen G, Wolfram C, Buitendijk GH, et al. Prevalence of refractive error in Europe: the European Eye Epidemiology (E(3)) Consortium. Eur J Epidemiol. 2015;30(4):305–15.
Wolfram C, Hohn R, Kottler U, Wild P, Blettner M, Buhren J, et al. Prevalence of refractive errors in the European adult population: the Gutenberg Health Study (GHS). Br J Ophthalmol. 2014;98(7):857–61.
Russo D, Bass O. Visual and Ocular Conditions among a Homeless Adult Population of Boston. Optom Vis Sci. 2021;98(4):362–6.
Varma R, Torres M, McKean-Cowdin R, Rong F, Hsu C, Jiang X. Chinese American Eye Study G: Prevalence and Risk Factors for Refractive Error in Adult Chinese Americans: The Chinese American Eye Study. Am J Ophthalmol. 2017;175:201–12.
Tedja MS, Haarman AEG, Meester-Smoor MA, Kaprio J, Mackey DA, Guggenheim JA, et al. IMI - Myopia Genetics Report. Invest Ophthalmol Vis Sci. 2019;60(3):M89–M105.
Lisa A, Jones-Jordan LTS, Raymond H, Chu SA, Cotter, Robert N, Kleinstein REM, Donald O, Mutti J, Daniel Twelker, Karla Zadnik; for the CLEERE Study Group. and : Myopia Progression as a Function of Sex, Age, and Ethnicity. IOVS 2021, 62(10).
Lee SS, Lingham G, Sanfilippo PG, Hammond CJ, Saw SM, Guggenheim JA, et al. Incidence and Progression of Myopia in Early Adulthood. JAMA Ophthalmol. 2022;140(2):162–9.
Ji L, Cheng L, Yang Z. Upregulations of Clcn3 and P-Gp Provoked by Lens Osmotic Expansion in Rat Galactosemic Cataract. J Diabetes Res. 2017;2017:3472735.
Tarczy-Hornoch K, Ying-Lai M, Varma R. Los Angeles Latino Eye Study G. Myopic refractive error in adult Latinos: the Los Angeles Latino Eye Study. Invest Ophthalmol Vis Sci. 2006;47(5):1845–52.
Lin HT, Zheng CM, Fang YA, Liu JC, Wu YC, Chang YH, et al. Prevalence and risk factors for myopia in Taiwanese diabetes mellitus patients: a multicenter case-control study in Taiwan. Sci Rep. 2021;11(1):8195.
Cheng CY, Hsu WM, Liu JH, Tsai SY, Chou P. Refractive errors in an elderly Chinese population in Taiwan: the Shihpai Eye Study. Invest Ophthalmol Vis Sci. 2003;44(11):4630–8.
Attebo K, Ivers RQ, Mitchell P. Refractive errors in an older population: the Blue Mountains Eye Study. Ophthalmology. 1999;106(6):1066–72.
Moser TM. The outdoor environment in Norwegian kindergartens as pedagogical space for toddlers’ play, learning and development. Eur Early Child Educ Res J. 2010;18:457–71.
Hagen LA, Gjelle JVB, Arnegard S, Pedersen HR, Gilson SJ, Baraas RC. Prevalence and Possible Factors of Myopia in Norwegian Adolescents. Sci Rep. 2018;8(1):13479.
Bai X, Jin N, Wang Q, Ge Y, Du B, Wang D, et al. Development pattern of ocular biometric parameters and refractive error in young Chinese adults: a longitudinal study of first-year university students. BMC Ophthalmol. 2022;22(1):220.
Lee YY, Lo CT, Sheu SJ, Yin LT. Risk factors for and progression of myopia in young Taiwanese men. Ophthalmic Epidemiol. 2015;22(1):66–73.
Hashemi H, Khabazkhoob M, Iribarren R, Emamian MH, Fotouhi A. Five-year change in refraction and its ocular components in the 40- to 64-year-old population of the Shahroud eye cohort study. Clin Exp Ophthalmol. 2016;44(8):669–77.

No competing interests reported.

Download PDF

Version 1

posted

You are reading this latest preprint version

Prevalence and risk factors for refractive error in older adults in eight ethnicities in China: The China National Health Survey (CNHS)

Status:

Version 1

Abstract

Background

Methods

Results

Conclusions

Figures

Background

Methods

Study population

Inclusion and exclusion criteria

Statistical analyses

Results

Population characteristics

Prevalence of RE in 7 Provinces

Risk factors for RE

Myopia and High Myopia

Hyperopia

Emmetropia

Astigmatism

Anisometropia

Discussion

Conclusion

Abbreviations

Declarations

References

Additional Declarations

Status:

Version 1