Eur J Epidemiol (2013) 28:1001–1004 DOI 10.1007/s10654-013-9858-z
LETTER TO THE EDITOR
The effect of the Chinese Cultural Revolution and Great Leap Forward on the prevalence of myopia Ya Xing Wang • Liang Xu • Jost B. Jonas
Received: 16 August 2013 / Accepted: 3 October 2013 / Published online: 6 November 2013 Ó Springer Science+Business Media Dordrecht 2013
The Great Leap Forward was a campaign from 1958 to 1961 aiming to rapidly transform China from an agrarian economy into a modern industrialized communist society by the process of rapid industrialization and collectivization. It resulted in mass starvation in many provinces in China. The general disorganization and partial collapse of many parts of public life markedly affected the educational systems so that many schools were either closed or were open only part time. Also, many parents could not afford to send their children to school. After some years of economic re-growth, the Great Leap Forward was followed by the Cultural Revolution from 1966 to 1976. From the sudden start of the Cultural Revolution in 1966 onwards, schools were closed for 1–2 years. School education was only slowly re-institutionalized during the following period of 8 years until the Cultural Revolution ended in 1974. Myopia or shortsightedness is a potentially blinding disorder and has markedly gained in importance in China, since its prevalence profoundly increased in the young generation [1]. Recent investigations revealed that a higher prevalence of myopia in children is associated with a higher type of school attended and with more time spent with indoors studying or with less time spent on outdoor activities [2–6]. If the amount of intensive intellectual education with a high amount of indoors studying is a risk Y. X. Wang L. Xu (&) J. B. Jonas (&) Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, China e-mail:
[email protected] J. B. Jonas e-mail:
[email protected] J. B. Jonas Department of Ophthalmology, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Mannheim, Germany
factor for the development of myopia, we postulated that the age groups, which were school children at the time of the Great Leap Forward or during the Cultural Revolution, may have a lower prevalence of myopia than the age groups which were older or younger. We therefore analyzed the prevalence of myopia in a population-based study on adult residents of Beijing and compared the refractive error and ocular biometric parameters between age groups. The refractive error as a measure of myopia is strongly associated with the axial length and corneal curvature of the eye. The latter two parameters are measured by biometry. Since the myopic refractive error can increase at older age due to an age-related increase in the refractive power of the lens, we took the axial length and the ratio of axial length to corneal curvature (AL/CR) as surrogates of myopia [7]. Since the AL/CR ratio includes corneal refractive power, AL/CR as compared to axial length as single parameter is a better correlate for refractive error. Axial length and corneal curvature do not show marked age-related changes beyond an age of 30 years. The whole study was divided into two parts. The crosssectional part included all participants of the populationbased Beijing Eye Study 2011 who had undergone biometric measurement of axial length and corneal curvature [8]. The second study part included all participants of the Beijing Eye Study 2011 and all participants of the baseline examination in 2001 (Beijing Eye Study 2001), for whom the refractive error was measured, who had not previously undergone cataract surgery, and whose age fell into the age groups of 56–58 or 59–61 years [8]. The Medical Ethics Committee of the Beijing Tongren Hospital approved the study protocol and all participants gave informed written consent. Out of 4,403 eligible individuals in 2011, 3,468 (78.8 %) subjects participated. All study participants underwent a detailed interview and ophthalmic
123
1002
Y. X. Wang et al.
Fig. 1 Diagram showing the distribution of the ratio of axial length divided by corneal curvature as surrogate for myopia and age in the Beijing Eye Study 2011
examination. Using optical low-coherence reflectometry (Lensstar 900Ò Optical Biometer, Haag-Streit, Koeniz, Switzerland), biometry was carried out. Statistical analysis was performed using a statistical software package (SPSS for Windows, version 21.0, IBM-SPSS, Chicago, IL). In the cross-sectional study part, we assessed associations between the AL/CR ratio or axial length and ocular and systemic parameters, first in univariate analysis, followed by multivariate analyses. In the second study part, we compared the refractive status of groups with the same age but born in a different era. In the cross-sectional study part, mean AL/CR was 3.05 ± 0.13 mm (median 3.04; range 2.55–4.11). In univariate analysis, AL/CR was significantly associated with older age (Fig. 1), male gender, greater body height and body mass index, higher educational level, and urban region of habitation; and with thicker cornea, larger corneal diameter, deeper anterior chamber, thinner lens, more myopic refractive error, and lower best corrected visual acuity. In multivariate linear regression analysis, AL/CR remained to be significantly associated with older age, higher educational level, urban region of habitation, deeper anterior chamber, thicker lens, and more myopic refractive error (Table 1). If instead of age the group of subjects born in 1946 or later versus the remaining elderly subjects were put into the multivariate analysis, a similar result was obtained. AL/CR was significantly associated with the older age group versus the younger group (P \ 0.001;
123
standardized correlation beta 0.13; regression coefficient B 0.03; 95 % CI 0.03, 0.04). As shown on the diagram of the association between AL/CR and age, the curve of the AL/CR showed two dips: one for the birth age group from 1958 to 1961, and second one for the birth age group from 1946 to 1949 (Fig. 1). The AL/CR was significantly (P = 0.04) lower in the age group born between 1958 and 1961 than in the next age group born between 1954 and 1957, and it was significantly (P \ 0.001) lower in the age groups born between 1946 and 1949 than in the age groups born between 1942 and 1945 or 1938 and 1941 (Fig. 1). In a similar manner, AL/ CR was significantly (P \ 0.001) lower in the age groups born between 1961 and 1946 than in the age groups born between 1945 and 1930 (Fig. 1). Correspondingly, analysis of variance revealed a significant association between AL/ CR and age (P \ 0.001). In the longitudinal study part study, the refractive error in the age group of 56–58 years (-0.12 ± 1.46 D vs. -0.51 ± 2.19 D; P = 0.007) and in the age group of 59–61 years (-0.14 ± 2.02 D vs. -0.56 ± 3.00 D; P = 0.03) was significantly less myopic in the cohort 2011 than in the cohort 2001. Correspondingly, the prevalence of myopia (refractive error \-1.0 D) in the age group of 56–58 years (15.2 ± 1.8 vs. 21.8 ± 2.1 %; P = 0.02) and in the age group of 59–61 years (12.5 ± 1.8 vs. 22.5 ± 2.0 %; P \ 0.001) was significantly lower in the cohort 2011. In a parallel manner, the prevalence of myopia defined as a refractive error \-3.0 D and as a
Great Leap Forward, Cultural Revolution and myopia Table 1 Multivariate analysis of associations between the ratio of axial length divided by corneal curvature radius and systemic and ocular parameters in the Beijing Eye Study 2011
P value = statistical significance of the association, CI = confidence interval
1003
P value
Regression coefficient (nonstandard beta)
95 % CI of un-standardized regression coefficient
Standardized regression coefficient
Systemic parameters Age (years)
\0.001
0.002
0.002, 0.023
0.17
Level of education
\0.001
0.007
0.005, 0.010
0.06
Rural/urban region
\0.001
0.10
0.004, 0.016
0.04
Anterior chamber depth (mm)
\0.001
0.16
0.15, 0.16
0.42
Lens thickness (mm)
\0.001
0.03
Refractive error (diopters): spherical equivalent
\0.001
-0.04
refractive error \-6.0 D (high myopia) was significantly lower in the cohort 2011 than in the cohort 2001 for the age groups of 56–58 years (5.6 ± 1.0 vs. 7.4 ± 1.2 % (P \ 0.001); and 0.6 ± 0.3 vs. 2.2 ± 0.7 % (P \ 0.001), respectively) and for the age groups of 59–61 years (6.6 ± 1.2 vs. 11.7 ± 1.3 % (P \ 0.001); and 2.4 ± 0.7 vs. 3.8 ± 0.8 % (P \ 0.001), respectively). The age group of 56–61 years in the cohort 2011 represented the birth age group 1950–1955. The risk factors for myopia operate largely over the ages at which children become myopic, primarily from the age of around 5 to about 15–20 years. We found that the AL/ CR ratio reached a peak for the cohort born in 1938–1941 with a slight decline for the cohort born 1942–1945 (Fig. 1). The oldest in these birth cohorts went through their peak vulnerability to the development of myopia in the period from 1943 to 1953, while the youngest went through the myopia vulnerability period from about 1948 to approximately 1958. It suggests that the cohorts with a relatively high amount of myopia just had left school when the Great Leap Forward started in 1958. Correspondingly, the cohort born 1946–1949 showed a drop in the AL/CR ratio (i.e., a decrease in myopia) (Fig. 1). For this cohort, the relevant years for the development of myopia were 1951–1961 and 1954–1964. The substantial drop in the AL/CR ratio (cohort 1946–1949) corresponded to the period of the Great Leap Forward. After the cohort 1946–1949, the AL/CR ratio stabilized or slightly increased (i.e., an increase in myopia) up to the cohort born 1954–1957, after which the AL/CR ratio again dropped in the cohort born 1958–1961 (Fig. 1). The latter cohort was the age group whose education was almost completely disrupted during the Cultural Revolution from 1966 to 1974. Correspondingly, when comparing the cohort from 2001 and from 2011, the prevalence of myopia including of high myopia (refractive error \-6 diopters) was lower in the birth age group 1950–1955 than in the birth age group 1940–1945. Altogether, the data indicate a hyperopic (i.e., less myopic) shift for the generation born in the years from
0.02, 0.04 -0.04, -0.04
0.08 -0.65
1946 to 1961, with two major dips for the group from 1946 to 1949 and from 1958 to 1961. This is in contrast to the markedly higher AL/CR ratio (i.e., increase in myopia) for the generations borne before 1946, and it is in striking contrast to the general shift to marked myopization in the young generations in the large metropolitan centers like Beijing nowadays with a myopia prevalence of [80 % in the 18-years-old teenagers [9, 10]. Despite limitations of our study (retrospective study design; widespread starvation and malnutrition of adolescents could have resulted in shorter body stature and, due to an association between body height and axial length, to shorter eye globes), the findings suggest that the pronounced disruption in schooling during the Great Leap Forward and the Cultural Revolution has resulted in a marked reduction in the prevalence of myopia with a slight recovery in the period between the Great Leap Forward and the Cultural Revolution in China. Acknowledgments Supported by National Natural Science Foundation of China. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Conflict of interest interests exist.
The authors have declared that no competing
References 1. Morgan IG, Ohno-Matsui K, Saw SM. Myopia. Lancet. 2012;379:1739–48. 2. Wong TY, Foster PJ, Hee J, Ng TP, Tielsch JM, Chew SJ, Johnson GJ, Seah SK. Prevalence and risk factors for refractive errors in adult Chinese in Singapore. Invest Ophthalmol Vis Sci. 2000;41:2486–94. 3. Rose KA, Morgan IG, Smith W, Burlutsky G, Mitchell P, Saw SM. Myopia, lifestyle, and schooling in students of Chinese ethnicity in Singapore and Sydney. Arch Ophthalmol. 2008;126:527–30. 4. Low W, Dirani M, Gazzard G, Chan YH, Zhou HJ, Selvaraj P, Au Eong KG, Young TL, Mitchell P, Wong TY, Saw SM. Family history, near work, outdoor activity, and myopia in Singapore Chinese preschool children. Br J Ophthalmol. 2010;94:1012–6.
123
1004 5. Sharma A, Congdon N, Gao Y, Lu Y, Ye Y, Wu J, Lam DS, Li L, Wu J, Tse YK, Zhang M, Song Y, Griffiths S. Height, stunting, and refractive error among rural Chinese schoolchildren: the See Well to Learn Well project. Am J Ophthalmol. 2010;149:347–53. 6. Guggenheim JA, Northstone K, McMahon G, Ness AR, Deere K, Mattocks C, Pourcain BS, Williams C. Time outdoors and physical activity as predictors of incident myopia in childhood: a prospective cohort study. Invest Ophthalmol Vis Sci. 2012;53: 2856–65. 7. Grosvenor T. High axial length/corneal radius ratio as a risk factor in the development of myopia. Am J Optom Physiol Opt. 1988;65:689–96.
123
Y. X. Wang et al. 8. Zhou JQ, Xu L, Wang S, Wang YX, You QS, Tu Y, Yang H, Jonas JB. The 10-year incidence and risk factors of retinal vein occlusion: the Beijing Eye Study. Ophthalmology. 2013;120: 803–8. 9. Zhao JL, Pan XJ, Sui RF, Pan XJ, Mao J, Li CR, Jiang LJ, Qiu CL, Chen SG, Liu QY. Refractive error study in children: results from Shunyi district, China. Am J Ophthalmol. 2000;129:427–35. 10. He M, Huang W, Zheng Y, Huang L, Ellwein LB. Refractive error and visual impairment in school children in rural southern China. Ophthalmology. 2007;114:374–82.
