In China, the risk is lower for poorer students
Chinese researchers found that lower-income students have a lower incidence of myopia than their middle-class peers. These findings are based on a study of 20,000 students in which twice the prevalence of myopia was found in the middle-income province of Shaanxi compared to the poorer province of Gansu.
This population-based study, published in Ophthalmology, was initiated in 2012 and was jointly conducted by Chinese government agencies and Stanford University. The researchers subjected approximately 20,000 4th and 5th grade students to visual examinations: 9,489 students in Shaanxi province and 10,137 students in Gansu province, the second poorest province in China.
The results of the study are as follows:
- the prevalence of clinically significant myopia in the middle-income province of Shaanxi was 23%: about twice the rate found in the poorer province of Gansu, where it was 12.7%.
- Living in a middle-income area was associated with a 69% increased risk of myopia, even after considering other risk factors such as time spent reading, outdoor activities and whether parents wore glasses.
- Higher grades in mathematics were always associated with greater myopia in all boys.
- myopia was generally less prevalent in males.
Students in lower-income areas were found to use the blackboard more for learning during classroom activities, as they could not afford to buy books; whereas students in middle-income areas used the blackboard much less. The researchers found that blackboard use had a 'protective effect' against myopia (when taken as the only variable), probably because it did not require the type of close-up focusing that can contribute to myopia. However, when combined with the other risk factors, it did not reach a statistically significant value.
Prof. Nathan Congdon, head of the research project, stated that "We will continue to search for a plausible explanation and I believe that the results of this research merit further investigation into the effects on myopia of the increased use of blackboards instead of books, as well as the role of other concomitant causal factors".
For more information read the paper published on the Stanford University website
Dr. Carmelo Chines
Direttore responsabile
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