Sleep less, myopia more

Objective: To evaluate the association between sleeping time and myopia in children. Methods: The data from 15316 Chinese schoolstudents aged 6 to 18 years from 19 randomizedschools in Beijing cityincludingthe cycloplegicrefractor and the possible genetic, environmental and behavioral habitrisk factors (parental myopia, parental education, reading or writing distance, hours of sports,hoursof watching TV or using computer, and hours of sleeping)were evaluated to explore the key risk factors for myopia. Univariate and multiplelogisticregression analysis were performed, and receiver operator characteristic (ROC) curves generated. Differences among the areas under ROC curves were compared using the method of multiple comparison with the best. Results: After controlling for age, gender, parental myopia, father’s education, reading or writing distance, hours of sports, hours of watching TV or using computer per day, hours of studying per day, myopia was associated with short sleeping time (lowest time span) versus long sleeping time (highest time span) (odds ratio=3.37; 95%CI 3.07-3.70). Controlling for the same factors, children with shorter sleeping time had significantly more myopic refractions (-1.69D for children with the shortest sleeping time compared with -1.29D for children with the longest sleeping time per day). Aanlysis of the areas under the ROC curves showed five variables with predictive values better than chance: age, sleeping time, reading or writing distance, hours of studying, and parent’s myopia. Conclusion: Sleeping time may be an independent risk factor of myopia, and this relationship may not be explained merely by increased hours of studying or hours of watching TV. An interesting observation is that sleeping time may be an important risk factor for myopia compared with other near work factors. The complexity of the relationship between sleeping time and myopia need additional studies to clarify any cause-effect relationship.