(Reuters Health) – Lifestyle changes during the COVID-19 pandemic such as more screen time and less outdoor time appear to be associated with an increased incidence of myopia among children, a study of youth in Hong Kong suggests.
Researchers examined data on two cohorts of children aged 6 to 8 years from the longitudinal Hong Kong Children Eye Study: one group recruited before the pandemic (n=1,084) that had a mean follow-up period of 37.5 months and one group recruited at the beginning of the pandemic (n=709) with a mean follow-up period of 7.9 months. The pre-pandemic cohort had been in the study for three years as of January 2020, while the pandemic cohort were recruited between December 1, 2019, and January 24, 2020.
All the participants had visual acuity exams and completed questionnaires on their lifestyle habits including how much time they spent outdoors and on screens, as well as other close-up visual tasks like reading.
Overall, the proportion of children with myopia during the pandemic increased from 19.4% at baseline to 35.3% at the 8-month follow-up, the study found. Over this same period, mean time spent outdoors declined from 1.27 to 0.41 hours a day and total time doing close visual work increased from 3.42 to to 8.02 hours daily driving largely by a surge in screen time.
“We found an alarming increase in myopia incidence over an 8-month period during which school closures were in effect and school children in Hong Kong were spending most of their time indoors with their smartphones, tablets, and computers for both school and after-school activities,” said senior study author Jason Yam, an associate professor in the Department of Ophthalmology and Visual Sciences at the Chinese University of Hong Kong.
Increase in near-work time has also been implicated as a lifestyle risk factor for myopia development, Yam said by email. There is consistent data showing that severe short-sightedness is related to the number of books read per week and close reading distance, but the mechanism is not yet well-understood, Yam added.
“Outdoor time has been consistently shown by multiple studies in different countries to have a protective role against the development of myopia, and is a top priority among international recommendations for myopia control strategies,” Yam said.
When researchers stratified youth by age, they found the 1-year incidence of myopia during the pandemic was 28% at 6 years, 27% at 7 years, and 26% at 8 years.
By contrast, the 1-year incidence of myopia pre-pandemic was 17% at 6 years, 16% at 7 years, and 15% at 8 years, researchers report in the British Journal of Ophthalmology.
During the COVID-19 pandemic, the change in spherical equivalent refraction (SER) and axial length was -0.50 ± 0.51 diopters and 0.29 ± 0.35 mm, respectively, the study found. Myopia was defined as SER less than or equal to -0.50 diopters.
One limitation of the study is that it relied on questionnaires to determine changes in lifestyle habits, which may be subject to recall bias. It’s also possible that the results from Hong Kong might not reflect what would happen in places with different practices for social distancing, school closures, and stay-at-home orders during the pandemic that may have impacted lifestyle habits.
Even so, the study results highlight the known risks factors of myopia onset and progression in school-aged children, and the impact of COVID-19 lifestyle modifications on myopia incidence, said Felicia Timmermann, an assistant professor of optometry at Nova Southeastern University in Fort Lauderdale, Florida, who wasn’t involved in the study.
“Clinicians can anticipate similar results in their own patient population and use this study to educate their patients and provide lifestyle recommendations and management modalities to address myopia in the pediatric population,” Timmermann said by email.
SOURCE: https://bit.ly/37unhmS British Journal of Ophthalmology, online August 2, 2021.
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