Physically active children have healthier retinal vasculature

The Hong Kong Children Eye Study in nearly 12,000 local children aged 6–8 years shows that increased physical activity is associated with healthier retinal microvasculature.

As microvasculature and systemic circulation share similar anatomic and physiological characteristics, previous research suggests that microvasculature can serve as a marker of systemic vascular health, and that it can be implicated in cardiovascular (CV), respiratory, renovascular and neurovascular diseases. [Circ Res 2019;124:1796-1807; Eur Heart J 2021;42:2590-2604; Am J Med 2022;135:1059-1068] Although several studies have investigated effects of physical activity and inactivity on retinal vasculature in adults, their effects in children remain less explored. [Invest Ophthalmol Vis Sci 2011;52:6522-6528; Front Physiol 2018;9:176]

“In this study, we utilized a newly developed and validated artificial intelligence [AI] deep learning system [DLS] to measure retinal arteriolar and venular caliber in children, and investigated the effects of physical activity and inactivity on their retinal vasculature. Our primary hypothesis was that increased activity would be associated with healthier retinal vasculature, as characterized by wider arterioles and narrower venules,” wrote the researchers. [Invest Ophthalmol Vis Sci 2024;doi:10.1167/iovs.65.14.7]

The study involved 11,959 participants (mean age, 7.55 years; boys, 52.2 percent) who received comprehensive ophthalmic examinations and retinal photography, and whose involvement in physical activity was obtained from validated questionnaires. Physical activity was defined as outdoor and indoor exercise as well as outdoor leisure activities, whereas physical inactivity included watching television, playing video games, doing homework, reading, using a computer, and using other electronic devices. Participants engaged in physical inactivity for a mean of 18.74 hours/week and were physically inactive for a mean of 38.82 hours/week.

“To reflect the overall activity level of children more comprehensively, we calculated the ratio of physical activity to inactivity by dividing the total duration of physical activity by that of physical inactivity,” explained the researchers.

Central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were measured from retinal photographs using DLS. “Being noninvasive and relatively accessible, retinal photography has been frequently investigated for CV disease monitoring, screening and prevention in adults,” noted the researchers. [Circ Cardiovasc Imaging 2008;1:156-161]

The mean CRVE was 215.7 μm and mean CRAE was 151.6 μm. After adjusting for sex, age, fellow vessel caliber, right eye axial length, weight, height, mean arterial pressure, and family income, participants with increased ratio of physical activity to inactivity had significantly wider CRAE (β=1.033; p=0.007) and significantly narrower CRVE (β=-2.079; p<0.001), while physical inactivity alone was not found to have significant associations with CRAE and CRVE. Subgroup analysis showed that increased ratio of physical activity to inactivity was associated with wider CRAE and narrower CRVE in boys, and with narrower CRVE (but not wider CRAE) in girls.

“In adults, it has been suggested that changes in CRAE and CRVE can be incorporated into existing prediction scores or used independently to predict CV diseases. Therefore, a similar prediction score may also be developed for children,” suggested the researchers. [Br J Ophthalmol 2022;106:1722-1729]

“We demonstrated that increased physical activity in children is associated with healthier microvasculature, characterized by wider retinal arterioles and narrower venules. This finding contributes to the growing evidence that physical activity positively influences vascular health from a young age,” they concluded.