More reasons to get kids playing outside

“Go outside and play” may be a parental refrain heard more often during school holidays, but it's also proving to be a prescription for better health on a number of fronts.

One new analysis of recent studies among children and teens found time spent outdoors is related to a reduced risk for nearsightedness. British researchers last fall reported that for each additional hour a week spent outdoors, the risk of developing nearsightedness dropped about 2 percent.

The eight studies merged into the analysis included more than 10,000 subjects and showed that nearsighted kids spent an average of 3.7 fewer hours a week outdoors than did those with normal or farsighted vision.

The analysis suggests that more exposure to natural light and time spent looking at more distant objects may be key factors.

Kids who regularly participated in outdoor physical activity had retinal arteries an average of 2.2 microns wider than children with the lowest levels of such activity. A micron is one-thousandth of a millimeter.

Narrowing of the retinal arteries is considered a marker for future cardiovascular risk.

The researchers found that the magnitude of narrowing associated with each hour of screen time was similar to a 10-millimeter increase in systolic (beating heart) blood pressure in children.

The study of nearly 1,500 children included both questioning them and their parents about their activities, taking vital signs and taking digital photos of the blood vessels behind the eye.

The children spent an average of just under two hours a day in screen time, and about 36 minutes a day in physical activity. But the most active, with the widest arteries, were active for just over an hour a day; those with the narrowest arteries were active for under a half-hour.