April 21st, 2011
Kids' 'screen time' linked to early markers for cardiovascular disease
Australian researchers found that more sedentary behavior such as “screen time” was associated with an average narrowing of 2.3 microns in the retinal arteriolar caliber. A micron is one thousandth of a millimeter or one-25th of a thousandth of an inch.
In the study, 6- to 7-year-olds who regularly participated in outdoor physical activity had 2.2 microns wider average retinal arteriolar compared to those children with the lowest level of activity.
The magnitude of the narrowing associated with each hour of television/computer viewing was similar to that associated with 10 millimeters of mercury (mm HG) increase in systolic blood pressure in children, researchers said.
“We found that children with a high level of physical activity had a more beneficial microvascular profile compared to those with the lowest levels of physical activity,” said Bamini Gopinath, Ph.D., lead author and senior research fellow at the Center for Vision Research at the University of Sydney. “This suggests that unhealthy lifestyle factors may influence microcirculation early in life and increase the risk of cardiovascular disease and hypertension later in life.”
Retinal microvascular caliber is a marker for cardiovascular disease and high blood pressure in adults. But this is the first time that a sedentary lifestyle in childhood showed a narrowing of the vessels in the retina that could be a subclinical marker for cardiovascular disease in the future.
The study included 1,492 children in 34 primary schools in Sydney, Australia. Parents answered a 193-item questionnaire, providing the number of hours spent each week in indoor and outdoor physical activity and sedentary activity such as watching television, videogames, computer time and reading.
Researchers took digital photographs of the vasculature in the back of each child’s eye, then calculated average retinal vascular calibers. Height, weight, body mass index (BMI) and three separate blood pressure measurements were taken and averaged.