Children and adolescents who consistently watch television for two hours or more daily are at an increased risk for obesity, cigarette smoking, and hypercholesterolemia by early adulthood, according to an article in the July 17th issue of The Lancet.

Previous research had identified associations between television viewing and poor health outcomes such as hypercholesterolemia and obesity, but no longitudinal study had assessed these effects into adulthood.

In the current study, Dr. Robert Hancox and his New Zealand colleagues studied around 1000 children born in Dunedin, New Zealand, in 1972-73 who were followed at numerous intervals to age 26 years. During follow-up, parents (for children aged 5-11 years) and adolescents (aged 13 years and over) provided details of the duration of weekly television viewing. Body-mass index, blood pressure, cholesterol concentrations, and cardiovascular fitness were assessed at 26 years of age.

A clear association was found between extensive television viewing (more than two hours a day) among children and adolescents and increased body mass index, elevated cholesterol, greater proportion of smoking, and poor cardiovascular fitness at age 26 years; no association was found between television viewing and blood pressure. These associations remained after adjustment for potential confounding factors such as childhood socioeconomic status, body-mass index at age 5 years, parental body-mass index, parental smoking, and physical activity at age 15 years.

The investigators estimated that among all 26-year-olds, 17% of overweight, 15% of elevated cholesterol, 17% of smoking, and 15% of poor fitness can be attributed to watching television for more than two hours a day during childhood and adolescence.

Hancox commented, “Our results suggest that excessive television viewing in young people is likely to have far-reaching consequences for adult health. We concur with the American Academy of Pediatrics that parents should limit children’s viewing to 1?2 hours per day; in fact, data suggest that less than 1 hour a day would be even better.

Although parents might find this difficult to maintain, lifestyle modifications in adulthood to reverse overweight, poor fitness, high blood cholesterol, and smoking are also notoriously difficult to achieve. Parents will need support and encouragement at an individual, community, and societal level. Adults are likely to obtain health benefits themselves if they lead by example and turn off the television. We believe that reducing television viewing should become a population health priority.”