Warning for Teenage Boys---Stay Away From Computers and TVs

Television, Computer Viewing of More Than 2 Hours per Day May Increase Metabolic Syndrome Risk in Teenage Boys

Teenage boys with screen time (ST) of 2 or more hours per day are at greater risk for insulin resistance and other markers of metabolic syndrome, according to the results of a cross-sectional analysis reported in the July issue of the Archives of Pediatrics & Adolescent Medicine.

"Of all sedentary activities, [ST] (ie, watching television/DVDs/videos and computer use) is the most popular, with reports that the majority of Australian, European, and North American teenagers spend more than 2 hours per day in front of screens," write Louise L. Hardy, PhD, MPH(Hons), from the University of Sydney in Sydney, Australia, and colleagues. "Among children, ST is associated with the development of obesity and poor dietary habits. In adults, there is strong evidence that prolonged ST (television viewing in particular) is independently associated with biomarkers of metabolic and cardiovascular disease, but only a few studies have examined the association between ST and metabolic risk among children and adolescents and the findings of these studies are mixed."

The goal of the study was to evaluate the association in mid-adolescence between ST guidelines and risk factors for cardiovascular disease, type 2 diabetes mellitus, and fatty liver diseases. At high schools in Sydney, Australia, 496 grade 10 students underwent measurement of body mass index, waist circumference, cardiorespiratory endurance, dietary factors, socioeconomic factors, and pubertal status. Mean age was 15.4 ± 0.4 years; 58% were boys.

The investigators calculated ST for weekday, weekend, and the entire week and categorized ST as less than 2 hours per day or 2 or more hours per day. Outcomes included blood pressure; fasting blood levels of high-density lipoprotein and low-density lipoprotein cholesterol, triglycerides, insulin, and glucose; homeostasis model assessment of insulin resistance (HOMA-IR); and blood levels of alanine aminotransferase, gamma-glutamyltransferase, and high-sensitivity C-reactive protein.

For all students, mean ST was 3.1 hours per day for the week, 2.6 hours per weekday, and 4.4 hours per weekend day. Compared with girls, boys were more likely to exceed ST guidelines (odds ratio [OR], 2.71; 95% confidence interval [CI], 1.67 - 4.38). Among girls, ST guidelines were not significantly associated with metabolic risk factors.

Unadjusted ORs demonstrated that in boys, not girls, exceeding ST guidelines on weekdays was significantly associated with abnormal levels of insulin (OR, 1.88; 95% CI, 1.09 - 3.22), HOMA-IR (OR, 1.97; 95% CI, 1.12 - 3.48), levels of high-sensitivity C-reactive protein (OR, 2.94; 95% CI, 1.12 - 7.70), and diastolic blood pressure (OR, 3.30; 95% CI, 1.35 - 8.12).

After adjustment for potential confounders, boys who exceeded ST guidelines on weekdays were more likely to have elevated HOMA-IR (adjusted OR, 2.42; 95% CI, 1.11 - 5.28) and insulin levels (adjusted OR, 2.73; 95% CI, 1.43 - 5.23).

"Adolescent boys with ST of 2 or more hours per day on weekdays have twice the risk of abnormal levels of insulin and HOMA-IR compared with peers with ST less than 2 hours per day on weekdays," the study authors write. "These results suggest there is an increased risk of insulin resistance among adolescent boys who do not meet ST guidelines on weekdays."

Limitations of this study include cross-sectional design, precluding any causal inference; low response rate (56%); self-report of ST and diet; and difficulty selecting cutoff points for biomarker risk factors.

"Future research needs to determine how much (or how little) sitting time constitutes health risk among young people," the study authors conclude. "The findings support interventions that promote the ST guideline and encourage young people to reduce excessive ST, especially during the week when they have spent the majority of their day sitting in class. Screen time is a modifiable behavior and interventions to reduce the recreational use of small screens during weekdays may help reduce the risk of progression of insulin resistance to type 2 diabetes."

One of the study authors was employed by the New South Wales (NSW) Department of Health on the NSW Biostatistical Officer Training Program. The Physical Activity and Nutrition Survey 2004 was funded by the NSW Department of Health.

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