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TV in child’s bedroom an independent risk factor for overweight
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Children who have a television in their bedroom at age 7 years have higher BMI and fat mass index at age 11 years than children with no bedroom television, according to study findings published in the International Journal of Obesity.
“Ironically, while our screens have become flatter, our children have become fatter,” Anja Heilmann, PhD, MSc, FHEA, a clinical lecturer in dental public health at University College London, and colleagues wrote. “Indeed, a relationship between TV viewing and overweight among children and adolescents has been repeatedly reported. There is some evidence that a TV in the child’s bedroom might exacerbate the problem.”
Heilmann and colleagues analyzed data from 12,556 children from wave 5 of the UK Millennium Cohort Study, a prospective cohort study following children born between September 2000 and January 2002 (6,353 boys). Researchers followed children from age 7 years to age 11 years, assessing measurements of height, weight and body fat collected by interviewers, as well as data collected during wave 4 (age 7 years) on screen-based media use; questions included whether the child had a television in the bedroom. Researchers also assessed bedtime and physical activity data at age 7 years as potential mediating variables. Primary outcome was associations between screen-based media use and adiposity at age 11 years, measured via BMI, fat mass index (FMI) and overweight.
Within the cohort, mean BMI at age 11 years was 19 kg/m² for boys and 19.5 kg/m² for girls; mean FMI was 4.1 kg/m² for boys and 5 kg/m² for girls; 25% of boys and 30% of girls had overweight at age 11 years. At age 7 years, 55% of boys and 53% of girls had a television in their bedroom.
Researchers found that having a bedroom TV at age 7 years was associated with a mean 0.29 kg/m² higher BMI for boys (95% CI, 0.06-0.52) and a mean 0.57 kg/m² higher BMI for girls (95% CI, 0.31-0.84), as well as a mean 0.2 kg/m² higher FMI for boys (95% CI, 0.04-0.37) and a mean 0.39 kg/m² higher FMI for girls (95% CI, 0.21-0.57). Results persisted after adjustment for BMI at age 3 years, breast-feeding duration, race, maternal BMI at wave 2, maternal education at wave 5 and family income at wave 5, as well as further adjustment for bedtime and physical activity level at age 7 years.
Compared with children aged 11 years who had no television in the bedroom, both boys and girls aged 11 years with a bedroom television had an increased relative risk for overweight (RR for boys = 1.21, 95% CI 1.07-1.36; RR for girls = 1.31, 95% CI 1.15-1.48).
Hours spent watching TV or DVDs were associated with increased risk for overweight among girls only, according to researchers. Researchers did not observe any associations between body fat and computer use at age 7 years.
“After extensive adjustment for a wide range of covariates, all three measures of body fatness we assessed were associated with having a TV in the child’s bedroom,” the researchers wrote. “Girls who had a TV in their bedroom at age 7 [years] were at an approximately 30% higher risk of being overweight at age 11 [years] compared to those who did not have a TV in their bedroom, and for boys the risk was increased by about 20%. The effect size of this increased risk of being overweight is comparable to the risks previously identified for physical inactivity and not having been breast-fed.”
The researchers noted that future childhood obesity prevention strategies should consider access to television in the child’s bedroom. – by Regina Schaffer
Disclosure: One of the study authors reports receiving a grant from the UK Economic and Social Research Council.
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