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More sitting time at work contributes to weight gain
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Longer sitting time at work was significantly associated with higher BMI for U.S. adults, according to research in the American Journal of Preventive Medicine.
Tin-chi Lin, PhD, of the Center for Injury Epidemiology at the Liberty Mutual Research Institute for Safety in Hopkinton, Massachusetts, and colleagues analyzed data from 5,285 adults aged 38 to 45 years (46.7% women; mean age, 41.5 years; 13.4% black; mean BMI, 27.7 kg/m²) participating in the ongoing National Longitudinal Survey of Youth 1979 (NLSY79) between 2002 and 2010. Participants self-reported height, weight and occupation biannually; survey response rate was 80.3% in 2002 and 80.6% in 2010. Researchers used data from the Occupational Information Network, a comprehensive occupation description database developed for the U.S. Department of Labor, to measure time spent sitting at work, which was measured as “never” (1), “less than half of the time” (2), “about half of the time” (3), “more than half of the time” (4) and “continuously or almost continuously” (5). Those data were then linked to the participants’ survey data. Researchers used fixed-effects longitudinal models to examine the associations between sitting time and BMI and random-effects models to investigate the potential interaction effects between sex and sitting time on BMI.
In fixed-effects models, researchers found that longer sitting time at work was associated with higher BMI for the overall sample (P < .05), but results varied when broken down by sex. The association was statistically significant for men only (P < .01).
The random-effects model showed similar results and indicated that sex and sitting time interacted in their relationship with BMI for men (P < .05), but not for women (P = .82).
“For the present study, the difference in coefficient estimates is not believed to suggest distinct biological mechanisms between men and women, but rather potential residual confounding and selection bias,” the researchers wrote. “The NLSY79 did not comprehensively document participants [physical activity] and did not record participants’ diet. These unmeasured factors may differ between men and women, which may have contributed to the observed gender difference.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
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