24-hour work shifts, sedentary work, and obesity in male firefighters.

Background Little is known about the occupational risk factors for obesity in US firefighters. Methods 308 male California firefighters, who participated in a work and obesity project, were chosen. Working conditions were measured with a firefighter-specific occupational health questionnaire. Adiposity was clinically assessed using body mass index (BMI), waist circumference (WC), and body fat percent. Results In a multivariate analysis, the prevalence of obesity by all measures was significantly higher (PRs = 3.69-6.03, P < 0.05) in the firefighters who reported seventeen to twenty-one shifts than those who reported eight to eleven shifts in the past month. Prolonged sedentary work was also a risk factor for obesity by BMI (PR = 4.18, P < 0.05). Furthermore, there was a linear dose-response relationship of obesity by BMI and WC with the number of 24-hr shifts and sedentary work. Conclusions Many additional 24-hr shifts and prolonged sedentary work substantially increased the risk for obesity in male firefighters. (C) 2016 Wiley Periodicals, Inc.