Night work is related to higher global and central adiposity in Brazil: National Health Survey, 2013

BACKGROUND: Night work can disturb the natural circadian rhythm, leading to disruptions in metabolic rate and subsequent overall gain weight or even more harmful abdominal adiposity. Our aims were to investigate the associations between night work frequency and markers of overall and central obesity. METHODS: We conducted a cross-sectional analysis of data from the Brazilian National Health Survey on over 35 500 current workers. Exposure to current night work was composed of three categories: daytime work (reference category), less than one night per week, and more than two nights per week. The body mass index and waist circumference were used as adiposity markers. Logistic and multinomial regression models were used, with adjustment for demographic characteristics, work conditions, self-related health, and health-related behaviors. RESULTS: After complete adjustment, individuals who worked two or more nights a week had higher odds of overweight (odds ratio [OR]: 1.20, 95% CI: 1.04-1.38), obesity (OR: 1.38, 95% CI: 1.17-1.64) and increased waist circumference (OR: 1.27, 95% CI: 1.10-1.46) than daytime workers. CONCLUSIONS: Night work was significantly associated with measures of adiposity. Changes in working conditions, such as controlling the numbers of nights worked per week or promoting workplaces with healthy meals and the opportunity to perform physical exercise at work, could be suggested.