Sleep deprivation and obesity in shift workers in southern Brazil

Objective: The objective of our study was to explore the association between sleep deprivation and obesity among shift workers. Design: A cross-sectional study was conducted. Obesity was defined as BMI >= 30 kg/m(2). Time of sleep was categorized as: >5 h of continuous sleep/d; <= 5 h of continuous sleep/d with some additional rest ( sleep deprivation level I); and <= 5 h of continuous sleep/d without any additional rest (sleep deprivation level II). Sociodemographic, parental and behavioural variables were evaluated by means of a standardized pre-tested questionnaire. Potential confounding factors were controlled for in the multivariable model. Setting: A poultry-processing plant in southern Brazil. Subjects: Nine hundred and five shift workers (63% female). Results: Obesity was more prevalent in the participants who were female, aged 40 years and older, who had less schooling and reported excess weight in both parents. Sleep deprivation levels I and II were associated with increased income, number of meals consumed throughout the day and nightshift work. All of the workers who exhibited a degree of sleep deprivation worked the night shift. After controlling for potential confounding factors, the prevalence ratios of obesity were 1.4 (95% CI 0.8, 2.2) and 4.4 (95% CI 2.4, 8.0) in the workers with sleep deprivation levels I and II, respectively, compared with the reference group. Conclusions: These results show a strong association between sleep deprivation and obesity in shift workers and that sleep deprivation may be a direct consequence of working at night.