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/m2. 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.