Shift work in association with abdominal fat areas, body mass index, and metabolic syndrome: The hitachi health study

The relationship between shift work and abdominal fat distribution has not been well investigated. This study assessed the association between shift work and visceral fat area (VFA), subcutaneous fat area (SFA), waist circumference (WC), body mass index (BMI), and metabolic syndrome (MS) among 5,745 men and 682 women aged 30 to 75 years who underwent an abdominal computed-tomography (CT) scanning examination in a comprehensive health checkup. Analyses of covariance and multiple logistic regression analyses were conducted. In fully adjusted model, men working in rotating shift had the highest mean of VFA followed by men working in nighttime and daytime shift (126.5 cm2, 121.1 cm2, and 117.7 cm2, respectively). Similarly, men working in rotating shift had the highest mean of WC followed by men working in nighttime and daytime shift (86.9 cm, 86.5 cm, and 85.8 cm, respectively). However, men working in daytime shift had the highest mean of SFA compared to men working in nighttime and rotating shift after adjustment for VFA (140.6 cm2, 138.2 cm2, 135.7 cm2, respectively). After additional adjustment for SFA, women working in rotating shift had the highest mean of VFA followed by women working in nighttime and daytime shift (88.4 cm2, 86.1 cm2, and 81.0 cm2, respectively). Shift work was not significantly associated with BMI and MS either in men or women. Shift work is a risk factor for elevated abdominal fat mass. Men working in rotating shift appear to be the most vulnerable group compared to men working in daytime and nighttime shift.