Shift work and serum 25-OH vitamin D status among factory workers in Northern Italy: Cross-sectional study.

Low levels of vitamin D are related to muscle weakness, poor balance, and higher risk of falls, and can therefore have a major impact on performance and safety at work. Little knowledge exists on the association between work environment and vitamin D status. This study evaluates vitamin D status in shift workers. In this cross-sectional study, led during early springtime, 96 male shift workers at an engineering factory in Northern Italy, and 100 male daily workers operating nearby, participated. 25-OH vitamin D concentration, anthropometric indexes, fasting glycemia and triglycerides were detected. 51 shift workers underwent anamnesis collection on lifestyle and habits and determination of heel bone mineral density. Vitamin D levels were lower in shift workers than daily ones (13.4 ± 5.3 ng/mL versus 21.9 ± 10.7 ng/mL, p < 0.001). Linear regression analysis adjusted for age, body mass index and smoking habits confirms a statistically significant association between shift work and vitamin D levels (p < 0.0001). An association trend between cigarette smoking and low vitamin D values was found. No significant association was detected between the heel bone mineral density values and vitamin D levels or smoking habits. In conclusion, this cross-sectional study highlights the high prevalence of vitamin D deficit among shift workers compared with daily ones.