compared to non-persistent rotatingshift workers without elevated serum alanine aminotransferase. In contrast, a study of police officers did not find that those who mainlyworked midnight shifts had a higher risk of metabolic syndrome than those who mainly worked day shifts [51]. Because the day shifts started in the early morning (4:00 am) at the research site, this study may not be directly comparable with studies in which the reference group was dayshift workers with a more typical daytime work schedule.