People who do shiftwork are more likely to have a diet that promotes chronic inflammation — which may partly explain the health risks associated with shiftwork, reports a study in the February Journal of Occupational and Environmental Medicine, official publication of the American College of Occupational and Environmental Medicine (ACOEM).

Michael Wirth, MSPH, PhD, of the University of South Carolina, Columbia, and colleagues analyzed the relationship between shiftwork and pro-inflammatory diet using data from a nationwide sample of employed adults. Based on diet questionnaires, the researchers calculated a "dietary inflammatory index" (DII) for each individual. The greater the DII score, the more pro-inflammatory the diet.

With adjustment for other factors, shiftworkers had an elevated DII, compared to day workers. The difference was significant for rotating shiftworkers (those who worked varying shifts): average DII 1.07, compared to 0.86 for day workers.

Women had higher DII values than men. Among women, the DII was higher for evening or night shiftworkers compared to day workers: 1.48 versus 1.17.

Shiftwork has been linked to increased risks of disease, including high blood pressure, obesity, cardiovascular disease, and diabetes. Poor eating habits may contribute to some of these risks. Western-style diets with higher levels of calories and fats have been linked to increased inflammation, compared to Mediterranean diets high in fruits and vegetables.

The DII provides a way of measuring how "pro-inflammatory" a person's diet is. A recent study of police officers found a higher DII in officers doing shiftwork. The new study suggests a similar elevation in DII among shiftworkers in the general population.

It's still unclear how much of an impact the elevated DII would have on health, but a pro-inflammatory diet might be one factor contributing to shiftwork-related health risks. "Inflammatory diets represent a target for behavioral interventions to reduce the health impacts of shiftwork," Dr. Wirth and coauthors write. They add that interventions should address other important lifestyle factors as well, including physical activity, proper sleep, and light exposure.

Citation — Wirth MD, Burch J, Shivappa N, et al. Dietary inflammatory index scores differ by shift work status: NHANES 2005 to 2010. J Occup Environ Med. 2013;56(2):145-8.