Mixing day and night shifts is associated with a higher risk of type 2 diabetes, according to a study published in the journal PLoS Medicine.

In a study of more than 175,000 women, those who mixed day and night shifts for three to nine years saw a 20 percent rise in diabetes risk; after 10 to 19 years, they had a 40 percent risk and after 20 or more years, they had a 58 percent increased risk in diabetes compared to women who worked just days or just nights.

A lack of physical activity and regular meal times using results from mixed shifts, says lead author An Pan, a research fellow in the Harvard School of Public Health’s department of nutrition.

“We know that a wide range of biological processes are regulated by the circadian rhythms, including sleep-wake cycles, body temperature, energy metabolism, cell cycle and hormone secretion,” Pan explains.

“I think rotating shift work tends to lead to an unhappy lifestyle,” Pan said.