Doing shift work can increase your risk of developing diabetes, according to new research.

Researchers in China found that any period of shift work was associated with a 9% greater risk of developing  type 2 diabetes compared with working normal office hours. And the risk is highest in men and in people working rotating shifts.

Researchers looked at 12 international studies involving more than 226,500 people, of whom 14,600 had diabetes.

The study authors found after further analysis that the heightened risk for shift workers rose to 37% for men.

The reasons for this finding were not clear, but suggested that men working shifts may need to pay more attention to the possible health consequences of this type of work, the authors say.

Daytime levels of the male hormone testosterone are controlled by the internal body clock, so it is possible that repeated disruption in sleep patterns may affect this, say the authors, pointing to research implicating low male hormone levels in diabetes.

Most shift patterns, with the exception of mixed and evening shifts, were associated with an increased risk of diabetes compared with the risk for people working normal office hours.

Rotating shifts, in which people work different parts of the 24-hour work cycle on a regular basis, rather than fixed working hours, were associated with the highest risk, at 42%.

The researchers point out that rotating shifts make it harder for people to adjust to a regular sleep-wake cycle, and some research has suggested that a lack of sleep, or poor quality sleep, may trigger or worsen insulin resistance, which contributes to diabetes.

The research is published in the journal Occupational & Environmental Medicine.