Medics, police officers and fire fighters could be at increased risk of developing diabetes, experts have said after new research linked s hift work to a heightened risk of being diagnosed with the condition.
Compared to normal office hours, working shifts carries a 9% higher risk of developing diabetes, the study found.
Previous research has linked shift work to weight gain and increased appetite - both of which are risk factors for diabetes, the authors said.
The risk appears to be highest among men and those who work rotating shift patterns, according to the study published in the journal Occupational and Environmental Medicine.
Researchers examined 12 studies involving more than 225,000 people, of whom almost 15,000 had diabetes.
While the overall risk of developing diabetes was 9% among shift workers, the authors found that m en who worked shifts were 37% more likely to develop the condition.
And those who worked rotating shift patterns, in which they worked different parts of the 24 hour cycle on a regular basis, had a 42% higher risk than those who worked a fixed shift pattern, they said.
Previous studies have linked shift work to a variety of health problems including digestive problems, some cancers and heart issues but this is the first study which links diabetes to the occupations which require abnormal working hours.
"Shift work is associated with a significantly increased risk of diabetes mellitus (DM), especially in men and groups with rotating shifts," researchers said.
"Given the increasing prevalence of shift work worldwide and the heavy economic burden of DM, the results of our study provide practical and valuable clues for the prevention of DM and a study of its aetiology."
Commenting on the research, P rofessor Nick Wareham, director of the Medical Research Council Epidemiology Unit at the University of Cambridge, said: "This new meta-analysis provides a useful summary across previously published studies of the magnitude of the link between shift working and type 2 diabetes.
"It suggests that there may be a moderately sized link, which is slightly stronger in men.
"The study can't exclude the possibility that the results are explained by other risk factors for diabetes that are also linked to shift working.
"If it were shown that it is shift working itself that has a link to diabetes, then the key question would be to identify what interventions could be put in place to alleviate the risks in those who have to work shifts."
In the UK, around 2.9 million people have diabetes, with around 90% of cases being type 2.
There are also thought to be around 850,000 people with undiagnosed diabetes.
Dr Alasdair Rankin, director of research at charity Diabetes UK, said: "This study combines evidence from previous research to suggest people who do lots of shift work may be at increased risk of type 2 diabetes, especially for men and people who work rotating shifts.
"The exact reasons for this are unclear and the evidence that it is the shift work that is causing an increase to risk of type 2 diabetes is not conclusive. Nonetheless, these findings suggest that shift workers need to be aware of their personal risk of developing type 2 diabetes.
"They can do this by taking a type 2 diabetes risk assessment, either online or in their local pharmacy. The best way to reduce your risk of type 2 is to maintain a healthy weight through regular physical activity and by eating a healthy balanced diet."