New research suggests that smokers and people regularly exposed to secondhand smoke are more likely to develop type 2 diabetes compared with people who never smoked.

An international team of researchers found that the increased risk of developing type 2 diabetes was 21, 34, and 57 percent for light, moderate, and heavy smokers, respectively, compared with never smokers. They also found secondhand smokers had a 22 percent increased risk for the disease, The Guardian reported.

"Cigarette smoking should be considered as a key modifiable risk factor for diabetes. Public health efforts to reduce smoking will have a substantial impact on the global burden of type 2 diabetes," Frank Hu, co-author of the study, said in a statement.

For the study, researchers conducted a meta-analysis of 88 previous studies on the association between smoking and type 2 diabetes risk, looking at health data from nearly 6 million study participants.

Researchers found that when compared with people who never smoked, current smoking increased the risk of type 2 diabetes by 37 percent; former smoking by 14 percent; and passive smoking (breathing in secondhand smoke) by 22 percent, The Independent reported. They also found a 54 percent increased risk of type 2 diabetes in people who quit smoking less than 5 years ago, which fell to 18 percent increased risk after 5 years and 11 percent increased risk more than 10 years after quitting.

"Despite the global efforts to combat the tobacco epidemic, cigarette use remains the leading cause of mortality and morbidity worldwide," An Pan, the first author of the study and professor of epidemiology at School of Public Health, said in a statement. "This study underscores the importance of implementing and enforcing the provisions of the WHO Framework Convention on Tobacco Control. The smoke-free policies can provide protections for non-smokers and may lead to increased successful cessation in smokers."

The findings are detailed in the journal Lancet Diabetes & Endocrinology.