Published on 23 September 2015

Healthcare professionals are reminding people that stopping smoking could reduce the risk of developing type 2 diabetes, following a recent study that suggested there could be a link.

And it is not just people who smoke that are at risk, as the possibility of developing type 2 diabetes for people who have never smoked, but have been exposed to second-hand smoke, could be up by more than a fifth.

Passive smokers could be at a 22% higher risk of developing type 2 diabetes than non-smokers, according to the results of a study in China, recently published in The Lancet.

Stopping smoking can prevent a number of health problems, including type 2 diabetes

Researchers based their findings on figures from 6 million people, taking account of many known contributory risk factors for type 2 diabetes, including diet and physical activity. The results for passive smokers came from around 150,000 people. 

The diabetes risk increase varied depending on how much somebody smoked and the length of time a person had quit.

Of those studied 295,446 developed type 2 diabetes and where possible the researchers used the findings to create summary estimates of how different smoking behaviour was linked to the risk of developing type 2 diabetes.

Among the results included that current smokers were 27% more likely to develop type 2 diabetes than current non-smokers. Former smokers were 14% more likely to develop type 2 diabetes than those who had never smoked, while those who had never smoked, but had been exposed to passive smoke, were 22% more likely to develop type 2 diabetes than those who had never smoked.

The researchers said: “Active and passive smoking are associated with significantly increased risks of type 2 diabetes. The risk of diabetes is increased in new quitters, but decreases substantially as the time since quitting increases. If the association between smoking and risk of type 2 diabetes is causal, public health efforts to reduce smoking could have a substantial effect on the worldwide burden of type 2 diabetes.”

The risk of developing type 2 diabetes also started to decrease in proportion to the time since a person stopped smoking.

An NHS Choices Behind the Headlines analysis of the study said: “The results were consistent and the increases in diabetes risk linked to smoking varied in line with smoking intensity and length of time a person had quit. While prospective studies cannot prove cause and effect, these findings do hint at one. A randomised control trial would be needed to know for sure, but is not feasible, as it would be unethical to allocate people to smoke, due to its known health effects.

“Though the link appears clear for passive smoke exposure, it is also worth noting that self-reported passive smoke exposure could have covered various intensities of smoke exposure. This result was based on seven studies - three from the US, two from Europe, one from Korea and one from Japan. The specific questioning to establish passive smoking status is not reported. For example, some people could have meant they have been extensively exposed to smoke in their homes throughout their lives, while others could just have been referring to being exposed to passive smoke in public places occasionally. Therefore, although the link seems clear, the 22% increased risk estimate may be imprecise and could not easily be applied to particular individuals with passive smoke exposure.

“Overall, the study confirms the well-established fact that exposure to tobacco smoke - either active or passive - is harmful to health.”  

Stoptober campaign

Giving up smoking, if you smoke, is one of the biggest steps you can take to improve your health. 

Search ‘Stoptober’ online to sign up for the Stoptober challenge. The Department of Health Stoptober campaign encourages people across the country to stop smoking together on the 1st October for 28 days (and beyond). Stop smoking for 28 days and you are five times more likely to stop for good.

To find your local NHS Stop Smoking Service visit: or call 0300 123 1044.
Read 10 health benefits of stopping smoking here
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Find out more about DRWF-funded research here
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Read DRWF diabetes information leaflets here
Join the Diabetes Wellness Network here

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