Smoking is well known to harm health in many ways, and new research has now confirmed that it also increases the risk of type 2 diabetes—no matter what kind of diabetes a person develops.
At the annual meeting of the European Association for the Study of Diabetes (EASD) in Vienna, scientists from Sweden, Norway, and Finland presented findings showing that smoking raises the risk of all four recognized subtypes of type 2 diabetes.
These subtypes are:
- SIRD (severe insulin-resistant diabetes), where the body cannot respond properly to insulin.
- SIDD (severe insulin-deficient diabetes), where the body does not produce enough insulin.
- MOD (mild obesity-related diabetes), usually linked to younger age and obesity.
- MARD (mild age-related diabetes), which tends to develop later in life.
Type 2 diabetes does not look the same in everyone, and these categories help explain the different ways the disease can affect people.
But until now, it was unclear if smoking played a different role in each subtype.
The research team studied data from nearly 3,400 people with type 2 diabetes and almost 3,900 people without the disease.
They found that people who had ever smoked—whether currently or in the past—were more likely to develop all four subtypes than people who never smoked. The strongest link was with SIRD, the insulin-resistant form.
Smokers were more than twice as likely to develop SIRD compared to non-smokers. For the other subtypes, smoking raised the risk by about 20–30%. The researchers estimated that more than a third of SIRD cases were caused by smoking.
Heavy smoking (defined as the equivalent of smoking a pack of cigarettes a day for 15 years or more) made the risk even higher. Heavy smokers were more than twice as likely to develop SIRD and about 45–57% more likely to develop the other three subtypes.
Interestingly, in Sweden, the researchers also found that heavy use of snus, a smokeless tobacco product common in Scandinavia, was linked to a higher risk of the severe subtypes SIRD and SIDD.
The team also looked at whether genetics made a difference. People with a genetic risk for type 2 diabetes or poor insulin production were especially vulnerable if they smoked heavily. For example, heavy smokers with a genetic risk for reduced insulin production were more than three times as likely to develop SIRD compared to people without those risks.
Lead researcher Emmy Keysendal of Karolinska Institutet in Stockholm said the findings highlight the urgent need for smoking prevention and support for quitting.
“It is clear that smoking increases the risk of type 2 diabetes, whatever the subtype,” she explained. “The strongest association was for severe insulin resistance, suggesting smoking may damage the body’s ability to respond to insulin.”
This research adds to the evidence that quitting smoking not only protects the heart and lungs, but also helps reduce the risk of developing diabetes in any form.
