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• Posted September 15, 2025

Smoking Increases Risk Of Type 2 Diabetes

Smokers have a higher risk of developing type 2 diabetes, especially if they are genetically predisposed to the condition, a new study says.

People who ever smoked at all have an elevated risk of all four subtypes of type 2 diabetes, and heavy smokers are at even greater risk, researchers reported Saturday at a meeting of the European Association for the Study of Diabetes in Vienna.

“It is clear that smoking increases the risk of type 2 diabetes whatever the subtype — that is, regardless of whether the diabetes is characterized by insulin resistance, lack of insulin, obesity or old age,” lead researcher Emmy Keysendal, a doctoral student at the Karolinska Institute in Stockholm, said in a news release.

For the study, researchers analyzed data from 3,325 people with type 2 diabetes and 3,897 healthy folks participating in diabetes studies in Norway and Sweden.

People who had ever smoked were more than twice as likely as never-smokers to develop severe insulin-resistant diabetes (SIRD), characterized by an inability to efficiently use insulin to turn blood sugar into energy, results show.

Ever-smokers also had a:

• 20% increased risk for severe insulin-dependent diabetes (SIDD), characterized by a lack of insulin.

• 29% increased risk for mild obesity-related diabetes (MOD), associated with obesity.

• 27% increased risk for mild age-related diabetes (MARD), associated with aging.

Heavy smoking caused even higher risks: Nearly 2.4 times for SIRD; 52% for SIDD; 57% for MOD; and 45% for MARD, researchers said. The team defined heavy smoking as 20 cigarettes a day for 15 years.

Overall, smoking was estimated to be responsible for more than a third of insulin-resistant type 2 diabetes cases, researchers said.

“The strongest association was seen for the subtype characterized by severe insulin resistance (SIRD), which suggests that smoking may contribute to diabetes by impairing the body’s ability to respond to insulin,” Keysendal said.

Results also showed that people with a high genetic risk for impaired insulin secretion were more than three times as likely to develop SIRD.

“Our findings emphasize the importance of smoking cessation in the prevention of type 2 diabetes,” Keysendal said. “They also indicate that genetic information may help identify individuals most likely to benefit from extra support in stopping smoking.”

Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.

More information

The U.S. Centers for Disease Control and Prevention has more on smoking and type 2 diabetes.

SOURCE: European Association for the Study of Diabetes, news release, Sept. 13, 2025