Smoking fuels all types of type-2 diabetes, new study warns

Italy, Sep 15, 2025 — India already faces a surging type-2 diabetes (T2D) crisis, with over 100 million people affected and numbers still climbing. New research from Karolinska Institutet, Sweden, presented at the European Association for the Study of Diabetes (EASD) 2025, reveals smoking sharply raises the risk for every major T2D subtype—including severe insulin-resistant and insulin-deficient forms—sending a clear warning to India, where tobacco use remains widespread.

Key findings on diabetes subtypes and smoking risk

Scientists tracked 3,325 patients across two long-term Nordic cohort studies—the HUNT Study in Norway and the ESTRID Study in Sweden—and classified diabetes into four subtypes:

• Severe Insulin-Resistant Diabetes (SIRD)

• Severe Insulin-Deficient Diabetes (SIDD)

• Mild Obesity-Related Diabetes (MOD)

• Mild Age-Related Diabetes (MARD)

Compared to never-smokers, ever-smokers showed significantly higher risks across all subtypes:

• SIRD: approximately 2.15 times greater risk

• SIDD: 20% higher

• MOD: 29% higher

• MARD: 27% higher

Among heavy smokers (around 15 pack-years), risks rose even more dramatically:

• SIRD risk increased 2.35-fold

• SIDD, MOD, and MARD risks climbed between 45% and 57%

Moreover, a combined genetic risk for poor insulin secretion further compounded the danger. Heavy smokers with this genetic predisposition faced 3.5 times the SIRD risk.

Expert perspectives on study implications

Dr. Mikael Svensson, a diabetes researcher not involved in the study, commented, “This research importantly highlights that tobacco use is a potent driver across the full spectrum of type-2 diabetes subtypes, not just typical obesity-related diabetes. The increased risks for severe insulin resistance and insulin deficiency underscore smoking’s systemic impact on glucose metabolism and pancreatic function.”

Dr. Navneet Agrawal, a noted diabetologist from India, emphasized the local ramifications: “India’s high tobacco consumption—be it cigarettes, bidis, or smokeless products like gutkha—coupled with a genetic predisposition to diabetes, makes smoking cessation a crucial intervention. This study strengthens the case for integrating tobacco control fully into diabetes prevention strategies in the country.”

Context and background

Type-2 diabetes is a complex disease with growing global incidence. India alone has over 100 million diagnosed cases, making it one of the largest affected populations worldwide. The disease is heterogeneous, with varying pathophysiological mechanisms—some patients have predominant insulin resistance, while others suffer from insulin deficiency. These differences affect disease severity, complication risks, and treatment response.

Smoking has long been recognized as a risk factor for T2D, causing oxidative stress, systemic inflammation, and endothelial dysfunction that impair insulin action and beta-cell function. Previous epidemiological studies showed smokers have a 20-40% elevated risk of developing T2D; quitting smoking reduces risk by up to 40% over time.

This new study adds nuance by linking smoking to each T2D subtype, especially highlighting the heightened risk for the severe insulin-resistant form (SIRD). It also extends concern beyond traditional cigarette smoking to include all forms of tobacco, which is critical in countries like India where smokeless tobacco use is common.

Public health implications for India

India’s diabetes epidemic is fueled by urbanization, dietary shifts, sedentary lifestyles, and genetic susceptibility. The pervasive tobacco use aggravates this crisis. The study’s findings call for urgent and multi-pronged public health actions:

• Smoking cessation: Promote counseling, nicotine-replacement therapies, and community programs tailored to local tobacco habits.

• Ban and reduce smokeless tobacco: Enforce strict regulations against gutkha, khaini, and similar products.

• Early screening: Widespread fasting glucose and HbA1c tests, especially for high-risk populations with family history or tobacco exposure.

• Lifestyle interventions: Encourage balanced nutrition, regular physical activity, and weight management to moderate genetic risks.

Experts agree that tobacco control policies should be integrated closely with diabetes prevention efforts rather than addressed separately. Reducing tobacco use not only cuts cancer and cardiovascular disease burden but also directly curbs the diverse forms of T2D, saving millions from severe complications.

Balanced perspective and limitations

While the study illuminates critical links, it is observational and cannot confirm causation. Residual confounding factors—such as diet, environmental exposures, and precise measures of tobacco consumption—may influence results. Genetic risk was assessed through common markers but does not capture all hereditary factors.

Further research is needed to explore the biological mechanisms by which smoking specifically affects insulin function across different diabetes subtypes and to test interventions targeting tobacco use in diverse populations.

Practical takeaways for readers

For individuals, the message is unequivocal:

• Quitting tobacco now significantly reduces type-2 diabetes risk.

• Avoiding all forms of tobacco—including smokeless variants—is essential.

• Regular health check-ups can detect diabetes early, improving outcomes.

• Combined with healthy habits, quitting smoking has immense benefits beyond just lungs or heart health.

Medical Disclaimer

This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.

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