Diabetes risk linked to quitting smoking fades over time
The risk ratio for diabetes in people who quit relative to persistent smokers was 1.15 at 3 years and 0.95 at 15 years.
Our read
Populations- Studied:
- Cohort study of 52,880 Japanese employees aged 40 years or older, against persistent smokers
- What changed:
- Diabetes risk was higher at 3 years (risk ratio 1.15) but did not differ at 15 years (0.95) against persistent smokers
- The catch:
- The cohort included only Japanese employees aged 40 and older
- In the record:
- The 136th paper on smoking cessation with results in people; 351 on record in all.
- Why it’s aging research:
- A leading disease of aging, its risks or menopause.
Editor of record: Boris Djordjevic · AgingResearch.News
An observational study tracked 52,880 Japanese employees aged 40 years or older who were currently smoking and free of diabetes. Researchers analyzed annual health checkup data collected between 2008 and 2022 using a sequential-cohort target trial emulation. Across the sequential cohorts, 331,701 enrollments were followed, with a mean age of 49.1 years, and 25,749 individuals developed diabetes.
Smoking cessation was associated with a diabetes risk ratio of 1.15 at 3 years relative to persistent smoking. By 15 years, the risk ratio was 0.95, and the range of likely values included no difference. The authors observed that the initial excess risk diminished over time, leaving no long-term increase in diabetes risk.
Why it matters
Diabetes is a common metabolic disease that becomes more frequent with advancing age. Clarifying how quitting smoking affects long-term metabolic health helps address concerns that temporary post-cessation weight gain leads to lasting harm.
Caveats
Because this was an observational study based on routine health checkup data rather than a randomized trial, unmeasured confounding may still affect the results. The cohort included only Japanese employees aged 40 and older who smoked, so the findings may not apply to younger adults or other populations.
The paper
Preventive Effect of Smoking Cessation on Diabetes Onset: A Target Trial Emulation Approach
Kyoto Prefectural University of Medicine
Diabetes, Obesity & Metabolism, Oct 25, 2026
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