Miriam E. Tucker
August 17, 2018
The weight gain that often accompanies smoking cessation temporarily raises the risk for developing type 2 diabetes, but it doesn't diminish the overall benefits in reducing cardiovascular and all-cause mortality, new research shows.
The findings, from three large US cohort studies of healthcare professionals, were published online August 15 in the New England Journal of Medicine by doctoral student Yang Hu, SM, from the departments of nutrition and epidemiology at Harvard T.H. Chan School of Public Health, Boston, Massachusetts, and colleagues.
Among more than 150,000 total participants from the longitudinal Nurses' Health Study, the Nurses' Health Study II, and the Health Professionals Follow-up Study, those who stopped smoking and then gained weight had an increased risk for developing type 2 diabetes for about 5 to 7 years compared with those who continued smoking, but the risk dropped after that.
In contrast, significant reductions in both cardiovascular and all-cause mortality compared with current smokers occurred throughout the same time period, even among those who gained weight.
"It's been known that quitters may have an elevated risk of developing diabetes or worsening glucose tolerance in the first few years after quitting, and this may discourage smokers from quitting, but our study shows that it is the weight change after quitting that determines diabetes risk — so as long as quitters minimize their weight gain, their diabetes risk will not increase and, over the long run, is reduced," said senior author Qi Sun, associate professor in the Department of Nutrition at Chan, in a statement from Harvard.
Benefits of Quitting Far Outweigh Risks: Action Still Needed on Smoking
In an accompanying editorial, Steven A. Schroeder, MD, from the Department of Medicine, University of California, San Francisco, writes: "For clinicians, the main message from the article by Hu et al. is that the cardiovascular and overall mortality benefits of stopping smoking far outweigh the risks of acquiring type 2 diabetes."
However, Schroeder cautions, "the participants in the three cohorts, all health professionals, had health risks and behaviors that did not mirror those of smokers in 2018, who tend to be concentrated among vulnerable populations."
And he points out that although the current US smoking prevalence is at a provisional low of 13.9%, that still leaves 37 million current smokers.
"Much greater reduction in smoking prevalence is possible. That laudable goal deserves aggressive action."
Diabetes Risk After Smoking Cessation in Those Who Gain Weight
From the three large databases, 162,807 participants without diabetes, cardiovascular disease, or cancer at baseline were analyzed. During a mean of 19.6 years of follow-up, 12,384 were diagnosed with type 2 diabetes.
Overall, recent quitters — those with 2 to 6 consecutive years since smoking cessation — had a higher risk for developing type 2 diabetes than did current smokers.
When analyzed by degree of weight gain, those who didn't gain any weight after quitting did not have a greater diabetes risk than did current smokers (hazard ratio [HR], 1.08; not significant). The increased risk was also nonsignificant (HR, 1.15) for those who gained just 0.1 to 5.0 kg (0.2 to 11 lbs).
In contrast, those who gained more than 5.0 kg had significantly increased risks for developing diabetes, with HRs of 1.36 among those gaining 5.1 to 10.0 kg and 1.59 among those gaining more than 10.0 kg.
However, the risk peaked at 5 to 7 years after quitting and then gradually decreased.
Mortality Benefits of Smoking Cessation Maintained
The mortality analysis involved 170,723 study participants without cardiovascular disease or cancer at baseline. During follow-up, there were a total of 23,867 deaths, of which 5492 were due to cardiovascular disease.
Compared with current smokers, deaths due to cardiovascular disease were reduced among those who had stopped smoking regardless of weight change status.
HRs — all significant — were 0.69, 0.47, 0.25, and 0.33 for recent quitters with weight gains of 0, 0.1 to 5.0 kg, 5.1 to 10.0 kg, and more than 10.0 kg.
Among those who had quit smoking more than 6 years previously, the HR for cardiovascular death was 0.50.
For deaths due to any cause, the corresponding HRs for the different categories of weight gain were 0.81, 0.52, 0.46, 0.50, and 0.57, also all statistically significant.
While the cardiovascular mortality advantage tended to wane 10 to 15 years after stopping smoking, the risk for cardiovascular death never reached the level in current smokers, Yu and colleagues report.
Quitters: Don't Be Deterred by Potential Weight Gain
In the statement, Yu noted, "Smokers shouldn't be deterred by potential weight gain after quitting because the short-term and long-term reduction of cardiovascular disease risk is clear."
"However, quitters may want to consider eating a healthful diet and engaging in physical activities to minimize weight gain to keep their diabetes risk at bay and to maximize the health benefits of quitting."
Supported by research grants from the National Institutes of Health. Hu and Schroeder have disclosed no relevant financial relationships.