Minimize Weight Gain to Maximize Smoking-Cessation Benefit

March 11, 2013

SAN FRANCISCO — A new study of 1000 contemporary smokers shows that those who were able to stop smoking, which was around 40% of the group, gained more weight and had a higher risk of developing impaired fasting glucose (IFG) and type 2 diabetes than those who continued to smoke. The results were reported in a poster at the American College of Cardiology 2013 Scientific Sessions today by Asha Asthana, MD, from the University of Wisconsin School of Medicine and Public Health, Madison.

But "our research does not imply that you're better off keeping on smoking because if you quit you'll get diabetes, senior author James Stein, MD, also from the University of Wisconsin School of Medicine and Public Health, stressed to Medscape Medical News. "To the contrary, we know that people should quit smoking. But there are some patients whose risk of diabetes and [developing] IFG goes up; we are trying to identify the predictors so we can target these people more aggressively for metabolic intervention.

"The findings should not be misconstrued in any way to suggest that any patient is better off if they don't quit smoking," he added. "Even though people gain weight, the benefits of quitting smoking dramatically outweigh any adverse effects of weight gain. We've already shown, in this cohort, for example, that quitting smoking — in spite of weight gain — improves endothelial function and improves lipids."

Study Examined Heavier Contemporary Cohort

Dr. Stein and colleagues explain that contemporary smokers are older "and more overweight than in historical cohorts," so with the long-established knowledge that stopping smoking leads to weight gain, they decided to investigate incident diabetes and IFG 3 years after a quit attempt.

There were 1016 active smokers enrolled in a prospective, randomized clinical trial of 5 smoking-cessation pharmacotherapies. Over half were female (58%), and the majority were white; they were 45.6 years old, on average, had smoked a mean of 21.2 cigarettes/day, and had a smoking history of 29.7 pack-years. Average body mass index (BMI) was 29.1 kg/m2.

After 3 years, 42.9% of the smokers had quit. Abstinent subjects gained more weight (6.5 kg vs 1.7 kg; P < .001) and had a greater increase in fasting plasma glucose (4.5 g/dL vs 0.7 mg/dL; P < .001) than continuing smokers.

IFG prevalence increased from 21.4% to 40.1% in abstinent subjects but only from 20.7% to 22.7% in continuing smokers (P < .001). Diabetes prevalence increased from 3.1% to 11.4% in abstinent subjects but only from 7.2% to 10.5% in continuing smokers (P = .020).

In addition to abstinence at year 3 (p=0.016), baseline independent predictors of incident diabetes were older age (P < .001), BMI (P < .001), and nonwhite race (P = .004), but not cigarettes/day or pack-years. Weight change was strongly associated with year-3 fasting plasma glucose (P < .001).

Goal Is to Mitigate Risk for Diabetes in Smoking Cessation

Dr. Stein stressed, however, that this research is "preliminary" — "it only identifies having a higher [glycated hemoglobin] HbA1c and a higher glucose level as major predictors, but there is a lot more to this story in regard to people's waist circumference, how much weight they gain, and how much they smoke that we still need to tease out.

"What we don't know at this point is how much of this has to do with weight gain per se vs how much has to do with other changes in brain chemistry or other kinds of intrinsic sensitivity to developing diabetes that smokers have. The relationship between smoking, smoking cessation, weight gain, and diabetes is very complicated. It's likely a 2-phase relationship where, early on, when you quit smoking, there's an increased risk of impaired glucose metabolism. However, that goes away with time. Similarly, if you keep smoking, you're at increased risk of diabetes as well," he stressed.

"Our next step is to do mediation analysis to more carefully dissect out which people are most at risk and how we can help prevent them from developing IFG and diabetes.

"The ultimate goal is that a doctor will be able to look at a patient's baseline characteristics — age, sex, how nicotine addicted they are, how much they weigh, what their blood sugar is, etc — and use that to help come up with a risk of developing IFG or diabetes, and then use very aggressive metabolic interventions at the time of smoking cessation to try to mitigate that risk."

Asked what those interventions might be, he said the "obvious ones" are exercise interventions, because exercise improves insulin sensitivity, and nutritional interventions, but others will be explored.

"We hope the medical community and [public] will wait until our final report to pass judgment on this. The most important thing readers should realize is that there's no doubt that quitting smoking is the single best way that people can reduce their risk of cardiovascular disease, lung disease, and several kinds of cancers. It is always best to quit smoking," he concluded.

The authors have disclosed no relevant financial relationships.

American College of Cardiology 2013 Scientific Sessions. Abstract 1185-5. Presented March 11, 2013.