— Ex-smokers prone to gain weight, but less likely to die

by John Gever, Contributing Writer, MedPage Today April 27, 2021

Smokers shouldn’t let the prospect of weight gain deter them from trying to quit the habit, Australian researchers suggested.

In a longitudinal study of nearly 17,000 people, those who quit smoking had weight gains averaging 3.14 kg (6.9 lb; 95% CI 1.39-4.87 kg) more than smokers who continued to smoke, as well as greater increases in body mass index (BMI; mean difference 0.82 points, 95% CI 0.21-1.44), according to Berhe Sahle, PhD, MPH, of the Melbourne School of Population and Global Health in Australia, and colleagues.

Yet despite the apparent adverse metabolic effect, those who quit showed no significant increase in risk for cardiovascular disease or type 2 diabetes, and their risk for all-cause mortality was half that of continuing smokers (HR 0.50, 95% CI 0.30-0.81), the group reported in JAMA Network Open.

And that reduction in risk for early death with smoking cessation didn’t appear to be related to the degree of weight gain. The hazard ratio for all-cause mortality among former smokers was 0.50 (95% CI 0.0.35-1.34) for those who gained more than 10 kg (22 lb), relative to ex-smokers with no weight change; findings were similar for ex-smokers who gained more than two BMI points versus those with no BMI change.

“The benefits of smoking cessation outweighed the risks in terms of reducing mortality in the general population because the risks of the major chronic diseases did not increase regardless of the amount of weight and BMI change after quitting,” Sahle and colleagues wrote.

That study participants — who also included never-smokers as well as current and former cigarette users — gained weight after quitting was no surprise, as it had been documented in many previous studies. What’s new, the researchers said, was the finding that mortality as well as risk of chronic metabolic conditions didn’t seem to be affected.

In that respect, the Australian study appears to contradict results from a major U.S. study. In 2018, researchers analyzing longitudinal data from the long-running Nurses’ Health Study I and II and the Health Professionals Follow-up Study found increased rates of type 2 diabetes among ex-smokers compared with continuing smokers, which were proportional to the amount of weight gain.

But that analysis, too, showed that overall and cardiovascular mortality was still reduced among former smokers despite the higher risk for diabetes.

The Australian study included 16,663 adults recruited from 2006 to 2014 as part of a national survey chosen to be representative of the general population. They included 7,842 people who never smoked, 3,588 current smokers, and 5,233 former smokers. Among the latter, about half had quit more than 6 years earlier, and most of the rest more than 2 years previously.

Mean participant age was about 43. During mean follow-up of 6.0 years (SD 3.7), most gained weight, averaging 2.0 kg among never-smokers, 1.7 kg for current smokers, and 1.5 kg for those who had quit.

Besides metabolic conditions, Sahle and colleagues also looked for differences in risks of cancer and chronic obstructive pulmonary disease (COPD). For the most part, there were none, except that COPD was markedly less common in never-smokers than in either current or former smokers. As in the other analyses, the degree of weight gain did not correlate with risks for these conditions.

Limitations to the study, the researchers said, included that many outcomes, including weight, BMI, and medical conditions, were self-reported and thus subject to recall bias and underreporting, and that smoking status also was not independently confirmed.