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Weight gain after smoking cessation increases risk for type 2 diabetes

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August 15, 2018

Qi Sun
Qi Sun

Men and women who gain weight in the 5 to 7 years after quitting smoking experience a short-term, increased risk for type 2 diabetes vs. current smokers and those who do not gain weight after smoking cessation, according to findings published in The New England Journal of Medicine.

Weight gain after quitting smoking may lead to a temporarily increased risk of developing type 2 diabetes, although the long-term substantial reduction in cardiovascular or total mortality is sustained regardless of weight gain after quitting,” Qi Sun, MD, PhD, associate professor in the department of nutrition at Harvard T.H. Chan School of Public Health, told Endocrine Today. “Quitters who manage to avoid substantial body weight do not have a significant risk of developing diabetes and thus can benefit the most from smoking cessation.”

Sun and colleagues analyzed data from adults without diabetes, cardiovascular disease or cancer at baseline participating in the Nurses’ Health Study (study baseline, 1984), the Nurses’ Health Study II (study baseline, 1991) and the Health Professionals Follow-up Study (study baseline, 1988), who completed health- and lifestyle-related questionnaires every 2 years by mail. For each 2-year survey cycle, researchers identified participants who reported being smokers in a past cycle but were past smokers in a current cycle, assuming the beginning of the previous cycle as the onset of quitting. Researchers calculated duration of smoking cessation from the onset of quitting to the relapse of smoking, occurrence of study outcomes (diabetes or death) or end of follow-up. Quitters were defined as transient quitters (past smokers in the current cycle but current smokers in previous or next cycles), recent quitters (2 to 6 consecutive years since smoking cessation) and long-term quitters (at least 6 consecutive years since smoking cessation).

Researchers focused on weight change within the first 6 years after smoking cessation, with cutoff points of 0.1 kg to 5 kg, 5.1 kg to 10 kg and more than 10 kg, in addition to a “no weight gain” group. Physical activity and diet were also analyzed. Researchers used Cox proportional hazards regression models to examine the association between smoking cessation and incidence of type 2 diabetes, CVD death and death from any cause.

Diabetes risk

During a mean follow-up of 19.6 years, researchers confirmed 12,384 cases of type 2 diabetes.

The researchers found that, overall, recent quitters had a higher risk for type 2 diabetes vs. current smokers, with the risk for type 2 diabetes peaking at 5 to 7 years after quitting and gradually decreasing thereafter. When the analysis was restricted to only Nurses’ Health Study participants with the longest follow-up duration (since 1978), risk for type 2 diabetes dropped to a level compared with those who never smoked after 30 years’ cessation, according to researchers.

 

Among quitters, weight gain after smoking cessation influenced the level of short-term type 2 diabetes risk. Compared with current smokers, the HR for type 2 diabetes among quitters with no weight gain was 1.08 (95% CI, 0.93-1.26); however, the HR rose to 1.59 for quitters who gained more than 10 kg after smoking cessation (95% CI, 1.36-1.85).

“The risk of type 2 diabetes among recent quitters without weight gain more quickly approached the risk among persons who had never smoked than did the risk among quitters who gained weight,” the researchers wrote, adding that the “peak of risk” was observed among quitters with the most weight gain at 5 to 7 years after smoking cessation.

All-cause, CV death

During follow-up, 23,867 participants died, including 5,492 from CVD. The researchers observed a substantial reduction in both CVD and all-cause mortality after smoking cessation when compared with current smokers.

Compared with current smokers, HRs for CVD death for recent quitters ranged from 0.69 (95% CI, 0.54-0.88) for those without weight gain after smoking cessation to 0.33 (95% CI, 0.18-0.6) among quitters with weight gain of more than 10 kg, according to researchers. Corresponding HRs for death from any cause ranged from 0.81 (95% CI, 0.73-0.9) for recent quitters with no weight gain to 0.57 (95% CI, 0.54-0.59) for recent quitters with weight gain of at least 10 kg, when compared with current smokers.

“Cubic spline analyses showed that cardiovascular mortality decreased substantially after quitting, reached a nadir at 10 to 15 years, and then rose slowly but never reached the level of current smokers,” the researchers wrote.

The researchers noted that, in a small group of smokers with weight gain of at least 18 kg at 6 years after smoking cessation (0.13% of total person-years), CV mortality gradually approached the level of current smokers during an extended follow-up.

“Quitters should monitor their weight change after quitting to maximize their health benefits of quitting smoking,” Sun said. “Improving diet quality and engaging in physical activities may aid quitters to maintain an optimal body weight. In addition, weight gain should not become an obstacle for smokers to consider quitting and will not negate the health benefits of substantial reduction in the risk of premature deaths due to cardiovascular disease or other conditions.”

Benefits outweigh risks

In an editorial accompanying the study, Steven A. Schroeder, MD, distinguished professor of health and health care in the department of medicine at the University of California, San Francisco, noted that most smokers gain weight when they stop smoking — typically less than 10 lb, but as much as 30 lb — as a result of increased appetite and lower energy expenditure. The risk for incident type 2 diabetes associated with such weight gain, Schroeder wrote, gradually abates over time, and was directly proportional to the amount of weight gained.

“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,” Schroeder wrote. “It should be acknowledged, however, that the participants in all 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.” – by Regina Schaffer

Disclosures: The authors and Schroeder report no relevant financial disclosures.

 

 

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