Among patients with type 2 diabetes (T2D) who smoke, smoking cessation without subsequent weight gain is associated with reduced cardiovascular morbidity and all-cause mortality. Weight gain after smoking cessation only partially attenuates this beneficial effect on cardiovascular morbidity, according to study results published in The Lancet Diabetes & Endocrinology.
Although smoking cessation has important beneficial effects for patients with T2D, the long-term effects of weight change after smoking cessation are unclear. The goal of the current study was to investigate the association between smoking cessation and subsequent weight change with cardiovascular morbidity and mortality among adults with T2D.
The researchers analyzed data from 2 prospective cohorts in the United States: the Nurses’ Health Study (1976-2014) and the Health Professionals Follow-Up Study (1986-2014). They identified individuals with preexisting T2D or those who developed T2D during the study period without cardiovascular disease (CVD) or cancer at T2D diagnosis.
The primary analyses were incidence of CVD and mortality associated with weight change during the first 6 years of smoking cessation. Assessment of CVD was stratified between the risk during the 2 to 6 years after smoking cessation (recent quitters) and >6 years since cessation (long-term quitters). For mortality analyses, the researchers focused on mortality in the long-term quitting window.
The analysis of CVD included a total of 10,809 patients with T2D, and the mortality analysis included 9688 patients.
In the CVD analysis, there were 2580 incident cases during 153,166 person-years of follow-up. Of 10,809 patients, 24.4% were current smokers at T2D diagnosis. Among recent quitters who did not gain weight within 2 to 6 years since smoking cessation, the risk for CVD was significantly lower compared with those who continued to smoke (adjusted hazard ratio [aHR], 0.77; 95% CI, 0.62-0.95), whereas in those who gained weight after cessation, there was no significant difference in risk for CVD.
In the mortality analysis, there were 3827 documented deaths during 152,811 person-years of follow-up of long-term quitters who survived >6 years after smoking cessation. The researchers found that weight gain within 6 years after smoking cessation did not attenuate the inverse association between mortality and long-term quitting.
For quitters without weight gain after smoking cessation, all-cause mortality risk was significantly lower compared with those who continued to smoke (aHR, 0.69; 95% CI, 0.58-0.82), and this protective effect of smoking cessation was also evident in those with a weight gain of 0.1 to 5.0 kg (aHR, 0.57; 95% CI, 0.45-0.71) or >5.0 kg (aHR, 0.51; 95% CI, 0.42-0.62). Similar patterns of associations were apparent for CVD and cancer mortality; the researchers stated that “long-term quitters had substantially lower all-cause and cancer mortality and incidence of cardiovascular disease, irrespective of weight gain within the first 6 years after quitting.”
The researchers acknowledged several limitations to the study, including that they restricted the analyses to a population of health professionals; used self-reported data for weight and smoking, which were subject to social-desirability bias; and lacked direct measurement of diabetes control and severity.
“These data provide evidence that not only supports the overall health benefits of quitting smoking in the prevention of morbidity and mortality among individuals with type 2 diabetes, but also emphasizes the importance of weight management after smoking cessation to maximize its health benefits,” concluded the researchers.
Liu G, Hu Y, Zong G, et al. Smoking cessation and weight change in relation to cardiovascular disease incidence and mortality in people with type 2 diabetes: a population-based cohort study. Lancet Diabetes Endocrinol. 2020;8(2):P125-133.