People with type 2 diabetes are at increased cardiovascular risk compared with the general population, and those who smoke further increase their risk, so it is important to encourage smoking cessation. However, weight gain is common when giving up smoking. Weight gain is greatest in the first 6 years after cessation (Hu et al, 2018), and median gains of 4–5 kg compared with people who continue to smoke can occur in the first year and may persist at 10 years. In people with type 2 diabetes, increased calorie intake can worsen glycaemic control.
In previous studies, weight gain in people who stop smoking has been demonstrated to reduce some of the health benefits of cessation, but the studies were small, involved healthy individuals rather than those with diabetes and only assessed smoking status at one point in time. Results have been conflicting.
In the present study, using data from two prospective cohort studies in the US, Liu and colleagues analysed around 10 000 people with type 2 diabetes to estimate the risk of cardiovascular disease (CVD; cardiovascular mortality, non-fatal myocardial infarction or stroke, or coronary bypass or stenting) and mortality following smoking cessation. In the CVD analysis, recent quitters (2–6 years since smoking cessation) who did not gain weight within 6 years had a lower risk of developing CVD compared with people who continued to smoke (HR, 0.77 [95% CI, 0.62–0.95]); however, those who gained 0.1–5 kg or >5 kg had no significant reduction in incident cardiovascular events. For long-term quitters (>6 years since smoking cessation), CVD risk was lower than in current smokers (multivariable-adjusted HR, 0.72 [95% CI, 0.61–0.84]).
In the mortality analysis, conducted in long-term quitters, weight gain in the first 6 years did not alter the benefits of long-term smoking cessation, with quitters significantly reducing their risk of death from any cause compared with current smokers (HR, 0.69 [95% CI, 0.58–0.82]). A similar pattern was seen for cardiovascular and cancer-related mortality.
Limitations of the study were that these were all healthcare professionals and most were Caucasian. There were no details of methods used to assist quitting, such as nicotine replacement therapy and vaping, which themselves may impact health risks.
The authors conclude that long-term smoking cessation in people with type 2 diabetes reduces all-cause, cardiovascular and cancer-related mortality; however, to optimise cardiovascular benefits in the short and long term, we need to help those who quit to avoid weight gain.
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