MONTPELLIER, FRANCE – The first expert consensus on smoking and diabetes, coauthored by the Francophone Diabetes Society (SFD) and the French Society for the Study of Nicotine Addiction (SFT), was presented at the SFD’s annual conference.
Alexia Rouland, MD, an endocrinologist at Dijon Bourgogne University Hospital, Dijon, France, took the conference as an opportunity to list the many benefits of smoking cessation for patients with diabetes, despite the “slight and temporary” risk for blood sugar imbalance.
Societies target smoking
Diabetes societies around Europe have set their sights on the topic of smoking. Indeed, the guidelines published in 2019 by the European Association for the Study of Diabetes and the European Society of Cardiology state that “smoking cessation is obligatory for all prediabetic and diabetic patients” (class I, level A).
This year, the France-based SFD and SFT dedicated an expert consensus to the major problem of smoking in patients with diabetes. The aim was to provide health care professionals with convincing, well-supported arguments in favor of smoking cessation in their patients with type 1 and type 2 diabetes.
“Before anything else, diabetic patients need to be made aware of the risks of smoking,” said Dr. Rouland. “It’s not just about the fear factor, though. It’s also about providing a positive incentive – they need to be told about the ways they’ll benefit from quitting smoking. For example, you have all-cause mortality, macro- and microangiopathic complications, and so on.”
Duration of abstinence
“Diabetic patients who have stopped smoking have a relative risk for all-cause mortality of 1.28 (1.09-1.51), which is less than what you see in active smokers (relative risk = 1.58; 1.42-1.77), but still above that of nonsmokers,” said Dr. Rouland.
A previous study revealed that although the risk does indeed go down after stopping smoking, it is linked to how long ago the person stopped. Patients who stopped smoking less than 10 years ago still had a slightly raised all-cause mortality risk, and this was even higher if they had smoked for 20 years or more.
After 10 years of not smoking, however, the greater all-cause mortality risk was no longer significant in any of the groups monitored (smoking duration, number of cigarettes/day). Concrete evidence of the link between all-cause mortality and the length of time since a person stopped smoking also emerged from the large cohort in the American Nurses’ Health Study.
The relative risk for all-cause mortality in women who stopped smoking less than 5 years ago remained high (RR = 1.96, 1.47-2.67), then decreased over time. After 10 years, it was no longer significant (RR = 1.11, 0.92-1.35).
Macro- and microangiopathic risks
Smoking cessation also has a real benefit in terms of the increased macro- and microangiopathic risks. In type 2 diabetes, a study found an increased relative risk for macro- and microalbuminuria of 1.86 (95% confidence interval, 1.37-2.52) in former smokers, compared with an increased relative risk of 2.61 (95% CI, 1.86-2.64) in current smokers.
In type 1 diabetes, the cumulative risk for microalbuminuria in former smokers was 15.1% vs. 18.9% in smokers and 10% in nonsmokers.
A 2019 meta-analysis of prospective cohort studies determined that smoking is an independent risk factor for diabetic nephropathy, especially in patients with type 1 diabetes.
Yet, most of the data for this condition come from subjects with type 2 diabetes. One publication estimated its prevalence after a 1-year follow-up of the smoking cessation program as 10.9% in former smokers and 15% in those who continued smoking.
In regard to macroangiopathy in the context of type 2 diabetes, the aforementioned 2019 meta-analysis focused on coronary artery disease, cerebrovascular accident (CVA), cardiovascular mortality, and myocardial infarction (MI). It found that smokers face an increased risk for all these outcomes.
The relative risks wavered between 1.53 and 1.66 and decreased after smoking cessation. For coronary artery disease and MI, they became insignificant. There was still a risk for CVA (RR = 1.34; 1.07-1.67) and fatal cardiovascular events (RR = 1.19; 0.02-1.39).
The data are slightly more heterogeneous for type 1 diabetes, where, despite smoking cessation, the increased risk for heart failure and CVA persists in men, yet the same risk for coronary heart disease and CVA drops in women.