Smoking Cessation Has Many Benefits in Diabetes

MONTPELLIER, France — The first expert consensus on smoking and diabetes, co-authored 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 healthcare 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 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 [RR] = 1.58, 1.42 - 1.77), but still above that of nonsmokers," said 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 RR 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% CI, 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.

Risk for Weight Gain

Rouland tried to reassure patients about the risk for gaining weight. "Weight gain is not inevitable. There is a risk for this, but it's temporary. And, even with some weight gain, the cardiovascular benefits are still indisputable."

A study carried out in 2013 focused specifically on this point, with an average post-cessation weight gain of 3.8 kg (8.4 lb) seen in diabetic individuals in the first 4 years after stopping smoking and of 0.1 kg (0.2 lb) thereafter. A time-based effect was observed with regulation of excess weight post-cessation over time, as seen in the general population (3 kg [6.6 lb] on average in nondiabetic individuals).

Weight gain tends to occur mainly in the immediate post-cessation period, essentially in the first 3 months, and there is a large variation in weight change. Some people gain a lot (from 5-10 kg [11-22 lb], or even more than 10 kg), others lose weight (20% of diabetic former smokers in the first month, 7% after 12 months), and 25% gain less than 5 kg (11 lb).

Blood Glucose Imbalance

"A risk for blood glucose imbalance has been reported after smoking cessation, although this is very slight and only temporary," said Rouland.

A British retrospective study examined this question, focusing on glycated hemoglobin in patients with type 2 diabetes. A1c increased by 0.21% (95% CI, 0.17 - 0.25, P < .001) within the first year after quitting. A1c decreased as abstinence continued and became comparable to that of continual smokers after 3 years. This increase in A1c was not mediated by weight change.

Another study published in 2018 on the topic of type 2 diabetes also reported on the risk for poor glycemic control (defined as A1c > 7%) persisting for 10 years after smoking cessation (odds ratio [OR], 1.23; 95% CI, 1.06 - 1.42). Thereafter, between 10 and 19 years post-cessation, the OR decreased to 0.97 (95% CI, 0.80 - 1.19, NS). Beyond 20 years post-cessation, the OR was 1.14 (95% CI, 0.89 - 1.44, NS) and was therefore no longer significant.

Regardless, "the risk for poor glycemic control is lower in quitters than in active smokers," said Rouland.

Quitting and Diabetes Risk

Will a smoker's increased risk for diabetes drop when he or she stops smoking? "This is essentially what happens," Rouland confirmed, "and his or her increased risk for metabolic syndrome also drops. One meta-analysis revealed a time-based effect.

"Patients who had stopped smoking less than 5 years previously had an increased relative risk for type 2 diabetes, and this risk dropped to 1.11 after more than 10 years of not smoking. Moreover, this relative risk for type 2 diabetes remained lower than that of active smokers, at between 1.19 and 1.60, depending on tobacco use."

In regard to the risk for metabolic syndrome, those who quit smoking seem to have an increased risk of 10%, compared with nonsmokers (RR = 1.10, 1.08 - 1.11, P < .001). "But yet again, this increased risk is much lower than that of active smokers, whose risk is between 37% (less than 20 cigarettes/day) and 71% (more than 20 cigarettes/day)."

Women With Diabetes

"The benefits of quitting appear identical, regardless of the sex of the diabetic person," said Rouland. "As in the general population, weight gain after smoking cessation is greater in women. Furthermore, while smoking increases the risk for gestational diabetes (RR: 1.4 - 1.9) and for the use of insulin in this context, stopping smoking reduces these risks.

"Moreover, smoking during pregnancy not only increases the risk for pregnancy-related complications (early miscarriage, ectopic pregnancy, birth defects, placental abruption, premature birth, intrauterine fetal demise, cesarean birth, low birth weight), but it also increases the risk of type 2 diabetes in the newborn. The risk to the newborn is said to be around 34% in cases in which the mother smokes during pregnancy and 22% in cases in which the mother is a passive smoker, thereby justifying the use of measures to help the mother's family members to stop smoking."

Rouland reports no relevant financial relationships.

This article was translated from the Medscape French edition.

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