Risk of Death Increased by 50% in Smokers With Diabetes

Veronica Hackethal, MD

September 02, 2015

Being a smoker and having diabetes increases the relative risk of total mortality and cardiovascular events by about 50%, and quitting smoking can reduce these risks, according to a new study published online August 26 in Circulation.

"Smoking should be routinely evaluated and closely monitored for diabetic patients. As shown in our study, active smoking is associated with increased risks of total mortality and various cardiovascular events among diabetic patients," commented first author An Pan, PhD, of Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.

"Therefore, smoking cessation still remains a major target for patients who smoke," Dr Pan added.

"We also found that former smokers had substantially reduced risks compared with current smokers, although not totally returned to the risk of never smokers, suggesting that quitting smoking is beneficial in the long run for diabetic patients," he emphasized.

According to background information in the article, as many as one-fifth of patients with diabetes are smokers. Studies have pointed to smoking as one of the leading risk factors for diabetes, cardiovascular disease (CVD), and total mortality in the general population. And diabetes also increases the risk of cardiovascular disease and other complications like retinopathy, nephropathy, and neuropathy.

"Despite the global efforts to combat tobacco use and clinical recommendations of smoking cessation for diabetic patients, many patients continue to smoke after diagnosis," Dr Pan stated.

New Data Most Comprehensive Yet, Should Motivate People to Quit

The new review is more comprehensive than past ones — for example, it includes nearly double the amount of studies and almost 10 times more participants than a former meta-analysis in 2011.

Although many studies have looked at the links between smoking and subsequent risks of mortality and morbidity, the results vary across trials, according to Dr Pan.

A comprehensive review and meta-analysis that puts a firm number on the risk of smoking-related health hazards in diabetic patients can inform clinical guidelines for diabetes management and motivate patients to change their smoking behaviors, he explained.

The analysis included prospective cohort studies that evaluated the association between active smoking and risk of total mortality and cardiovascular events in patients with type 1 or type 2 diabetes.

The researchers conducted a search of MEDLINE and EMBASE for English-language articles published to May 2015. They also did a manual search of reference lists in relevant publications. All studies used self-reported smoking status.

The results showed a 55% increased risk of total mortality in diabetic patients who smoked (pooled adjusted RR of 1.55 in 48 studies with 1,132,700 participants and 109,966 deaths) and a 49% increased risk of cardiovascular mortality (RR, 1.49; 13 studies with 37,550 participants and 3163 deaths).

Diabetic smokers also had a 44% increased risk for total cardiovascular disease (pooled RR, 1.44; 16 studies), a 51% increased risk for coronary heart disease (21 studies), a 54% increased risk for stroke (15 studies), a 43% increased risk for heart failure (four studies), and a more than twofold increased risk for peripheral artery disease (RR, 2.15; three studies).

Methodology and study populations varied largely between studies, which could have limited the meta-analysis. Possible publication bias for total mortality and CVD and the inclusion of English-language-only publications could also have limited the study. In addition, the findings may not be generalizable to Asians and type 1 diabetics, who were underrepresented in studies, the authors note.

More Work Needed to Evaluate Smoking-Cessation Effects

Additional analyses suggested that active smoking accounted for 14.6% of total deaths in men and 3.3% in women (about 438,000 deaths annually) in diabetic patients worldwide.

Quitting smoking decreased these risks. Compared with people who never smoked, former smokers had a 19% increased risk for total mortality, 15% increased risk for cardiovascular mortality, 9% increased risk for CVD, and 14% increased risk for coronary heart disease. Former smokers had about the same risk for stroke as never smokers (RR, 1.04).

More studies are needed to evaluate the efficacy and effectiveness of smoking-cessation interventions, Dr Pan pointed out.

Smoking-cessation success rates are notoriously low and may dip as low as 20%, he and his colleagues state.

"Some smokers with diabetes might be concerned about the short-term weight gain and deterioration in glycemic control after quitting smoking, but the current evidence clearly supports a long-term net cardiovascular benefit of smoking cessation among diabetic patients," he concluded.

The authors report no relevant financial relationships.

Circulation. Published online August 26, 2015. Abstract

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