Smoking and Acute MI: The Younger the Patient, the Higher the Risk

Compared with people who have quit or never smoked, current smokers face a significantly higher chance of developing acute STEMI, and as striking new data show, the risk conferred by smoking appears to be greatest in the youngest individuals. The numbers highlight the importance of increasing public health messages regarding the cardiovascular risks associated with tobacco use rather than focusing primarily on lung disease, researchers contend.

“Smokers currently have only a vague understanding of the increased risk of an acute MI that smoking confers,” the study’s senior author, Ever D. Grech, MD (Northern General Hospital, Sheffield, England), told TCTMD in an email. “By quantifying the risk and presenting it as a numerical hazard, smokers who may have previously accepted an undefined risk, may find it more difficult to ignore.”

Compared with former and never smokers, current smokers of all ages had triple the risk of acute STEMI (RR 3.26; 95% CI 2.98-3.57). Smokers who were younger than age 50 had the worst discrepancy in risk of all—more than eight times that of former and never smokers (RR 8.47; 95% CI 6.80-10.54). Those who were 50-65 years of age had more than five times the risk of acute STEMI, and those over age 65 years had more than three times the risk compared with similarly aged peers who did not currently smoke.

The data come from a study published online November 29, 2016, in Heart, in which Grech and colleagues led by Amelia Lloyd, MD (University of Sheffield, Sheffield, England), looked at 1,795 STEMI patients undergoing PCI at a single center from January 2009 to April 2012. For comparison, they obtained demographic data from area residents who participated in the Office for National Statistics Integrated Household Survey (ONS-IHS) between April 2009 and March 2012.

The cohort consisted of 48.5% current smokers, 27.2% ex-smokers, and 24.3% never smokers. Current smokers were nearly a decade younger, on average, than ex-smokers and those who never smoked (57.4 years vs 68.5 years and 66.7 years, respectively).

Compared with people who never smoked, former and current smokers were more likely to have a previous history of ischemic heart disease, even after adjustment for age, and current smokers were three times more likely than never smokers to have peripheral vascular disease.

Importantly, rates of STEMI and age at presentation between former and never smokers were comparable, confirming suggestions from other, larger studies that “giving up smoking reduces the incidence of acute STEMI to that of someone who has never smoked, in all age groups,” the researchers write.

To TCTMD, Grech said more research is needed, however, to determine if there is a threshold of years since quitting that determines at what point ex-smokers become risk-equivalent to never smokers, since studies have shown a wide time variation that ranges anywhere from 1 year to more than 10 years.

Furthermore, Grech and colleagues say the reason why smoking imparts such a high risk of acute STEMI among those who are youngest remains unclear, since studies of young smokers have confirmed that they have fewer traditional cardiovascular risk factors than older people. Of note, they hypothesize that smoking may be “perhaps the most powerful of all risk factors, exerting its effect much sooner than any other.”

All the more reason, said Grech, for greater emphasis on public health messages about cardiovascular disease and smoking.

“There is no doubt in my mind that when it comes to the dangers of smoking and heart attacks, the message is not getting through to the public strongly enough,” he observed, adding that there are many more warnings on cigarette packs highlighting the risk for pulmonary and related diseases than for cardiac hazards.

“Although the former are important, we should be reminded that myocardial infarction is the leading cause of death in developed countries,” he noted. “Therefore, an awareness of the risks of smoking is undoubtedly an important public health message, because it potentially allows targeted intervention—especially to younger smokers—with consequent reductions in mortality and morbidity.”