Smoking More Strongly Linked to STEMI in Women Than in Men

Women who smoke are at a greater risk of experiencing STEMI than male smokers, especially those who are under 50 years old, a retrospective cohort study has found. Yet the cardiovascular risks of smoking may reverse as soon as 1 month after people quit the habit.

The study, published in the July 2, 2019, issue of the Journal of the American College of Cardiology, covered more than 5 years of data (January 2009 to July 2014) from the South Yorkshire region of England on patients with acute STEMI managed by primary PCI. According to the researchers, it’s the first to try to isolate the impact of smoking on STEMI rates in this way.

“We know that smoking can cause a heart attack,” senior author Ever D. Grech, MD (Northern General Hospital, Sheffield, England), noted to TCTMD. “But is that risk small? Medium? Large? Is it colossal? . . . What we’ve done for the first time is to identify that risk across all age groups and between genders.”

Identify your smokers, and perhaps be absolutely sure you do an aggressive risk assessment of everything else, particularly in your females. Jacqueline E. Tamis-Holland

Grech, along with lead author James Palmer, MBChB (Sheffield Medical School, England), compared the experience of 3,343 STEMI patients in their region to that of the entire population served by the South Yorkshire Cardiothoracic Centre. The STEMI records included patient age, sex, smoking status, other cardiovascular risk factors, and any cardioprotective drugs taken prior the onset of STEMI. The larger population data set included information on current smokers in the region, as well as people who had smoked in the past.

Women accounted for nearly three in 10 of the STEMI patients (27.3%). The peak STEMI rate was at 70-79 years old for women who currently smoke (235 per 100,000 patient-years) and at 50-59 years old for male smokers (425 per 100,000 patient-years).

The researchers derived an incident rate ratio (IRR) by dividing the STEMI incidence in current smokers by the incidence in ex-smokers or never smokers. While an ex-smoker was defined as someone who stopped smoking at least 28 days prior to experiencing STEMI, the exact timing of this cessation was unknown for 38% of individuals in this group.

Although the absolute number of STEMI cases was higher in men, the impact of smoking on STEMI rates was greater in women (IRR 6.62; 95% CI 5.98-7.31) than in men (IRR 4.40; 95% CI 4.15-4.67). Female smokers ages 18-49 had the greatest increased risk for STEMI of all (IRR 13.22; 95% CI 10.33-16.66). Men in this age bracket also had an elevated risk of STEMI but not to the same degree (IRR 8.60; 95% CI 7.70-9.59).

The incidence rates of STEMI for never smokers and ex-smokers were almost identical, which is why the investigators combined these two groups in the denominator of the IRR. “This suggests marked reversibility in STEMI risk by cessation [of smoking], possibly in as little as a few weeks or months,” Palmer and colleagues note in their paper.

“Our study found that those who did stop smoking were able to reduce their risk of a major heart attack to a level similar to a contemporary who’d never smoked,” Grech elaborated to TCTMD. “That came as a surprise to me. I regard this as a silver lining within the dark cloud of smoking outcomes.”

Those who did stop smoking were able to reduce their risk of a major heart attack to a level similar to a contemporary who’d never smoked. . . . I regard this as a silver lining within the dark cloud of smoking outcomes. Ever D. Grech

One contribution of the study is that it refocuses attention on the fact that female smokers have higher cardiac risk profiles than male smokers. This has been evident since the 1990s; however, “the question of whether this is related to hormonal differences—that smoking somehow interacts with estrogen, and estrogen is protective to the heart—isn’t really clear,” Jacqueline E. Tamis-Holland, MD (Mount Sinai Saint Luke’s Hospital, New York, NY), observed to TCTMD. “It’s interesting that the smoking effects are particularly notable in younger females, which would be at a time when we would expect the estrogen levels to play the most important protective effect.”

For Tamis-Holland, the results also hold ramifications for STEMI prevention. “You can use the opportunity to identify your smokers, and perhaps be absolutely sure you do an aggressive risk assessment of everything else, particularly in [young] females,” Tamis-Holland advises. “You might say, ‘Even though she smokes, she’s only 35 [and] she’s premenopausal, [so] her chance of developing coronary disease is much lower.’ That should not be the attitude.”