Background: Studies have shown that smoking increases the risk of acute ST-segment elevation myocardial infarction (STEMI). However, the impact of gender on this risk is unknown.
Methods: This retrospective ecological cohort study examined all patients presenting with acute STEMI undergoing primary percutaneous coronary intervention at the South Yorkshire Cardiothoracic Centre (UK) between 2009-14. Index cases were compared to population data from the UK Office for National Statistics for smoking status, gender and age. Incidence rates of STEMI for current and non-smokers were calculated by gender, and the associated 95% confidence intervals (CI) determined from the Poisson distribution. Age-standardised incidence rate ratios (IRR) comparing STEMI rates between smokers and non-smokers were calculated between genders in three age groups (18-49, 50-64, >65).
Results: There were 2,996 STEMI patients. 27.1% were female, who were significantly older than male patients (mean age: 66.3 vs 60.9, p=0.03). Risk factor prevalence was similar between genders, although hypertension was more common in females (44.9% vs 36.7%, p<0.001). In current smokers, the peak STEMI rate in females was in the 70-79 age range (233⁄100,000 pt/yrs) and the 50-59 (458⁄100,000 pt/yrs) in males. Across all ages, smokers had a significantly higher acute STEMI risk with an IRR of 5.11 (CI: 4.83-5.40). Compared to their non-smoking gender counterparts, females had a significantly higher IRR than males (6.62 (CI: 5.91-7.38) vs 4.46 (CI: 4.18-4.76)), and this difference was significant in all three age groups. The highest IRR was in female smokers in the 18-49 group at 12.67 (CI: 9.69-16.28), vs 8.47 (CI: 7.50-9.53) in males. The most striking difference between genders was in the 50-64 group (IRR 11.03 (CI: 9.33-12.96) vs 4.63 (CI: 4.21-5.08)).
Conclusions: Smoking status had a significantly differential effect between genders, with female smokers at increased risk of acute STEMI over male smokers by a factor of 1.48. Young female smokers (18-49) had the highest IRR and were over 12 times more likely to suffer an acute STEMI than their non-smoking peers. The largest IRR gender difference, by a factor of 2.38, was in the 50-64 age group.