Physicians' Academy for Cardiovascular Education

Current young smokers more likely to have an acute STEMI compared to young ex-/never-smokers

Lloyd A, Heart, 2016

Pronounced increase in risk of acute ST-segment elevation myocardial infarction in younger smokers

 
Lloyd A, Steel L, Fotheringham J, et al.
Heart 2016; published online ahead of print
 

Background

Large epidemiological studies have demonstrated the association between smoking and acute myocardial infarction (AMI) [1]. According to the National Registry of Myocardial Infarction 2 (NRMI2) registry, smokers present with an AMI on average 14 years earlier compared with non-smokers, and according to the Monitoring of Trends and Determinants in Cardiovascular Disease  (MONICA) trials, the prevalence of smokers is up to 81% in young patients aged 35–39 years with AMI [2,3].
 
However, there are no data comparing the incidence of ST-segment elevation myocardial infarction (STEMI) within young smokers and young non-smokers by using local population data as a denominator.
 
This study provides an incidence analysis and quantification of STEMI risk in the South Yorkshire region of the UK. For this, 2 study populations were used; 1) all South Yorkshire patients over the age of 18 who had undergone percutaneous coronary intervention (PCI) for acute STEMI and 2) South Yorkshire residents over 18 participating in the Office for National Statistics Integrated Household Survey (ONS-IHS) for age-matched comparison, thereby correcting for population smoking trends.
 

Main results

  • There were 1795 STEMI patients and 48.5% were smokers. The mean age of the current smokers with a STEMI was 57.4 years (95% CI: 56.63 - 58.13), approximately 10–11 years less compared with ex- and never smokers (ex-smokers: 68.5 years; 95% CI: 67.48 - 69.61; and never smokers: 66.7 years; 95% CI: 65.50 - 67.84).
  • The overall smoking prevalence was 22.4% and the highest prevalence of current smoking was found in those under the age of 50 (27.3%). The smoking prevalence in individuals under the age of 50 who had suffered an acute STEMI was 74.8%.
  • Current smokers with STEMI requiring PCI, were less likely to have hypertension or DM, but more likely to have a family history of ischaemic heart disease (IHD, P<0.05 for all three). After adjusting for age, the differences in the odds of these risk factors lost statistical significance.
  • Compared with never smokers, ex-smokers and current smokers were more likely to have a previous history of IHD, also after adjustment for age (OR: 2.37; 95% CI: 1.69 - 3.31, P<0.001; and OR 1.45; 95% CI: 1.03 - 2.05, P<0.05, respectively).
  • Current smokers were three times more likely to have peripheral vascular disease (OR: 3.44; 95% CI: 1.56 - 7.59, P<0.005) compared with never smokers.
  • The peak age for incident STEMI in current smokers was in the 60–69 year age group with an incidence rate of over 350 cases per 100 000 patient years at risk. The peak age for incident STEMI in ex- and never smokers was in the 70–79 year age group, with over 100 cases per 100 000 patient years at risk.
  • Current smokers were 3.26 (95% CI: 2.98 - 3.57) times more likely to suffer acute STEMI than ex- and never smokers grouped together. Current smokers under 50 years of age were 8.47 (95% CI: 6.80 - 10.54) times more likely to suffer an acute STEMI compared to their age-matched ex- and never smokers. More specifically, those aged 50-65 years had a rate ratio (RR) of 5.20 (95% CI 4.76-5.69) and those aged over 65 years had an RR of 3.10 (95% CI: 2.67-3.60).
 

Conclusion

Chances for experiencing an acute STEMI are much higher for smokers compared to aged-matched ex- or non-smokers. This difference was substantially higher in the younger; young smokers are over eight times more likely to suffer an acute STEMI compared with aged matched young non-smokers, which was 5 times for those aged 50-65 and 3 times for people above 65 years. The cause underlying these differences remains unclear. Current smokers, in particular the youngest, must be supported to undertake smoking cessation therapy, in order to reduce their risk of acute STEMI.
 
Find this article online at Heart
 

References

1. Dawber TR, Kannel WB, Revotskie N, et al. The epidemiology of coronary heart disease--the Framingham enquiry. Proc R Soc Med 1962;55:265–71.
2. Gourlay SG, Rundle AC, Barron HV, et al. Smoking and mortality following acute myocardial infarction: results from The National Registry of Myocardial Infarction 2 (NRMI 2). Nicotine Tob Res2002;4:101–7.
3. Mähönen MS, McElduff P, Dobson AJ, et al.  Current smoking and the risk of non-fatal myocardial infarction in the WHO MONICA Project populations. Tob Control 2004;13:244–0.