MedWire News: Tobacco smoking is a major risk factor for the development of ST-segment elevation myocardial infarction (STEMI), with the greatest impact seen in younger patients and women, warn Swedish investigators.

The observed increase in the proportion of milder, non-STEMI cases in recent years may be a result of improved patient management and more sensitive diagnostic tools, argues Lean Björk, from Sahlgrenska Academy University of Gothenburg, and colleagues.

Noting, however, that there have also been changes in risk factors, the team examined data on 93,416 patients aged 25–84 years who were admitted to hospital between 1996 and 2004 with acute MI, extracting information on demographic and clinical characteristics, presentation, investigations, management, and tobacco status.

Overall, 64.4% of the patients were men and 38% presented with STEMI. The proportion of patients with STEMI decreased from approximately 43% in 1996 to 35% in 2004. Over the same period, the proportion of patients who were current smokers at the time of admission increased from 29.2% to 35.0% among STEMI patients and from 21.5% to 23.5% among non-STEMI patients.

Smoking was more common among STEMI than non-STEMI patients, at 31.0% versus 22.9%, and an odds ratio of 1.40. Among men aged <50 years, 58% of STEMI patients were smokers, compared with 47% of non-STEMI patients. In women, the corresponding figures were 67% and 50%.

The team found that smokers aged <65 years were significantly more likely to present with STEMI than non-STEMI, at an odds ratio of 2.01 in women and 1.33 in men. Among patients aged ≥65 years, smoking was still significantly associated with STEMI presentation, but the odds ratios were lower, at 1.33 in women and 1.14 in men.

Interestingly, the results, published in the journal Heart, also show that, among patients aged <65 years, hypertension and diabetes were associated with an increased risk for STEMI, but only in women.

The team concludes: “Overall, tobacco smoking was associated with an increased risk for presenting with ST-elevation, particularly among younger patients and women patients. These results underline the importance of smoking as a major risk factor for presenting with more severe acute MIs.”

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