Smokers under 50 years old have 8-fold increased risk of acute STEMI

Cigarette smokers who were younger than 50 years old were more than eight times more likely to have an acute ST-segment elevation MI (STEMI) than non-smokers in their age category, according to an analysis of two studies in the United Kingdom.

Adult smokers between 50 and 65 years old were five times more likely to have an acute MI compared with non-smokers their age, while those 65 or older were three times more likely to have an acute MI compared with non-smokers their age.

Lead researcher Amelia Lloyd, MD, of the University of Sheffield in the U.K., and colleagues published their results online in Heart on Nov. 29.

The researchers analyzed data on adult patients in South Yorkshire who had undergone PCI for acute STEMI at the South Yorkshire Cardiothoracic Center between Jan. 1, 2009, and April 6, 2012. They also evaluated South Yorkshire residents who were at least 18 years old and participated in the Office for National Statistics Integrated Household Survey (ONS-IHS) between April 2009 and March 2012.

The mean age of the 1,795 patients was 63 years old, while 72.9 percent were male. In addition, 48.5 percent of the patients were current smokers, 27.2 percent were ex-smokers and 24.3 percent never smoked. The mean age of current smokers was 57.4 years old compared with 68.5 years old for ex-smokers and 66.7 years old for patients who never smoked.

Based on the ONS-IHS data, the researchers found that the smoking prevalence was 22.4 percent within this population, including 27.3 percent in people younger than 50 years old. Among the people younger than 50 who suffered an acute STEMI, 74.8 percent were smokers.

After adjusting for age, ex-smokers and current smokers were more likely than never smokers to have a previous history of ischemic heart disease. Meanwhile, current smokers were three times more likely than never smokers to have peripheral vascular disease.

The incidence of STEMI in smokers was 59.7 per 100,000 patients years among those younger than 50 years old; 316.9 per 100,000 patients years among those between 50 and 65 years old; and 331.0 per 100,000 patients years among those who were 65 or older.

For patients under 50, smokers had an 8.47-fold increased risk of STEMI compared with non-smokers. Smokers between 50 and 65 had a 5.2-fold increased risk of STEMI, while smokers who were 65 or older had a 3.1-fold increased risk of STEMI.

The researchers cited a few limitations of the study, including its retrospective design. They also excluded patients who died before admission or were deemed unsuitable for PCI.

“From our data alone, it is difficult to explain the much higher risk of acute STEMI imparted by smoking on the youngest patients and raises important questions as to why this should occur,” the researchers wrote. “It is recognized that the youngest populations tend to demonstrate fewer risk factors such as hypertension, hyperlipidemia or diabetes and this has been demonstrated in young STEMI patients who smoke. Therefore, smoking appears to be a much more potent risk of STEMI in the young, as it is one of the very few risk factors present in this group.”