Smokers could be doubling their risk for a type of aneurysm that is usually fatal if it ruptures, researchers say.

An abdominal aortic aneurysm (AAA) occurs when the aorta, the main vessel supplying blood to the lower body, becomes enlarged or bulges due to weakening of its walls. The problem can be treated if it’s detected - but if a tear or rupture happens, only about one in five people will survive, according to the National Library of Medicine.

“We already knew that smoking is a very strong risk factor for AAA,” said lead author Dr. Weihong Tang of the University of Minnesota in Minneapolis. “This study adds to the literature by reporting AAA lifetime risk from a community-based cohort with long follow-up,” Tang told Reuters Health by email.

The researchers used data from more than 15,000 middle-aged people who were at risk of developing AAA based on an initial assessment between 1987 and 1989. The participants made three subsequent visits for exams and assessments through 1998.

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Nearly 6,000 people were still alive between 2011 and 2013 and underwent an ultrasound exam at a fifth assessment visit then.

Over the 22-year follow-up period, there were 590 diagnosed, ruptured or repaired AAAs. In 2011, the ultrasound scans found 75 more cases that had gone undetected.

Based on these results, researchers calculated that for participants who began the study, 1 in 17 would go on to develop an AAA, including 1 out of every 9 current smokers and 1 out of 12 former smokers.

People who had quit smoking within eight years of the final assessment in 2001-2003 had higher risk of aneurysm than those who had quit earlier, according to the results in Arteriosclerosis, Thrombosis and Vascular Biology.

“An AAA is a slow and gradually expanding process, and most commonly goes without any symptoms,” said Dr. Otto Stackelberg of the Karolinska Institute in Solna, Sweden, who was not part of the new study.

“These results should not be interpreted as if it is OK to start smoking since the risk of AAA eventually decreases anyway if you quit,” Stackelberg told Reuters Health by email. “Nonetheless, results in the current study are encouraging in the sense that it is never too late to quit, given that those who ceased to smoke had, on average, 29 percent lower risk of developing AAA during their lifetime as compared with those who continued to smoke.”

There was a steep increase in risk for female smokers, as for male smokers, but the U.S. Preventive Services Task Force only recommends ultrasound screening for current or former male smokers between the ages of 65 and 75, the authors note.

“AAA affects about 5 to 9 percent of Americans who are 65 years or older,” Tang said. “Smoking may act through activation of chronic inflammation, which in turn activates enzymes that degrade elastin and collagen fibers of the aortic wall.”