WEDNESDAY, April 13 (HealthDay News) -- In most people, plaque formation in arteries occurs during a relatively short period of time later in life, according to a new study.

Researchers at the Karolinska Institute in Sweden analyzed plaque samples from people who had surgery to remove plaque buildup in arteries in their neck.

"We suspected that the plaque would be substantially younger than the patients, who were on average 68 years old at surgery, but we were surprised when we found that the average age of these plaques was less than 10 years," study leader Johan Bjorkegren said in a news release from the institute.

He and his team also found that variation in the plaque was low, suggesting that plaque formation in most of the people occurred in a three- to five-year span.

In addition, the age of plaques was associated with the level of insulin in people's blood, and plaques that were formed more recently were more unstable than older plaques and, therefore, more likely to cause clinical complications such as stroke, the researchers said.

"The correlation between low plaque age, higher insulin levels and instability is also consistent with our findings of gene activity where younger plaques were characterized with higher activity of genes related to immune responses and oxidative phosphorylation," Bjorkegren said.

"However, our study is small and needs to be replicated in future, larger clinical studies before we can determine the exact roles of biological age for plaque stability and associated clinical events," he added.

The study was published online April 7 in PLoS One.

More information

The U.S. National Heart, Lung, and Blood Institute has more about atherosclerosis.