At 45 years old, 10.9 percent of men and 2.8 percent of women are at risk of sudden cardiac death before they turn 85, according to a study of participants free from cardiovascular disease at baseline.

Lead researcher Brittany M. Bogle, PhD, MPH, of the Feinberg School of Medicine at Northwestern University in Evanston, Illinois, and colleagues published their results online in the Journal of the American Heart Association on June 29.

The researchers defined sudden cardiac death as “a death attributed to [coronary heart disease] within 1 hour of symptom onset with no other probable cause of death suggested from the medical record.”

Each year, approximately 180,000 to 450,000 people in the U.S. die from sudden cardiac death, which the researchers noted often occurs in people with no overt symptoms of cardiovascular disease. Although lifetime risk estimates for several types of cardiovascular disease have been reported, no study has examined the cumulative lifetime risk for sudden cardiac death, according to the researchers.

For this analysis, they evaluated patients who enrolled in the Framingham Heart Study, a community-based prospective epidemiological study of men and women between 28 and 62 years old in Framingham, Massachusetts. Participants in this study were free from cardiovascular disease at their first examination and were followed up with laboratory tests every two years.

The researchers used data from the Framingham Heart Study to estimate the cumulative lifetime risk for sudden cardiac death at age 45, 55, 65 and 75 years old.

During the follow-up period, 375 people experienced sudden cardiac death.

At age 45, the lifetime risk for sudden cardiac death was 10.9 percent in men and 2.8 percent in women. The risk was 11.2 percent in men and 3.4 percent in women at age 55; 10.1 percent in men and 3.4 percent in women at age 65; and 6.7 percent in men and 2.4 percent in women at age 75.

“The majority of [sudden cardiac death] events occurred before age 70 years, indicating a substantial burden of sudden and premature mortality that is potentially preventable,” the researchers wrote.

They added that high blood pressure was the best risk factor at predicting the lifetime risk of sudden cardiac death in men and women. They also noted a recent study that found sudden cardiac death could lead to two million years of potential life lost in men and 1.3 million years of potential life lost in women, which they said was greater than for any individual cancer and most other leading causes of death.

Limitations of the study, according to the researchers, include that all participants were white, so the results may not be generalizable to other races or ethnic groups. The study also had a limited follow-up period and large confidence intervals for some estimates, which may have led to unreliable conclusions. Still, they believe that the findings may help identify patients at risk for sudden cardiac death.

“Currently, effective methods for early prediction of [sudden cardiac death] do not exist,” the researchers wrote. “Our results suggest that using the easily ascertained risk factors of age, sex, [systolic blood pressure/diastolic blood pressure] and total cholesterol levels, current smoking status and diabetes mellitus diagnosis to categorize people into risk burden groups may be useful in stratifying lifetime risk for [sudden cardiac death].”