About a third of U.S. adults have a collection of risk factors that increases their risk of heart disease and strokes, according to new research.

While previous studies found an increasing prevalence of so-called metabolic syndrome among U.S. adults, researchers report in JAMA that rates remained mostly stable between 2008 and 2012.

The finding should be taken with “cautious optimism,” said coauthor Dr. Robert J. Wong of the Alameda Health System-Highland Hospital Campus in Oakland, California.

But “a huge proportion of the U.S. population is affected, and it puts you at risk for so many diseases,” Wong told Reuters Health. “People should still be very vigilant.”

Metabolic syndrome is present when people have three or more of the following risk factors: abdominal obesity (waist size 40 inches or 102 cm in men or 35 inches or 88 cm in women, or larger), high blood levels of triglycerides, low blood levels of "good" HDL cholesterol, high blood pressure (or use of medication for it), and high blood sugar levels after an overnight fast (or use of diabetes medicines).

According to the American Heart Association, "When a patient presents with these risk factors together, the chances for future cardiovascular problems are greater than any one factor presenting alone."

Using data collected between 2003 and 2012 from the National Health and Nutrition Examination Survey, Wong and his coauthors found that about a third of U.S. adults age 20 and up could be diagnosed with metabolic syndrome.

More than 35 percent of women qualified for the syndrome, compared to 30 percent of men. It was most common among Hispanic people and became increasingly common with age. More than half of women and Hispanics over age 60 had metabolic syndrome.

Overall, the prevalence of the condition increased from about 33 percent of adults in 2003 to about 35 percent in 2012.

Between 2008 and 2012, the overall prevalence of metabolic syndrome in the U.S. was stable, the authors found, and decreased among women.

It’s not clear why the rate went down specifically among women, Wong said.

“Women may be more (likely to) aggressively pursue weight control, which would certainly help,” but this and other explanations are only speculation, Gary Liguori of the University of Tennessee in Chattanooga told Reuters Health by email.

"Awareness on obesity, a big driver of (metabolic syndrome), has increased tremendously in the past 10 years, with many different public health efforts to stem the tide,” said Liguori, who was not involved with the new research.

It makes sense that researchers have seen a plateau in obesity rates followed a few years later by a plateau in metabolic syndrome, he said.

“Having metabolic syndrome is not going to kill you tomorrow but it puts you at risk for health consequences 10 to 15 years from now,” Wong said.

It’s important for health care providers and patients to understand what metabolic syndrome is, he said.

“If you don’t understand what it is, it makes it harder to advocate for your health,” Wong said.

Many of the characteristics of metabolic syndrome are modifiable, so if you have the syndrome, you don’t need to have it forever, Wong said.