Compared to a decade ago, fewer Americans have a cluster of risk factors that together can signal heart troubles and diabetes down the line, according to a new study.
But while so-called metabolic syndrome is declining, some of its components - including large waistlines and poor blood sugar control, which carry their own risks - are becoming more common, researchers found.
"I don't think we're out of the woods yet," said Gary Liguori, who has studied metabolic syndrome at the University of Tennessee at Chattanooga but wasn't involved in the new research.
"It may be the incidence of diabetes is going to continue to go up," he told Reuters Health.
Researchers led by Hiram Beltran-Sanchez from Harvard University in Cambridge, Massachusetts, used national health and nutrition surveys to track rates of the five traditional components of metabolic syndrome: high blood pressure, high triglycerides, low HDL ("good") cholesterol, high blood sugar and waist circumference greater than 40 inches for men or 35 inches for women.
People who met at least three of those five criteria were considered to have metabolic syndrome, which has been linked to heightened risk of heart disease, stroke, kidney disease and type 2 diabetes.
Overall, the study population's rate of metabolic syndrome dropped from 25.5 percent during the 1999-2000 surveys to 22.9 percent during 2009-2010, Beltran-Sanchez and his colleagues found.
In particular, rates of high blood pressure, high triglycerides and low HDL cholesterol all fell as more people took hypertension and cholesterol drugs.
Because of that, researchers might expect Americans to have fewer cardiovascular problems in the future, according to Beltran-Sanchez.
However, the proportion of study participants with high blood sugar rose from 12.9 percent to 19.9 percent, and the rate of abdominal obesity, or a large waist circumference, increased from 45.4 percent to 56.1 percent.
Liguori said the findings suggest doctors are getting better at reaching out to people who need medication, and more patients are taking their medicines as prescribed.
"When we looked at blood pressure or cholesterol levels that have declined, these declines align very well with the increased use of medication," Beltran-Sanchez told Reuters Health.
"But when we looked at waist circumference, there is really no treatment in some ways, really no medication."
Liguori said rates of abdominal obesity among women, in particular, were concerning.
During the study period, the proportion of women with large waistlines increased from 53.5 percent to 65.4 percent, according to the results published in the Journal of the American College of Cardiology.
"I just hope people don't think, ‘Well it's just a little weight gain, it's not a big deal,'" Liguori said. "Because it does tend to lead to insulin resistance, which then leads to diabetes."
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