People with naturally thin thighs may be at greater risk for developing heart disease and dying an early death, a Danish study found.

Researchers have been measuring body sizes and shapes for years to look for clues about who is most vulnerable to heart disease, the leading cause of death worldwide. While most of the effort has focused on height, weight and the size of the hips relative to the waist, no one approach stands out, doctors said.

Researchers took detailed measurements and evaluated the body composition of 1,436 men and 1,380 women in Denmark, then tracked their health for more than decade as part of a study conducted on behalf of the World Health Organization. People with the thinnest thighs had a two-fold greater risk of heart disease and death, and the risk rose as thigh size declined.

"The adverse effects of small thighs might be related to too little muscle mass," which can affect fat and sugar metabolism, said researchers led by Berit Heitmann, director of research at Copenhagen University Hospital's Institute of Preventive Medicine. "General practitioners could use thigh circumference as an early marker to identify patients at later risk of cardiovascular disease and early mortality."

The risk remained even after the researchers took into account the volunteers' weight, lifestyle, stomach fat, blood pressure, cholesterol and other factors that influence heart disease. While the risk rose for people with thighs smaller than the average of 60 centimeters (23.6 inches) in circumference, those with larger limbs didn't get additional protection, the study found.

The study, funded by the Danish Medical Research Council, appears in the British Medical Journal. While there are no known methods to specifically reduce stomach fat or waist size, thigh muscle mass increases with physical activity using the lower body, the researchers said.

More study is needed to determine if measuring the thighs with a tape measure will lead to improvements in medical treatment for people at risk for heart disease beyond what has been achieved through existing tests, said Ian Scott, director of internal medicine at Princess Alexandra Hospital in Brisbane, Australia, in an editorial that accompanied the study.

"Randomized trials are needed to test whether interventions that increase thigh muscle mass through increased physical activity, in addition to or separate from current primary prevention strategies, decrease cardiovascular risk more than current practice," Scott wrote. "If this approach is shown to be effective, the public health implications would be intriguing."