Short people may be more likely to have heart disease, and that increased risk could be linked to the genetics that also determine height, a British-led research team suggests.
A person's risk of heart disease increases about 13.5 percent for every 2.
5 inches of difference in height, the scientists said. That means a 5-foot-tall person has an average 32 percent higher risk of heart disease than a person who's 5-foot 6-inches tall, according to the researchers.
An in-depth genetic analysis of more than 18,000 people revealed a number of genes linked to human growth and development that likely play a role in the increased risk for heart disease.
"We found that people who carry those genetic variants that lower your height and make you shorter are more likely to develop coronary heart disease," said Dr. Nilesh Samani, a professor of cardiology and head of the department of cardiovascular sciences at the University of Leicester in England.
However, while the current study was able to show an association between genetics, height and a higher risk of heart disease, it wasn't able to prove a cause-and-effect relationship.
The study is published online April 8 in the The New England Journal of Medicine.
Heart disease occurs when the arteries that supply blood to the muscles of the heart become narrowed, as a result of fatty plaques that build up along the artery walls. If a blood clot forms within a plaque-narrowed section of artery, it can block blood flow to the heart muscle and cause a heart attack.
But researchers found that only a third of the increased genetic risk they observed comes from genes related to levels of "bad" LDL cholesterol and triglycerides in the body.
That means most of the heart disease risk related to shortness of stature is tied to other genetic factors that are as yet poorly understood, said Dr. Ronald Krauss, director of atherosclerosis research at Children's Hospital Oakland Research Institute in California.
"The genetic data is sufficiently strong to argue there's something else going on," Krauss said. "What that might be is still conjectural."
Some genes identified by researchers could influence heart disease risk by affecting the growth of cells in the artery walls and the heart, Krauss and Samani said.
"These variants could affect the arterial walls in a way that makes them more likely to develop atherosclerosis," the medical term for narrowed or hardened arteries, Samani said.
Other genes appear to be linked to inflammation in the body, which is another risk factor for heart disease, Krauss said.
It's been known for more than 60 years that people who are shorter run a higher risk of heart disease, but this is the first study to suggest that genetics are a primary cause, Samani said.
Up to now, doctors have been unable to rule out other possible explanations, he said. For example, one theory has held that people grow up shorter due to poor nutrition, which also predisposes them to heart disease.
To better understand the heart risks associated with short stature, researchers pooled data from two recent international research efforts into the human genome, one of which explored the genetics of height and the other the genetics of heart disease, said study co-author Dr. Christopher O'Donnell, associate director of the Framingham Heart Study for the U.S. National Heart, Lung, and Blood Institute.
The research team first tested the association between a change in height and risk of coronary artery disease by examining 180 different height-associated genetic variants in nearly 200,000 people, and concluded there's a relative 13.5 percent increase in heart disease risk for every 2.5 inches shaved off a person's height.
They then drilled down to very specific individual genetic data from a smaller pool of more than 18,000 people. They identified a number of pathways by which genes related to height could also influence heart disease risk.
Interestingly, the effect of height on heart disease risk may be gender-specific. "We found a clear-cut effect in men, but we didn't see a clear-cut effect in women," Samani said, adding that significantly fewer women in the study could have affected the statistics.
Samani, Krauss and O'Donnell all said that these results are preliminary, and don't indicate that short people need to do anything other than what's already recommended for everyone to lower heart disease risk, such as eat a healthy diet and get regular exercise.
"We have an abundance of evidence that every person should look at their modifiable risk factors and speak with their doctors," O'Donnell said. "It's not clear what one can do about their height, but it's very clear there are a lot of behaviors one can change to improve their health overall."