The shorter you are, the more your risk of coronary heart disease. That is the take-home message from a new study led by the University of Leicester in the UK and published in the New England Journal of Medicine.
Coronary heart disease is when the arteries supplying blood to the heart become narrowed due to a buildup of plaque.
If a blood clot forms over the plaque then the risk of heart attack is raised, as the artery can become completely blocked.
Coronary heart disease is the most common cause of premature death worldwide.
“For more than 60 years it has been known that there is an inverse relationship between height and risk of coronary heart disease,” explains study leader Prof. Sir Nilesh Samani, British Heart Foundation professor of cardiology at the University of Leicester.
However, it has not been previously clear whether the relationship between height and risk of coronary heart disease has been due to confounding factors in childhood or whether the relationship is more direct.
Examples of potential confounding factors include socioeconomic environment and level of nutrition.
In the new study, Prof. Samani and colleagues present their evidence that shows the association between shorter height and higher risk of coronary heart disease is a primary relationship and is not due to confounding factors.
The researchers looked at genetic data from almost 200,000 people with or without coronary heart disease and examined 180 genetic variants that affect height and coronary heart disease.
Prof. Samani and colleagues found that every 2.5 inch change in height affects coronary heart disease risk by 13.5%. To illustrate this, the researchers provide the example that a 5 ft person has a 32% higher risk of coronary heart disease compared with a 5 ft 6 inch person because of their smaller height.
In the last few years, a large number of genetic variants have been identified that determine height. Prof. Samani explains:
“The beauty about DNA is that it cannot be modified by one’s lifestyle or socioeconomic conditions. Therefore, if shorter height is directly connected with increased risk of coronary heart disease, one would expect that these variants would also be associated with coronary heart disease and this is precisely what we found.”
The team also investigated whether the association between shorter height and coronary heart disease risk could be explained by other known risk factors. The researchers only found an association with cholesterol and fat levels that could explain a third or less of the relationship between shorter height and coronary heart disease.
The authors believe that biological processes that determine height and coronary heart disease development are responsible for the remaining two thirds of the association. One explanation of this could be that people of smaller height have proportionally smaller coronary arteries, so a similar level of plaque to a taller person could result in greater probability of disease.
For Prof. Samani, the findings underscore the complexity of coronary heart disease:
“While our findings do not have any immediate clinical implications, better and fuller understanding of the biological mechanisms that underlie the relationship between shorter height and higher risk of coronary heart disease may open up new ways for its prevention and treatment.”