Look up or look down?
It seems the shorter you are, the greater your risk from becoming a victim of coronary heart diseases such as myocardial infarction or sudden coronary death.
A new study led by the University of Leicester in the UK and published in the New England Journal of Medicine said this relationship might be because short people have proportionally smaller coronary arteries, or the vessels that deliver oxygen-rich blood to the myocardium (the heart muscle).
The first sign of coronary heart disease is usually a heart attack. In coronary heart disease, the coronary arteries become narrowed or completely blocked due to a buildup of plaque. 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," said study leader Prof. Sir Nilesh Samani, British Heart Foundation professor of cardiology at the University of Leicester.
In the new study, Prof. Samani and colleagues present evidence showing the association between shorter height and higher risk of coronary heart disease is a primary relationship and is not due to confounding factors such as socioeconomic environment and level of nutrition.
They looked at genetic data from some 200,000 people with or without coronary heart disease. They also examined 180 genetic variants that affect height and coronary heart disease.
What they discovered was that every 2.5 inch change in height affects coronary heart disease risk by 13.5 percent. In other words, a 5 foot tall person has a 32 percent higher risk of coronary heart disease compared with a 5 ft. 6 inch person because of their smaller height.
"In the context of major risk factors this is small -- smoking increases the risk by 200-300% -- but it is not trivial", said Prof. Samani.
"I wouldn't say shorter people need to take greater precautions, because if you're 6 ft. 1 in. (1.85 m) you still need to stop smoking. This is only one of many factors affecting risk, everybody should be cautious."
Researchers believe some of the genes affecting a person's height might also be controlling both growth and blood vessel development. In the last few years, a large number of genetic variants have been identified that determine height.
"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", said Prof. Samani.
The team also found no significant association between shorter height and coronary heart disease risk that could be explained by other known risk factors. They 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.
They believe biological processes that determine height and coronary heart disease development are responsible for the remaining two thirds of the association.
"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" said Prof. Samani.
On the flip side, however, are other studies that show height increases the risk of cancer.
One of these studies by the University of Oxford showed being tall is linked to a greater risk of 10 common cancers. For every four inches (10 cm) above five feet, a person has a 16 percent increased cancer risk.
The study involving over one million women suggested chemicals that control growth might also affect tumors. It was published in The Lancet Oncology.
