Researchers use genetics to determine cause of cardiovascular disease
Excess weight and body fat cause a range of heart and blood vessel diseases, according to a new study published in the European Heart Journal.
Using data from the U.K. Biobank, researchers studied 96 genetic variants associated with body mass index (BMI) and body fat mass to estimate their effect on 14 cardiovascular diseases in 367,703 participants of white-British descent.
Researchers found people who had genetic variants that predict higher BMI were at increased risk of aortic valve stenosis, heart failure, deep vein thrombosis, high blood pressure, peripheral artery disease, coronary artery disease, atrial fibrillation, and pulmonary embolism. For every genetically predicted 1kg/m2 increase in BMI, the increased risk ranged from 6 percent for pulmonary embolism to 13 percent for aortic valve stenosis, according to the study abstract.
The researchers also found that risk of cardiovascular diseases increased with the genetic variants predicting increases in fat mass. The greatest increased risk was also for aortic valve stenosis with a 46 percent increased risk, followed by ischemic stroke, transient ischemic attack, atrial fibrillation, heart failure, peripheral artery disease, deep vein thrombosis, high blood pressure, and coronary artery disease.
This is the first study to use a method called Mendelian randomization, a way of showing whether individual risk factors cause disease, rather than just being associated with it. It uses genetic variants that are already known to be associated with potential risk factors, such as BMI and body fat, as indirect indicators or "proxies" for these risk factors. This enables researchers to discover whether the risk factor is the cause of the disease, rather than the other way around, and reduces bias in results because genetic variants are determined at conception and cannot be affected by subsequent external or environmental factors, or by the development of disease.
The strengths of the study include the large numbers of people involved and the fact that they were of European descent, which reduces the potential for bias from different populations. Potential limitations are that some genetic variants may be associated with more than one characteristic, that the number of cases were few for some diseases, and that there was a lack of information on the severity of aortic valve stenosis, researchers said.
The researchers stress that although these genetic variants can predispose people to be more likely to gain excess weight, the most important factors implicated in the development of cardiovascular disease are diet and physical activity, according to Susanna Larsson, PhD, associate professor and senior researcher at the Karolinska Institute in Stockholm, Sweden.
"Our genes can make us somewhat more predisposed to gain body weight but lifestyle factors, such as overeating and lack of physical activity, are the major determinants of overweight,” said Larsson in a statement. “A healthy diet is the cornerstone of cardiovascular disease prevention, and how much we eat should be limited to the amount of energy required to maintain a healthy body weight, which is a BMI of between 20 to 25. People who are predisposed to a higher BMI may need to work a bit harder to maintain a healthy weight."