Highlights:
- Excess body fat and increased body mass index (BMI) cause heart and blood vessel diseases particularly aortic stenosis
- Using Mendelian randomization the team showed that higher BMI and fat mass increase the risk of aortic valve stenosis and several heart diseases, suggesting that excess body fat causes heart disease
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About Mendelian Randomization
- Mendelian randomization analyzes genetic variants already known to be linked to specific risk factors of the disease, such as body fat and BMI, as indirect determinants or proxies for these risk factors.
- This method helps scientists to determine whether a risk factor has a causal relationship to a disease rather than just association, i.e., no cause-effect relationship can be proved.
- Also, using gene variants reduces bias since these are already present at birth and cannot change due to external influences or by the development of other diseases
Relationship Between Excess Fat & Weight to Heart Disease
- The study team analyzed 96 gene variants associated with excess body fat and increased body mass index (BMI) to evaluate their causal effect on 14 heart diseases
- The study included 367,703 participants of white-British origin from UK Biobank - a UK-based national and international data resource about 500,000 people, aged 40-69 years
- Persons with genetic variants predisposing to high BMI had increased risk of aortic valve stenosis, heart failure, high blood pressure, peripheral artery disease, deep vein thrombosis, coronary artery disease, atrial fibrillation and pulmonary embolism
- For each genetically-predicted 1kg/m2 rise in BMI, the increased risk varied from 6% for pulmonary embolism to 13% for aortic valve stenosis
- Presence of gene variants predicting excess body fat resulted in increased risk the highest being for aortic stenosis (46%) followed by ischaemic stroke, TIA (transient ischemic attack), atrial fibrillation, cardiac failure, peripheral artery disease, deep vein thrombosis, hypertension and coronary artery disease
Importance of Diet & Physical Activity in Preventing Heart Disease
Interestingly, the study team emphasizes that although these genetic variants can predispose persons to gain excess weight, the most critical factors that influence the development of heart disease include diet and physical activity.A healthy diet plus physical exercise is the cornerstone to prevent heart disease and we must limit our calorie intake to give sufficient energy to maintain healthy body weight, i.e. a BMI of between 20 to 25 kg/m2. Therefore, people genetically predisposed to high BMI should try harder and strive to maintain optimal body weight.
Professor Larsson said: "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.”
Merits & Demerits of the Study
- The merits of the study include the large numbers of participants and the fact that they were of European descent, thereby reducing the possibility of bias by including different races.
- Possible demerits include the fact that some gene variants may be associated with more than one disease, that the number of cases for some diseases was less, and that there was no data on the severity of aortic stenosis.
Reference:
- Body mass index and body composition in relation to 14 cardiovascular conditions in UK Biobank: a Mendelian randomization study - (https://doi.org/10.1093/eurheartj/ehz388)
Source-Medindia