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12.12.2021 | ח טבת התשפב

High BMI and Lower Risk for Mortality Following Heart Attack?

Research findings show a lower mortality risk following Acute Myocardial Infarction in patients who are overweight as compared to those who have low or normal Body Mass Index, or are obese


According to conventional wisdom, there is a link between obesity and the risk of developing and surviving myocardial infarction (a heart attack). But a study conducted at Bar-Ilan University shows a more complex relationship, expressed in a J-shaped curve – which indicates actually that patients who were admitted with an acute heart attack and had “moderate obesity” as expressed in their body mass index (BMI) survived significantly better even compared to patients with lower or normal BMI. These findings are consistent with previous studies that exhibit what is known as the “obesity paradox.”

The study, conducted by a group of researchers from Bar-Ilan University’s Azrieli Faculty of Medicine, the Hebrew University, Harvard Medical School, the University of Toronto, and Louisiana State University, examined the association between BMI and risk of death from myocardial infarction as is evident in hospitals and mortality rates in contemporary times.

The study included data from 125,405 men and women hospitalized in the United States following myocardial infarction in the years 2015-2016. These patients were divided into six BMI groups, from underweight to extreme obesity. In addition to the BMI, demographics and data pertaining to hospitalization duration and total mortality were collected. Statistical analysis was used to identify predictors of hospital mortality and duration of hospitalization.

The findings show that people in the underweight, normal weight, and extremely obese groups, were at higher risk of mortality during hospitalization after the infarction. In fact, patients with moderate to high overweight BMI were less likely to die following a heart attack. The data is expressed as a J-shaped curve between BMI and the risk of death following myocardial infarction. In other words, the risk of mortality was lower among patients with moderate-high overweight whose BMI was over 25, compared to normal- and low-weight patients, and those who were extremely obese.

According to the researchers, the “obesity paradox” seems to persist even regarding surviving a heart attack.  That is, contrary to popular belief, being “moderately” overweight may provide a “protective effect” against mortality from various diseases. Prof. Offer Amir, of Bar-Ilan University’s Azrieli Faculty of Medicine and the Hebrew University, who is a member of the research team, explains the paradox: “Most likely in the ‘normal-low BMI’ group, there was actually an increased risk of mortality during hospitalization following a cardiac event. A low BMI may be associated with increased mortality and morbidity, due to being linked with, among other things, less muscle mass (which is expressed in low BMI) as well as “calorie reserve” needed for coping with a serious illness, which is less available in these patients. We are also aware of this phenomenon in patients with congestive heart failure (especially those who are elderly), and we are now also examining stroke patients.”

As to the practical significance of the findings, says Prof. Amir, “In our humble opinion, the concept that lower BMI is essential for a healthier coping ability with acute or chronic illness is not necessarily correct. However, it should still be noted that an excessively high BMI, as happens with extreme overweight, is also not recommended from a medical point of view, and survival following a heart attack is lower among them as well. Moderate overweight seems to be probably the healthiest for dealing with at least some heart disease.”

The article was published in the Vascular Health and Risk Management journal.

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