Scientists already know that stomach fat — known as abdominal obesity — increases the risk of having a first heart attack. But new research finds that having excessive fat in this specific area also increases risk of subsequent heart attacks.
“The reason abdominal obesity is very common in people with a first heart attack is that it is closely linked with conditions that accelerate the clogging of arteries through atherosclerosis,” explains study author Dr. Hanieh Mohammadi, from the Karolinska Institute in Stockholm, Sweden.
“These conditions include increased blood pressure, high blood sugar, and insulin resistance (diabetes) as well as raised blood lipid levels.”
However, Dr. Mohammadi says the team’s results “suggest that there may be other mechanisms associated with abdominal obesity that are independent of these risk factors and remain unrecognized.”
Although a relatively understudied area, the link between stomach fat and recurring heart attacks was so distinct that the study’s authors believe that healthcare professionals should use waist circumference to identify at-risk patients.
The research, published in the European Journal of Preventive Cardiology, did not just look at recurrent heart attacks, but also at ischemic strokes and coronary heart disease death that occurred after an initial heart attack.
The study involved more than 22,000 participants aged 35–77, making it the largest study on the topic, to date. The Swedish team enlisted people from the country’s SWEDEHEART cardiac registry. Almost 17,000 were male.
The researchers followed each participant for around 4 years after their heart attack. The team used the data from the participants’ initial hospital visits and further check-ups.
The first follow-up visit took place between 4 and 10 weeks after the person had a heart attack, and the second took place between 12 and 14 months after the cardiovascular incident.
During these visits, the researchers identified cardiovascular risk factors via a standardized survey.
The researchers measured the participants’ waist circumferences along with weight, height, blood pressure, electrocardiogram (ECG) rhythm, and levels of blood lipids and glucose.
They calculated waist circumference — the main focus of the research — by measuring the stomach between the last rib and the iliac crest, which is the most prominent part of the pelvis.
Independent researchers associated abdominal obesity with both fatal and non-fatal heart attacks and strokes, even when they took other cardiovascular risk factors, such as smoking and blood pressure, into account.
In fact, the team concluded that stomach fat was a more vital indicator of recurrent heart attacks than general obesity.
The majority of the study’s participants exhibited abdominal obesity (78% of men and 90% of women). The researchers defined obesity in this area as a circumference of 94 cm or more for males and 80 cm or more for females.
Secondary prevention treatments also had no effect on the relationship between stomach fat and recurrent cardiovascular incidents; a finding that was “previously unknown,” according to Dr. Mohammadi.
Doctors typically give secondary prevention treatments to patients “after their first attack to prevent second events,” Dr. Mohammadi says. These treatments work “by reducing risk factors associated with heart attack and stroke, such as high blood sugar, lipids, and blood pressure.”
“In our study,” Dr. Mohammadi continues, “patients with increasing levels of abdominal obesity still had a raised risk for recurrent events despite being on therapies that lower traditional risk factors connected with abdominal obesity — such as anti-hypertensives, diabetes medication, and lipid lowering drugs.”
As well as being the first study to find that secondary prevention treatment has no effect on recurrent risk if abdominal obesity is present, the research is also the first to analyze by sex.
When examined separately, males and females demonstrated certain differences. The link between waist circumference and subsequent heart attacks was stronger in men, for example.
But, in females, the lowest risk did not mean having the smallest waist circumference. Instead, it was the mid-range circumference that decreased a female’s risk of recurrent events.
Dr. Mohammadi has a theory: “Some studies have suggested that abdominal obesity may be more directly associated with the evil visceral fat (fat that sits around your organs) in men compared to women.
“In women, it is thought that a greater portion of the abdominal fat is constituted by subcutaneous fat, which is relatively harmless.”
These differences, however, need further examination as “there were three times as many men in the study compared to women, contributing to less statistical power in the female group.”
Despite this, the conclusion is still clear, explains Dr. Mohammadi.