By studying a large cohort of women who had already been through menopause, researchers have found that cardiovascular risk is associated with body shape, which results from how fat is distributed in the body.
However, new research, from the Albert Einstein College of Medicine, in New York, NY, and other institutions, points to another potential factor, namely, where fat is stored in the body — for women over the age of 50, at least.
The new study — the findings of which appear in European Heart Journal — has looked at data from 161,808 women aged 50–79 to find out whether BMI or fat distribution was associated with cardiovascular risk.
All of the participants had enrolled in the Women's Health Initiative between 1993 and 1998. Follow-up information on the participants' health was available from that period to the end of February 2017.
None of these women had cardiovascular disease at baseline. Throughout the study period, however, the researchers recorded 291 new cases of cardiovascular disease.
Body shape matters
In the study, the investigators measured body fat mass through dual-energy X-ray absorptiometry, a type of scan that assesses a person's fat, muscle, and bone density.
The team found a pattern. Women with the highest percentage of fat stored around their middles and trunks and the lowest percentage of fat around their legs, giving them an "apple" body shape, also had the highest risk of cardiovascular disease.
These women had more than thrice the risk of cardiovascular disease of peers with a low percentage of fat around their middles and a higher percentage of fat around the legs: the "pear" shape.
Moreover, women in the top 25th percentile with the most body fat around their middles had almost double the risk of experiencing heart problems or a stroke, compared with the top 25% of women with the least body fat around their middles.
At the same time, women with the most fat around their legs had a lower risk of cardiovascular disease — 40% lower than those who had the least amount of fat around their legs.
Yet, the researchers add, body weight seems not to affect this risk.
"Our findings suggest that postmenopausal women, despite having normal weight, could have varying risk of cardiovascular disease because of different fat distributions around either their middle or their legs. In addition to overall body weight control, people may also need to pay attention to their regional body fat, even those who have a healthy body weight and normal BMI," says lead author Qibin Qi, Ph.D.
Furthermore, the investigators argue that reducing the amount of midriff body fat alone could help reduce the risk of cardiovascular disease.
Thus, by looking at the women who did not change their amount of leg fat during the study period but who reduced the proportion of middle fat — from over 37% to under 27% — the researchers calculated that, among 1,000 participants, around six cases of cardiovascular disease per year could be prevented.
They estimated a similar outcome for women who do not lose any midriff fat but who increase the proportion of leg fat: Among 1,000 women who increase leg fat from under 42% to over 49%, around three cases of cardiovascular disease per year could be prevented, the researchers found.
A need for better assessments
However, Qi warns, these associations may not apply to everyone.
"It is important to note that participants of our study were postmenopausal women who had relatively higher fat mass in both their trunk and leg regions. Whether the pattern of the associations could be generalizable to younger women and to men who had relatively lower regional body fat [levels] remains unknown," he says.
At the same time, the researchers believe that their current findings make a good case for using measurements other than just BMI when considering the risk of cardiovascular disease.
"In routine clinical practice, BMI is a common approach to assessing a person's risk of cardiovascular disease. Measurement of waist circumference is also recommended by [a] national organization to provide additional information, but usually only in those with a BMI between 25 to 34.9 [kilograms per square meter]," explains Qi.
"As such," he adds, "some people who are categorized as [having] a normal weight may not be recognized as being at increased risk of cardiovascular disease due to the distribution of their body fat, and so may not have preventive measures recommended for them."
"Our findings highlight the need for using anthropometric measures that better reflect regional fat distribution to identify increased risk of cardiovascular disease. These are important research directions for future population studies."
Qibin Qi, Ph.D.