BMI vs. BRI: Why body roundness may be a better indicator of heart disease risk

Body mass index (BMI) measures a person’s height and weight and helps identify overweight or obesity. However, BMI does not differentiate between fat mass and muscle, so it’s not the only component doctors use to determine health risks.

Cheng-Han Chen, MD, a board certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, who was not involved in the study, explained some of the limitations of BMI to Medical News Today:

“While relatively simple to use, the body mass index has many flaws that limit its ability to assess a person’s health status. Most importantly, it does not account for body fat content and distribution, and does not account for muscle and bone mass. In addition, it does not account for racial, ethnic, and sex differences. These many limitations make BMI a relatively poor indicator of physical health.”

One additional measurement that may be helpful is body roundness index (BRI). As noted by the authors of the current study, BRI looks at waist circumference and height and helps reflect fat proportion in the body.

Mir Ali, MD, a board certified bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, who was also not involved in the study, noted the following to Medical News Today:

“Body roundness index is based on waist circumference and height. It has been shown in other studies that increased abdominal fat is a risk factor for other adverse health conditions such as diabetes and hypertension. If a patient has an increased body roundness index, then further investigation may be warranted to look for occult cardiovascular disease. Like other screening tools it has limitations, but still can be useful.”

The current researchers wanted to examine the relationship between BRI trajectories and cardiovascular disease risk.

This research included middle-aged and older Chinese participants in the China Health and Retirement Longitudinal Study. In total, researchers were able to analyze data from 9,935 participants. They excluded individuals who already had cardiovascular disease or who had missing BRI data at baseline. The average age of participants was about fifty-nine years old.

The researchers had data from blood samples, blood pressure, and BRI. They also had baseline data on lifestyle risk factors. They looked at BRI and the incidence of stroke and cardiac events.

In their analysis, researchers looked at BRI trajectories, or the course of BRI over time, using models that corrected for different covariates. For example, researchers were able to take into account medical and medication history.

The researchers divided participants into three BRI trajectory categories: low-stable, moderate-stable, and high-stable. They noted that participants in the high-stable BRI category were more likely to have certain characteristics like high blood pressure, diabetes, and increased age. They were also more likely to be male but less likely to smoke or drink.

From 2017 to 2020, there were just over 3,000 cardiac events documented and 894 recorded deaths.

Overall, researchers found that the moderate-stable and high-stable BRI trajectory groups were at a higher risk for cardiovascular disease compared to the low-stable BRI trajectory group.

In their crude model, the moderate-stable group had a 61% increased risk for cardiovascular disease compared to the low-stable group, and the high-stable group had a 163% increased risk. After adjusting for variables, researchers still observed an increased risk for cardiovascular disease in the moderate and high BRI trajectory groups.

They found that the moderate-stable group had a 29% increased risk for stroke and a 14% increased risk for cardiac events compared to the low-stable group. The high-stable group had a 46% increased risk for stroke and a 35% increased risk for cardiac events compared to the low-stable group.

They also found that considering BRI trajectory helped with cardiovascular disease risk reclassification.

The results indicate that having BRI increase for a prolonged period increases the risk for cardiovascular disease and that it may be helpful to take BRI into account to better prevent cardiovascular disease.

This research does have limitations. First, this study focused on Chinese participants who were middle-aged and older adults, so studies with greater diversity may be necessary to confirm the findings. It also means the results may not be generalizable to other groups.

The researchers acknowledge that the study time frame might have been insufficient, so more long-term studies may be helpful. In addition, the high-stable BRI trajectory group accounted for just under 8% of the study population, which could have affected the results.

Some of the data was participant-reported. Particularly, the cardiovascular disease diagnosis was from self-reported physician assessments. The study authors acknowledge that this self-reporting of cardiovascular disease could cause information bias.

The researchers were also only able to focus on cardiovascular disease because they were unable to look at causes of death, which could be helpful in future studies. Finally, the study authors acknowledge the possibility of unmeasured bias and bias from unaccounted factors. They agree that future research can help confirm their findings.

Despite these limitations, the data does present the potential benefits of using BRI as a health indicator.

BMI or BRI?

“By taking into account waist circumference as well as height, this metric better reflects the distribution of fat in the body than BMI does. As such, it should be better able to provide information on an individual’s health risk and indicate when intervention would be recommended to help reduce the risk. This study found an association between higher body roundness index (BRI) and increased risk of developing cardiovascular disease. This is a useful finding that might lead to wider adoption of BRI as a tool to help assess an individual’s heart disease risk.”
— Cheng-Han Chen, MD