New Study Published by PLC’s Dr. John Rumberger et al Evaluates How Your BMI Relates to Actual Cardiovascular and Total Mortality
By John A. Rumberger, PhD, MD, FACC, FSCCT
Director of Cardiovascular Imaging
BMI [body mass index] is a convenient and easily calculated index of overall body ‘fat’ and thus is used in many clinical situations [and other situations such as part of the physical examination for life insurance] as an index of obesity. Generally this is classified as ‘underweight’ [BMI <18.5], ‘normal’ [BMI 18.5 to 24.9 ], ‘overweight’ [BMI 25 to 29.9], and ‘obesity’ [BMI of >30]. The BMI is easily calculated from an individual’s height and weight (a simple calculator for you to use is found at the National Heart, Lung & Blood Institute) or simply BMI = (weight in pounds x 703)/ (height in inches x height in inches). In the United States it is estimated that two thirds of the general population are either overweight or obese.
Why do we care about measuring the BMI? In general, it has been shown in numerous studies that the higher your BMI the higher the risk for developing diabetes, having arthritis, developing liver disease [most common ‘fatty liver’], increase risk of several types of cancers [such as breast, colon, and prostate], developing high blood pressure, having high cholesterol, and having sleep apnea. Another important ‘risk’ of increasing BMI is heart and cardiovascular disease.
The question however is: ‘how does the BMI relate not to ‘risk’ but actual cardiovascular and total mortality’.
Coronary artery calcification [CAC] ‘score’ using non-contrast CT of the heart has been established as likely the best individual ‘risk factor’ for the subsequent development of heart disease [angina, heart attack, sudden cardiac death] – over and above other ‘risk factors’. This evaluation is done on ALL patients seen at the Princeton Longevity Centers [Princeton, NJ; Fairfax, VA and Shelton, CT].
I personally have been involved with CAC research beginning in the early 1990’s and have published multiple papers in the field. Several years ago I along with colleagues at John’s Hopkins, UCLA, University of Minnesota, and Cornell Medical Center started the ‘CAC Consortium’ bringing results from 66,000 individuals who had NO known heart disease at baseline but had CAC scans done in the 1990’s and early 2000’s and had been followed for subsequent cardiac and all-cause mortality for, on average, 12 years.
Our latest published paper in the AHA journal Cardiovascular Imaging [2020, volume 13, issue 7] deals with the association of BMI with CAC and subsequent cardiovascular mortality.
A total of 36, 509 individuals from the CAC Consortium, mean age 54 years, 1/3 women, and median BMI of 26.6 were included in the analysis and followed up a mean of 11.4 years. In general, the presence of conventional cardiovascular disease risk factors [high cholesterol, family history of heart disease, diabetes, current smoking, and hypertension] increased across categories of BMI – with the highest risk in smokers and those with family history of heart disease [interesting, although smoking is considered a major ‘risk factor’, we found that having a family history of premature heart disease (parent or sibling with heart disease younger than 55 years) to be FIVE times the risk of smoking].
Due to the size of the sample we were able to also study the relationship between initial CAC score and BMI in both men and women. An adaptation of that relationship is show in the figure below:
As can be seen from the figure: the higher the individual’s BMI at baseline, the higher the association of positive CAC scores, in both men and women.
In comparison to those with normal BMI – those with obesity at baseline had a 60% excess risk of developing heart disease or stroke, and 30% excess all-cause mortality. However, there was no excess risk identified in those ‘overweight’ compared to ‘normal’ BMIs.
In conclusion, this large sample study with >11 years follow up showed a clear association between BMI and finding evidence for coronary artery calcification [and thus atherosclerotic plaque]. But in terms of subsequent risk of coronary heart disease, cardiovascular disease, and all-cause mortality this was found to be excessive only in ‘obese’ men and women but not in those that were ‘overweight’ by BMI. Thus working to avoid a BMI >30 can have a major impact on increasing your Longevity by lowering your subsequent heart/stroke and all-cause mortality.