The Cooper Institute
 

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH

 
 
 

Does fitness further reduce the risk of heart disease deaths among individuals who are already at low risk?

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Wednesday, Feb 24, 2021

Moderate to High Levels of Fitness Decrease Heart Disease Death Risk Even Among ‘Low Risk’ Individuals! The Cooper Center Longitudinal Study


Although cardiovascular disease (CVD) has been the leading cause of death in the U.S. for over a century, the causes of CVD were completely unknown until the early 1960s. In fact, heart attack and stroke were thought by many to be a natural consequence of the aging process!

In the mid-1940’s, Dr. William Kannel boldly suggested that CVD might be related to certain health behaviors. However, he had no hard data to support his opinion. Dr. Kannel was able to convince the National Heart Institute (now known as the National Heart, Lung, and Blood Institute, or NHLBI) to launch the now world-famous Framingham Heart Study in 1948.

Framingham Heart Study physicians in 1948, the year the landmark study started in the Massachusetts town. (Public domain)
Framingham Heart Study physicians in 1948, the year the landmark study started in the Massachusetts town.
(Public domain)

Residents of Framingham MA were invited to participate in a lifelong research project where they would receive free comprehensive medical exams every two years, for as long as they lived in Framingham. In exchange for these free exams, subjects agreed to have their medical records included in a large database, and to be tracked for morbidity (illness) and mortality (death). As the data began to accumulate, scientists noticed that people with certain health behaviors and characteristics were more likely to die from heart attacks and strokes than people without those same behaviors and characteristics.

Today, these are known as ‘risk factors.’

The major CVD risk factors include:

  • Abnormal blood cholesterol level
  • Hypertension
  • Cigarette smoking
  • Obesity
  • Diabetes
  • Family history
  • Age
  • Sedentary lifestyle

By 1998, the Framingham Risk Score (FRS) had been developed; FRS estimates an individual’s 10-year risk for a future cardiovascular event (e.g., heart attack and stroke) based on their current risk factors. This assumes that they have not had a heart attack or stroke in the past. If the 10-year risk is less than 10%, then the individual is deemed ‘Low Risk’. The Low Risk group comprises a substantial proportion of U.S. adults; with more than 100 million individuals categorized as such.

Over the past 50 years, researchers at The Cooper Institute have consistently shown that cardiorespiratory fitness level (CRF) is a powerful risk factor for CVD and other types of morbidity and mortality. Because CRF is not part of the Framingham Risk Score or more recent risk algorithms, Cooper researchers wanted to determine whether or not a ‘Low Risk’ individual’s level of CRF added to the predictive value of the FRS.

Accordingly, 11,190 Low Risk Cooper Clinic men and women with an average age of 41 years underwent a maximal treadmill stress test during their comprehensive physical exam. Subjects were categorized as being low fit if they scored in the bottom 20% compared to others of their same age group and gender. Subjects scoring in the next highest 40% were categorized as being moderately fit, while those scoring in the highest 40% were categorized as being high fit.

The group was then followed for an average period of 27 years; during which time 214 patients died from CVD. The CVD death rate across CRF categories is shown in the Figure below. Compared to low fit subjects, men and women who were moderately fit were about 40% less likely to die from CVD. High fit men and women were about 65% less likely to die from CVD than those who were low fit. Remember that while all of these men and women were categorized as ‘Low Risk’ based on the FRS at the time of their exam, the FRS does not take CRF into account.

The take-home message is that while it’s still very important to control traditional risk factors like blood pressure, blood cholesterol and glucose, body weight, and tobacco use, it’s not enough to get your CVD risk as low as it can be.
 

Individuals must also achieve a moderate, or preferably a high level of CRF in order to minimize risk as much as possible. Achieving a moderate level of CRF is well within the reach of most adults who meet the public health guidelines for physical activity (accumulate 150 minutes or more of moderate intensity aerobic activity each week). In order to reach a high level of CRF, it’s very likely that individuals will need to include some vigorous intensity aerobic activity as well.

The next time you have a comprehensive physical exam, ask your physician for your Risk Score. In recent years, the FRS has been replaced by a newer risk algorithm called the Atherosclerotic Cardiovascular Disease (ASCVD) Risk Estimator. It’s available as a free app; or, here is the link if you prefer to go that route: cvriskcalculator.com.

Keep in mind that even if the results show that you are in a ‘Low Risk’ category, you can further decrease your risk of a cardiovascular event by achieving a moderate or high level of cardiorespiratory fitness!  


References 
Wilson, P. W. (1998). Prediction of coronary heart disease using risk factor categories. Circulation, 97:1837-1847.  

Barlow, C. E., DeFina, L. F., Radford, N. B., Berry, J. D., Cooper, K. H., Haskell, W. L., Jones, L. W., Lakoski, S. G. (2012). Cardiorespiratory fitness and long-term survival in ‘low risk’ adults. J. Am. Heart Assoc, Aug;1(4):e001354. doi: 10.1161/JAHA.112.001354.1:e001354