Researchers at the Mayo Clinic have devised a simple treadmill test and formula to calculate your odds of surviving the next ten years, and it goes like this: FIT Treadmill Score = %MPHR + 12 (METS) - 4 (age) + 43 (if female). Here's how it works and what it means to your health.
"The notion that being in good physical shape portends lower death risk is by no means new, but we wanted to quantify that risk precisely by age, gender and fitness level, and do so with an elegantly simple equation that requires no additional fancy testing beyond the standard stress test," noted team leader Haitham Ahmed of Johns Hopkins University School of Medicine in a statement.
To create this algorithm, Ahmed's team studied 58,020 adults from Detroit aged 18 to 96 who were being evaluated for chest pain, shortness of breath, fainting, or dizziness (all of the participants were free from established heart disease). These individuals were put through exercise stress tests from January 1991 through to May 2009.
For the test, participants exercised on a treadmill at increasing speed and incline. While they were exercising, the researches measured peak heart rate (%MPHR) and their ability to withstand physical exertion. On that latter point, they measured metabolic equivalents, or METs, which gauges how much energy the body expends during exercise. The more intense the exercise, the higher the METs (e.g. slow walking = ~2 METs, whereas running = ~8 METs).
In addition, the researchers collected data as it pertained to test subjects' age and mortality. Once all the data was in, statistical models were used to identify the test variables most predictive of survival. They found that, among people of the same age and gender, fitness level was the single most powerful predictor of death, i.e. "all cause mortality," and survival. This continued to be the case even after accounting for such conditions as diabetes and a family history of premature death.
Here's the formula they came up with:
FIT Treadmill Score = %MPHR + 12 (METS) - 4 (age) + 43 (if female)
Yes, women live longer than men, hence the 43 bonus points.
The Mayo Clinic explains how the results of the formula are to be read:
Scores ranged from negative 200 to positive 200, with those above 0 having lower mortality risk and those in the negative range facing highest risk of dying. Patients who scored 100 or higher had a 2 percent risk of dying over the next 10 years, while those with scores between 0 and 100 faced a 3 percent death risk over the next decade. In other words, two of 100 people of the same age and gender with a score of 100 or higher would die over the next decade, compared with three out of 100 for those with a fitness score between 0 and 100. People with scores between negative 100 and 0 had an 11 percent risk of dying in the next 10 years, while those with scores lower than negative 100 had a 38 percent risk of dying.
Put another way, scores between 100 and 200 means a person has 98% assessed probability of surviving the next ten years, while a score between -100 and -200 suggests a person has a 62% chance of surviving.
As an example, a 45-year-old woman with a fitness score in the bottom fifth percentile has an estimated 38% risk of dying over the next decade, compared with 2% for a 45-year old woman with a top fitness score.
That's a shocking difference — one that points to the importance of regular exercise and cardiovascular health. It also suggests that you may want to up the intensity level at the gym.
"In medicine we usually base predictions of survival on the absence or presence of a disease state," noted ABC News medical contributor Dr. Jennifer Ashton. "What's new here is that there is now a fancy equation doctors can use to compare the chances of survival for one 50-year-old woman against another 50-year-old woman."
It's obviously important to take a study like this with a grain of salt and not panic if your odds are uncomfortably low. This algorithm is not destiny. Moreover, as noted by the study's authors, regular exercise can influence your results.
You may also not want to evaluate yourself. As noted by Melissa Healy in the LA Times, "Do-it-yourself stress testing is probably not very reliable, since a physician or sports physiologist needs to be around to decide when to call a halt to the test (and therefore what maximum a test-taker has achieved)."
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