Saturday, March 7, 2015

This Test Could Predict Your Death — Would You Pass?

Hop on your nearest treadmill and get running with this simple death test. (Photo: Getty Images) 

Want to make sure you’ll be around in 10 years? Hop on a treadmill: After analyzing 58,000 stress tests, Johns Hopkins researchers determined — with great accuracy — that the results of a treadmill test could predict risk of death over a decade.

In the study — while being watched by professionals — people who were heart disease-free, but referred for an exercise stress test completed a treadmill test called the Bruce Protocol.

And while this wasn’t tested in a general population, the Bruce Protocol formula is valid:

“We could assume that in people with no symptoms, this treadmill test would at least predict the level of survival over a decade,” Haitham Ahmed, MD, MPH, and lead author of the study tells Yahoo! Health.

Calculating your own score.

So how exactly is it done?

 The test consists of three-minute segments that increase in speed and incline.

In the study, people exercised until they were fatigued, felt chest discomfort, or until a clinician saw something suggesting lack of blood flow to the heart, says Ahmed.

Below is an example of the stages of incline and speed from the Bruce Protocol: 

Stage 1        1.7 mph/10% grade/5 METs 
Stage 2        2.5 mph/12% grade/7 METs
Stage 3        3.4 mph/14% grade/10 METs
Stage 4        4.2 mph/16% grade/13 METs
Stage 5        5.0 mph/18% grade/15 METs
Stage 6        5.5 mph/20% grade/18 METs
Stage 7        5.5 mph/22% grade/20 METs

In addition to accounting for age and sex, the formula used in the study factored in how well you tolerate exercise — measured in “metabolic equivalents” or METs, says Ahmed.

This tells you how much energy you’re expending while working out. (More vigorous exercise means higher METs.)

“The longer you can stay on, the more METs you accrue,” he says, noting that the median MET score was 10.

“More than 10 METs was associated with a higher fitness level and good survival rate.”

Then, researchers used the following formula:

(12 x METs) + (% of maximum predicted heart rate) – (4 x age) + 43 if female.

*Maximum predicted heart rate is calculated as 220 – age. Heart rate achieved during exercise should be divided by maximum predicted.

 For example, if you’re 20 years old, your maximum predicted heart rate is 200 (220 – 20). If you achieve 180, you achieved 90 percent of maximum.

You want a positive score. If you have at least zero, your survival rate is 97 percent in the next decade, says Ahmed.

In the study, scores ranged from negative 200 to positive 200.

“People 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,”researchers noted.

“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.” 

Why fitness matters.
Of all the parameters measured, METs and fitness levels were the strongest predictor of whether a person would live or die, even after accounting for family history, disease, and health habits, says Ahmed.

 “After fitness, age, and gender, almost nothing else mattered or improved survival.” 

How come? The answer lies in what we know to be true: the vast power of exercise, he says. “We understand a lot about fitness. And while there is still a lot to learn, we know that usually, those who exercise more often have lower obesity rates, lower blood pressure, lower risk of diabetes, a reduced risk of blood clotting, reduced inflammation, and lower levels of bad cholesterol.”

The good news:
In a pricey world of medical testing, medications, and gym memberships, cardio is a free way to add years to your life. 

“We have come into an age where medical testing is expensive,” says Ahmed.

“This is a score that costs nothing—it is virtually free besides the treadmill.”

And if you’re not happy with your fitness levels, there’s room to grow: “Today, we think of standard stress tests in terms of ‘pass’ and ‘fail’, but that’s an outdated way to think of risk.”

Just like you can develop heart disease over years, so too can you build fitness. It’s a spectrum, he says.