Declining Fitness Over a Decade Doubles Risks of AMI (heart attack)

Medscape Medical News from the:

• American Heart Association (AHA) 2012 Scientific Sessions

Shelley Wood    –    Nov 04, 2012  Heartwire Medical Journal

LOS ANGELES — Finnish men who lost more than 15% of their cardiorespiratory fitness over a 10-year period faced a near doubling of their risk of acute MI over the subsequent decade and more than twice the risk of dying of any cause, a new study shows.

Dr Jari A Laukkanen (University of Eastern Finland, Rovaniemi, Finland) presented 10-year results from the ongoing Kuopio Ischemic Heart Disease Risk Factor Studyhere at the American Heart Association 2012 Scientific Sessions.

In clinical practice, physicians “usually measure the risk factors that are easy to treat,” Laukkanen told heartwire . “But even after taking into account the usual risk factors–lipids, BMI, smoking, BP, diabetes, and alcohol consumption–still there was a risk related only to fitness, and it should be [given] more importance.”

The Kuopio study enrolled an unselected population of 2682 men between the ages of 42 and 60 that Laukkanen described as a mix reflective of the broader population–most of the men had no CVD at baseline, but some had preexisting CAD.

All men participated in a baseline exam in the late 1980s that included a respiratory gas analyses and electrocardiogram during exercise testing. Of the original cohort, 585 men underwent repeat testing 11 years later. During this initial study period, fitness levels declined, on average, by 5.2 mL per kg/minute of VO_2max (equal to 1.9 METs change). Previous studies have suggested that levels of cardiorespiratory fitness typically decline at a rate of 5% to 15% per decade between the ages of 20 and 80 years, Laukkanen noted.

Staying Fit, Staying Alive

In the Kuopio study, the average follow-up time beyond the second exercise test was 10.9 years. During this follow-up period, study subjects had a total of 81 acute MIs, and 92 subjects died. When analyzed according to change in fitness levels, a loss of more than 15% of baseline cardiorespiratory fitness over 10 years was associated with an 88% increased risk of AMI and a 122% increased risk of total mortality, after adjustment for age and other risk factors. The results remained statistically significant after taking baseline VO_2max into account.

The investigators also showed a dose-response with declining exercise: for every 1-MET decrease in VO_2max, the risk of all-cause death increased “by a constant proportion,” Laukkanen said.

“VO_2max can be used as a very powerful predictor of AMI and all-cause death beyond that predicted by many conventional risk factors.” Laukkanen and colleagues concluded. “The main public-health message is that it is very important to maintain the level of cardiorespiratory fitness to prevent a premature death from all-causes.”

What’s Good for the Gym . . . 

To heartwire , Laukkanen said that he does not routinely measure VO_2max in clinical practice unless there is a reason for performing exercise testing, and current guidelines do not support routine measurement of cardiorespiratory fitness in healthy patients. But his study provides some rationale for performing more exercise tests in the future: it is inexpensive, noninvasive, and easy to perform in the clinic, he said.

“I think many of us are interested in measuring our fitness level–for example, you can go to a gym and take the test, and it’s quite easy to measure. But for some reason, it is a different topic to talk about measuring your fitness level in the gym than [measuring it] at the doctor’s office.”

Other studies have suggested that people–even doctors–tend to overestimate their fitness level.

His study also provides an oft-repeated reminder to physicians that urging their patients to become fit or maintain their fitness does have measurable benefits on cardiovascular health and longevity. And taking the time to measure fitness in practice, even just to establish a benchmark, may prove helpful in preventing future disease, he added.

Laukkanen and colleagues had no conflicts of interest.