Live longer -- exercise until you drop

Even in the most decrepit patients with serious heart
problems, exercise extends life

By Owen Dyer

"First, do no harm" is a saying often attributed to Hippocrates, the father of medicine. The sentiment remains a cornerstone of modern medical ethics, and with the growth of litigation it's more pertinent now than ever before.

So it's hardly surprising that physicians are nervous about recommending exercise for patients with advanced cardiovascular diseases. Yet research has shown repeatedly that among even the most fragile patients, carefully managed exercise can bring improvement in a range of chronic conditions, from multiple sclerosis to osteoporosis.

Cardiovascular disease presents a special problem, because too much physical strain could provoke a heart attack, yet these patients clearly stand to benefit from physical activity if they can stand it. A study in the British Medical Journal set out to measure the effect of exercise programs on patients suffering from heart failure due to left ventricular systolic dysfunction.

Rather than subject a large group of patients to a potentially risky treatment, the investigators reviewed nine previous small studies and analysed their combined results to achieve greater statistical power in their findings. A total of 801 patients were included in these studies, of whom half followed exercise programs and half acted as controls. Eight of the studies were European while the ninth and biggest was Canadian.

LONGER LIFE SPAN
The patients in these studies were, to put it bluntly, at death's door. The primary outcome measurement was therefore time to death from all causes, with a secondary endpoint of either death or admission to hospital. Overall, there were 88 deaths in the exercise arm, with a median time to the event of 618 days. In the control arm, 105 patients died, with a median time to the event of 421 days. This translates to a mortality hazard ratio for the exercise group of 0.65, which means, in essence, that patients with chronic heart failure who exercise can expect, on average, to live 50% longer than those who do not.

The secondary end point of death or hospitalization occurred in 127 patients in the exercise arm and 173 in the control arm, with an average time to the event of 426 days and 371 days respectively. This produces a hazard ratio of 0.72 for the exercise group.

The researchers divided the patients into subgroups to see if any particular class of patient benefited more than others. They considered age, gender, ischemic or non-ischemic disease, New York Heart Association classification, left ventricular ejection fraction, peak oxygen uptake, renal function and medication. None of these factors appeared to have any significant influence on results, suggesting that all heart failure patients stand to gain from exercise.

The actual mechanism by which exercise prolongs life in these patients is unclear. One explanation, suggested the authors, "is that exercise training improves myocardial perfusion by alleviating endothelial dysfunction and therefore dilating coronary vessels and by stimulating new vessel formation by way of intermittent ischemia." In dogs, exercise training raises the ventricular fibrillation threshold.

A study on exercise capacity and mortality among men, published in 2002 in the New England Journal of Medicine, found that exercise capacity, even if assessed without metabolic measurements, is a more powerful prognostic indicator than traditional risk factors such as smoking, high blood pressure, blood cholesterol level and diabetes.