Heart Week 2001: Get active! A call to action

The evidence

• Much of the epidemiological evidence relates to primary prevention and comes from good-quality observational (cohort) studies. The better-designed studies show stronger relationships and a dose-response relationship between inactivity and CHD; the benefits of increasing activity levels accrue particularly for people who have been inactive.¹

• Evidence from meta-analyses suggests that people who remain sedentary have about twice the risk of CHD of those who participate in regular activity.³ Replication studies in diverse populations since 1990 have reinforced this evidence.

• There is consistent evidence that women benefit almost as much as men from regular, moderate-intensity physical activity, as do older adults.^4,5 It appears that only recent or current physical activity is beneficial, rather than athleticism in earlier life.⁶ For all age groups, adopting physical activity reduces the risk of CHD deaths, leading to the maxim that "it is never too late to start being active".^5,7

• Some of this cardiovascular benefit occurs even at levels of physical activity below those required for aerobic (fitness or cardiorespiratory) training, at levels as low as 50% of the maximal predicted heart rates for age.^1,8 However, for the general population, more vigorous activity results in additional benefits.

• There is also evidence that physical activity may prevent ischaemic stroke.⁹ The mechanism may be through reducing the risk of thrombus formation, or the effects of physical activity may be mediated through reducing blood pressure levels.

• These protective effects reducing the incidence and mortality from CHD are independent of the influence of physical activity on other cardiovascular risk factors. Nonetheless, there are direct benefits on other risk factors, with moderate activity contributing to lowered blood pressure, increased high density lipoprotein (HDL) cholesterol level, and improvements to the fibrinolytic system.^1,8 More sustained physical activity may also help with weight loss.

• Physical activity has similar benefits for many patients with established coronary artery disease. In those who become active, these benefits include increased fitness, improved oxygen consumption, and decreases in ischaemic responses.⁸

Biological mechanisms: Researchers have begun to explore the biological mechanisms to explain the benefits of physical activity in preventing CHD. There is controlled-trial evidence that sustained vigorous activity can lead to some regression of atherosclerosis.^8,10 Exercise may improve coronary endothelial-dependent vasodilatation responses, possibly leading to recruitment of collateral vessels in ischaemic heart disease.¹¹ However, further work is needed to define the exact biological mechanisms. For patients with CHD, there is clinical evidence of increased functional capacity and improved myocardial perfusion after exercise training, and there may even be some benefits for those with uncomplicated heart failure.⁸

Cardiac rehabilitation: Although the benefits of cardiac rehabilitation are generally accepted,¹² these are multifaceted programs, and the individual benefits of the exercise component are difficult to disentangle from the overall program benefit. The key issue here is that, after myocardial infarction, a much higher proportion of patients in Australia need to complete supervised rehabilitation programs than is currently the case.

Risk of acute cardiac events: One well-known paradox is the issue of the increased risk of acute cardiac events in unfit sedentary people who embark on vigorous exercise regimens.¹³ Although the risk of sudden cardiac events is transiently increased (during and for a half hour after strenuous exertion), this acute increment in risk is much reduced for moderate activity. Overall, even among CHD patients, the long term benefits of activity vastly outweigh the short term risks. Furthermore, it has been shown that the overall risk for primary cardiac arrest is much lower among those who are moderately active.¹⁴ Thus, among cardiac patients, vigorous activity should be started with caution and in supervised settings, whereas moderate physical activity should be easier to initiate.

In conclusion, almost half of Australian adults do not achieve the health goal of moderate participation in physical activity. Recent trends have shown that physical activity levels are declining (as obesity rates are increasing), and that women, those least advantaged and non-English speakers are more likely to be inactive.¹⁵ There is a clear mandate to include physical activity advice in consultations, especially for those at risk of heart disease. Brief advice about activity, delivered in the surgery, can positively influence physical activity levels.¹⁶ Adherence to structured activity programs is poor, so that constant reinforcement is useful, as well as recommending types of activity which can become part of everyday life. Some patients will be very active, but still develop CHD. However, on balance, increasing activity is a worthwhile investment of medical practitioners' time. For Heartweek 2001, go for a regular walk, and recommend it to almost every patient!

Adrian E Bauman
Professor of Public Health and Epidemiology
School of Community Medicine
University of New South Wales, Sydney, NSW

Terry J Campbell
Professor of Medicine
University of New South Wales
(St Vincent's Hospital), Sydney, NSW

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