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Melbourne, VIC, Australia
Dr. Worsnop is a Respiratory and Sleep Physician, Austin Hospital.
Correspondence to: Christopher J. Worsnop, FCCP, Department of Respiratory and Sleep Medicine, Bowen Centre, Austin Campus, Austin Hospital, Heidelberg, VIC, 3084, Australia; christopher.worsnop{at}austin.org.au
There was a time when asthmatics were regarded as chronically infirm individuals who needed to be protected and sheltered, particularly from physical exertion, lest they succumb to a severe asthma attack. Children were prevented from playing sport at school, and adults led inactive lives. Times have changed. The modern management of asthma, including the wide variety of drugs and delivery devices that we have available, allergy avoidance measures, patient education, and asthma action plans, now mean that our perception of asthmatics and our goals of treatment have changed. The long-term aims of asthma management include the minimization of symptoms so that asthmatics can lead normal lives, with the achievement of the best quality of life for the asthmatic. The National Asthma Council in Australia summarizes these goals in its Asthma Management Handbook when it says that, "Most people with asthma lead normal lives and can participate competitively in sport."1
In view of this modern approach to asthma, it is both heartening and disheartening to read the article by Ford et al in this issue of CHEST (see page 432). They report the results of a survey of > 165,000 adults in the United States, of whom 12,500 were current asthmatics, and nearly 5,000 were previous asthmatics. They found that a similar proportion of current asthmatics, previous asthmatics, and those who had never had asthma were inactive. The same proportion in each group, just under one fourth, participated in physical activity or exercise for at least 150 min per week. In one way, these results are heartening because they show that asthmatics are engaging in the same levels of physical activity as nonasthmatics. This would seem to indicate that one of the goals of asthma management, that asthmatics should lead normal lives, has been achieved. But it is also disheartening to find that, like those in the general population without asthma, asthmatics are participating in too little physical activity. They are not meeting American guidelines for the levels of physical activity that have been shown to contribute toward the maintenance of good health. Physical activity has been shown to be protective for a variety of chronic illnesses such as hypertension, ischemic heart disease, type II diabetes mellitus, osteoporosis, colon cancer, anxiety, and depression. Low levels of activity are associated with increased mortality, and it has been estimated that 12% of deaths in the United States can be attributed to low levels of physical activity.2
One possible explanation for the findings in the study by Ford et al is that asthmatics try to be more active than the average person, but are unable to engage in sport because of their asthma; however, this would seem to be unlikely. Various studies have shown that asthmatics are able to exercise and improve their fitness, and that limitations in exercise capacity tend to relate more to lack of fitness rather than airflow obstruction. For example, army recruits with exercise-induced bronchoconstriction have been shown to be able to improve their peak oxygen uptake (
O2) to the same extent as those without bronchoconstriction after an intense physical training program.3
Aerobic training in mild asthma can increase fitness as measured by peak O2 and anaerobic threshold, as well as improving the ventilatory capacity, and reducing dyspnea associated with exertion.4
Asthmatics have been shown to have reduced peak O2, not because of ventilatory limitation from their asthma, but because of reduced fitness as indicated by the O2, O2, and anaerobic threshold.5
In asthmatics, their level of aerobic fitness has been found to correlate with their general level of activity rather than indexes of asthma severity such as expiratory flow rates or bronchial hyperreactivity. Despite this, their perception was that it was the asthma that limited their activity levels.6
A formal systematic review of the literature has shown that asthmatics are able to improve their cardiovascular fitness with exercise training, but without changes in lung function. There were no data found by this review to make conclusions about the effects of training on symptoms and quality of life. Thus asthmatics can be encouraged to be physically active, but the benefits will relate to improvements in physical fitness, and general health benefits, rather than in lung function specifically.7
A more likely explanation for the findings in the study by Ford et al is that the modern lifestyle, both at work and leisure, has led to more of the population becoming inactive, and asthmatics are not immune from this trend. If asthmatics are restricting their physical activity because of asthmatic symptoms, such as wheeze, breathlessness, cough or chest tightness, then it indicates that the asthma is not being well controlled. In such situations, steps should be taken to improve the management of the asthma, rather than let the patient continue to restrict his/her activities. Having asthma should not be a barrier to exercise.
Another finding of the study by Ford et al was that asthmatics are more likely to be obese than nonasthmatics. The study is not able to answer why this is so, but it is possible that some obese people have been mislabeled as asthma, because of exertional dyspnea and wheeze heard on examination. But the dyspnea could obviously be due to the extra weight that obese carry around, requiring extra work, and the wheeze could be due to earlier collapse of airways because of the obesity. Obesity has been shown previously to be a risk factor for self-reported asthma8 ; however, a recent study9 of > 16,000 adults showed that the most obese subjects were 1.5 times more likely to indicate that they had asthma, and were nearly twice as likely to use bronchodilators. They were 2.66 times more likely to experience dyspnea with exertion, but to have the lowest risk for airflow obstruction measured with spirometry. This suggests that asthma is overdiagnosed in obese people, and that there are other explanations for their dyspnea.9
We all have a responsibility to be involved in preventative medicine when dealing with individual patients, but also to use our influence in the wider community. One of the best ways to do this is to encourage everyone to be more physically active. The advice is simple, and that is that we should all undertake at least 30 min of moderate physical activity for all or most days of the week. (The "we" is deliberate here, because obviously, as physicians, we should be setting a good example and adopting this advice ourselves.) The activity does not have to be excessively vigorous. Examples of moderate activity for 30 min include walking for two miles, mowing the lawn pushing a motor mower, and playing tennis. The 30 min does not have to be continuous, but can be accumulated throughout the day with simple things such as using the stairs and walking for short trips instead of driving.2 Increasing the intensity as well as the duration of exercise can provide increased benefits, and it has been recently shown in 7,000 men, of whom 500 had cardiovascular disease, that those that engaged in strong or intense exercise had a reduction in ischemic heart disease by a third compared with those whose exercise was weak; there was a 14% reduction compared with those who engaged in exercise of a moderate intensity.10 Ford et al point out that not only are there general health benefits for asthmatics, but there is some evidence that the reduction in weight associated with increased physical activity, as well as the activity itself, may improve asthma control. In children, there has been shown to be a weak association between reduced fitness and the development of asthma.11 It is thus important for all of us working with asthmatics to look beyond the patients’ airways and offer advice about adopting adequate levels of physical activity
References
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