Chronic obstructive pulmonary disease (COPD) affects 15% (200,000) of the adult population of New Zealand. It is the fourth-most-common cause of death after cancer, heart disease, and stroke—and accounted for 5.1% of all deaths in 1999.1 This figure is likely to be an underestimate of the true mortality, as COPD is often a contributing factor to deaths recorded as due to other causes.

The disease is estimated to cost more than $13 million2 in hospital costs annually, and accounted for more than 9000 hospital discharges per year between 1997–1999. The total economic impact to the community is much greater, and includes healthcare costs incurred outside of hospital and intangible costs such as lost productivity from illness and premature death.

Smoking has long been recognised as the most important cause of COPD.3 Recently, however, there has been increasing interest in other factors which result in similar patterns of lung damage. Chronic asthma (especially if poorly controlled) can lead to changes in the lungs comparable to those caused by smoking.4 Asthmatics who smoke also have impaired response to treatment.5,6 This may lead to less satisfactory asthma control and an accelerated decline in lung function—an effect which is additional to that of the smoking itself.

Some workers are exposed to allergens (as well as vapours, gas, dust, and fumes) which may be significant in the development of COPD.7 In some countries, development of COPD has been shown to be independent of the effects of smoking, and it is estimated that one in five cases of COPD may be attributable to occupational exposure.8 However at-risk occupations tend to have high rates of smoking, and so the influence of combined factors is difficult to determine.

There have also been studies on the effects of air pollution on the development of chronic lung disease.9 For non-smokers, the most important form of air pollution is often exposure to environmental tobacco smoke, and this is an important factor in the development of many diseases, including COPD.10 Genetic factors such as alpha 1-antitrypsin deficiency are significant, and these effects are greatly accelerated if the person smokes.

Increasing understanding about these anatomical changes, which lead to COPD, has provided evidence which can support measures to modify the risk factors for the disease, including techniques to optimise management of asthma. This will reduce airway damage and remodelling, leading to chronic impairment of lung function. This evidence also provides strong support for effective industrial measures to reduce the effects of workplace hazards, and it adds to the evidence about the need to reduce air pollution. However New Zealand experiences lower levels of pollution compared to heavily industrialised countries and does not have many of the industries which lead to severe workplace exposures .

Therefore it must be emphasised that, in New Zealand, most cases of COPD result from chronic smoking. Recent estimates suggest that smoking accounts for 69% of the global burden of COPD.11 Low levels of air pollution and lack of heavy industry in New Zealand suggest that the contribution of smoking is likely to be higher. This effect is completely preventable, and provides many opportunities for intervention; smoking control remains the most effective measure to reduce the burden of COPD.

However many patients have a low awareness of the cause-and-effect link between smoking and COPD, and certainly a poor understanding of the magnitude of the risk. Perhaps there may be a well-intentioned attempt to shield patients from feelings of guilt and this can lead to a conspiracy of silence. Whilst poorly controlled asthma can certainly result in COPD, a more frequently encountered problem is the misdiagnosis of COPD as asthma.4 This leads to the inappropriate application of asthma treatments, and a failure to apply appropriate interventions; in particular, the failure to highlight the link between smoking and COPD and the need for smoking cessation.

Thousands of New Zealand smokers with COPD continue with their hazardous smoking behaviour without a true understanding of the risk. It is interesting to note that the same argument of protection of patients from guilt is rarely applied to lung cancer, where the link is widely acknowledged.

We are fortunate in New Zealand to have a wide range of smoking cessation support available throughout the country, and evaluations of these services show good success rates.12,13 Economic evaluations of smoking control interventions have demonstrated their cost-effectiveness and highlighted the value of investing in smoking cessation activities.

For example, a recent Ministry of Health study analysed the cost-effectiveness of subsidised Nicotine Replacement Therapy (NRT) made available through the Quitline service and through the Quit Cards programme, which provides subsidised NRT to primary healthcare providers.14

The study included an analysis comparing the estimated costs associated with these programmes and the health gains from long-term smoking cessation measured in Quality-adjusted Life Years (QALYs) with an estimate of NZ$2,942 per QALY.14,15 This compares favourably with cost per QALY estimates for a range of other health concerns such as NZ$3,478–$7,434 for green prescriptions, $25,000 for kidney transplantations, and $35–$50,000 for dialysis.14,15 Smoking cessation, which combines support with heavily subsidised NRT, is highly cost-effective.

We need to be vigilant in correctly diagnosing COPD. Most of these patients will have developed the disease after a long period of smoking. Medical practitioners need to be aware of the diagnostic problems especially in relation to asthma. Smoking cessation is the only effective measure which will alter the natural history of this disease, and medical practitioners have a major role in initiating the process of assisting a smoker to quit.

The combination of simple advice and heavily subsidised NRT is very cost-effective and needs to be easily available.

Author information: Peter Martin, Medical Advisor; Helen Glasgow, Director, The Quit Group; Jane Patterson, Director, Asthma and Respiratory Foundation of New Zealand, Wellington

Correspondence: Peter Martin, Medical Advisor, The Quit Group; PO Box 12 605, Wellington. Fax: (04) 470 7632; email: peter.martin@quit.org.nz