7. Tobacco smoke and occupation as risk factors for asthma
Introduction [back to top]
The harmful effects of both active and passive smoking are well known. People with asthma who smoke have particular problems (Siroux et al. 2000) and find their asthma more difficult to control than non-smokers. In part, this may be because smoking impairs the effectiveness of inhaled corticosteroids (Chalmers et al. 2002), even at high doses (Pedersen et al. 1996). In addition, both smoking and asthma accelerate the rate of decline in lung function with age (James et al. 2005).
7.1.1 Prevalence [back to top]
In 2004–05, the prevalence of smoking at least once a week in people aged 18 years and over was 24.5% among those with current asthma and 22.3% among those without current asthma (Table 7.1). Survey data from the states and territories confirm that the rate of smoking among people with asthma (15.8–35.5%) is the same, if not higher than, the rate among people without asthma (Table 7.1). The proportion of ex-smokers is generally similar among those with and without asthma.
A South Australian study incorporating over 10 years of aggregated omnibus data found that asthma was associated with ex-smoking status. The prevalence of asthma among ex-smokers was 1.29 times (95% CI 1.15–1.44) as high as the prevalence of asthma among non-smokers (Wilson et al. 2006). Furthermore, the prevalence of asthma among female smokers was 1.27 times (95% CI 1.08–1.51) as high as the prevalence among non-smokers. Similarly, among males, the prevalence of asthma among ex-smokers was 1.47 times (95% CI 1.20–1.80) as high as the prevalence among non-smokers.
It is clear that many people with asthma continue to smoke. However, it is also possible that the very high rates of smoking (and particularly ex-smoking status) reflect the causal pathway. In other words, some people may have asthma-like symptoms or have been diagnosed with asthma due to the adverse effects of smoking.
7.1.2 Population subgroups [back to top]
Age and sex
The prevalence of current smoking in adults decreases with age but, among men, the prevalence of ever having smoked increases with age. As a consequence, and as expected, a far higher proportion of older people, particularly men, are ex-smokers (ACAM 2007a). In 2004–05, nearly 38% of young men aged 18–34 years with asthma continued to smoke despite their illness (Figure 7.1).
The relatively high, or at least similar, rates of smoking in people with asthma compared to people without asthma is observed in both males and females (Figure 7.1). Among adult females, 23.5% of those with asthma compared to 19.2% of those without asthma reported being current smokers. Among adult males, 26.1% of those with asthma were smokers compared to 25.2% of those without the condition.
The prevalence of smoking among people with asthma in 2004–05 was over three times higher (40.0%) among those living in more socioeconomically disadvantaged areas than among those living in less disadvantaged localities (12.4%) (rate ratio 3.2; 95% CI 2.4–4.2) (Figure 7.2). This differential was less marked among people without asthma (rate ratio 2.0; 95% CI 1.8–2.2).
Among those living in the most disadvantaged localities, the prevalence of smoking among people with asthma (40.0%) was substantially higher than that observed among people without the condition (31.0%). However, there were no statistically significant differences in the prevalence of smoking among people with and without asthma living in the least disadvantaged areas.
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