Asthma in Australia 2008Header
Table of Contents | Chapter 1  2  3  4  5  6  7  8  | Appendix 1 2 | References |

7. Tobacco smoke and occupation as risk factors for asthma

| Introduction | 7.1 People with asthma who smoke | 7.2 Passive smoke exposure in children with asthma | 7.3 Occupational asthma |

7.2 Passive smoke exposure in children with asthma
| Introduction | 7.2.1 Exposure to passive smoke inside the home |

Introduction                     [back to top]

Exposure to environmental tobacco smoke, commonly referred to as ‘passive smoke’, in childhood is a risk factor for the development of asthma symptoms and also for the worsening of pre-existing asthma. It has been shown that exposure to environmental tobacco smoke increases the risk of wheezing illness in young children (Martinez et al. 1992; Young et al. 2000) and that the association between exposure and childhood wheezing illness is most consistent at high levels of environmental tobacco smoke exposure (NHMRC 1997). These findings are supported by evidence from international studies which conclude that parental smoking is associated with more severe asthma in children (Pattenden et al. 2006; Strachan & Cook 1998) and that exposure to environmental tobacco smoke after birth is a likely cause of wheezing or other acute respiratory illness in young children (Strachan & Cook 1997).

Cohort studies have shown that children with pre-existing asthma who are exposed to environmental tobacco smoke have increased morbidity and asthma symptoms ( href="References.htm#Murray1989">Murray & Morrison 1989), more frequent exacerbations (Chilmonczyk et al. 1993), more severe asthma symptoms (Murray & Morrison 1993; Strachan & Cook 1998), impaired lung function (Chilmonczyk et al. 1993; Murray & Morrison 1989) and increased airway reactivity (Murray & Morrison 1989; Oddoze et al. 1999) or peak flow variability (Fielder et al. 1999; Frischer et al. 1993). There is also evidence that children exposed to environmental tobacco smoke are more likely to attend emergency departments with asthma (Evans et al. 1987). It has been shown that prevention of indoor smoking leads to a reduction in hospital admissions in children with asthma (Gurkan et al. 2000). Recovery after hospitalisation, measured by use of reliever medication and number of symptomatic days, is also impaired in children exposed to passive smoke (Abulhosn et al. 1997).

A Brisbane study conducted between 1981 and 1998 showed that 14-year-old girls, but not boys, had an increased risk of having asthma symptoms (odds ratio 1.96; 95% CI 1.25–3.08) if their mother reported smoking heavily (defined as 20 or more cigarettes per day) both during pregnancy and 6 months after the birth of their daughter (Alati et al. 2006). Smoking during pregnancy was the most important risk factor.

There is some evidence that early life exposure to tobacco smoke may have long-term consequences. A recent study has reported that as much as 17% of adult-onset asthma is attributable to maternal smoking in childhood (Skorge et al. 2005). Several other international studies have reported associations with passive smoke exposure in childhood and asthma in adulthood. A Swedish study showed that the prevalence of adult asthma among people who never smoked was higher among subjects who had been exposed to environmental tobacco smoke as a child (Larsson et al. 2001). Findings from the European Community Respiratory Health Survey showed a higher prevalence of respiratory symptoms and poorer lung function among adults whose mother smoked during pregnancy or had childhood exposure to maternal smoking (Svanes et al. 2004).

Other studies have reported that subjects who were exposed to passive smoke during their childhood are more likely to take up smoking themselves (Cook & Strachan 1999; Larsson et al. 2001) and this may increase their risk of developing asthma.

The large body of evidence regarding the harmful consequences of passive smoke exposure has resulted in the introduction of smoking bans in many public areas. Recent legislative changes in Australia prohibit smoking in places such as bars, cafes and restaurants, shopping centres, entertainment venues and the workplace. South Australia recently became the first state to ban smoking in cars carrying children under the age of 16 years. In New South Wales in 2006, 88% of adults reported that their car was smoke-free (Centre for Epidemiology and Research 2007). Unfortunately, young children, who are most vulnerable to the effects of passive smoke exposure, are most likely to be exposed to passive smoke in their home, where smoking bans do not apply. There is evidence, though, that the proportion of homes in which smoking was not permitted inside the house increased in Australia from 71.6% in 1999 to 80.1% in 2004 (Valenti et al. 2005).

This section provides data on the proportion of children with asthma who live in homes where smoking occurs inside the home.

7.2.1 Exposure to passive smoke inside the home                     [back to top]

Australian children with asthma continue to be exposed to environmental tobacco smoke in the home despite the known adverse effects. In 2004–05, 39.1% of children aged 0–14 years with asthma lived with one or more cigarette smokers. This proportion was marginally higher than that observed among children without asthma (36.2%). Furthermore, 11.0% of children with asthma were residing in homes where smoking occurred inside the home (Table 7.2). This rate was significantly higher than that observed for children without asthma (9.4%; p = 0.04). Results from health surveys conducted in Victoria, Western Australia and South Australia support these findings (Table 7.2).

Table 7.2: Exposure to passive smoke among children, 2004–2007

High rates of exposure to environmental tobacco smoke were observed for children of all ages with and without asthma (Figure 7.3).

Figure 7.3: Proportion of children aged 0–14 years residing with one or more cigarette smokers who usually smoke inside the house, by age group and current asthma status, 2004–05

Socioeconomic disadvantage

In the most socioeconomically disadvantaged localities, nearly two-thirds of children with current asthma reside with a smoker. This proportion declines to 14% in the least socioeconomically disadvantaged localities (Figure 7.4).

Figure 7.4: Proportion of children aged 0–14 years with one or more cigarette smokers in the household, by socioeconomic status and current asthma status, 2004–05

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