Passive smoking may link asthma and social deprivation

Exposure to environmental tobacco smoke may be a major cause of asthma attacks among disadvantaged children. The findings of a large cross sectional study may explain the recognised association of prevalence and severity of asthma with low income and deprivation and indicate a potential control measure.

Among 2986 Canadian schoolchildren with asthma studied, asthma attacks requiring an emergency hospital visit or overnight stay were significantly linked with family income. The mean frequency of hospital visits per year was 25% versus 16% for children of families with a yearly income of <$20 000 or >$60 000, respectively. Other significant factors were young age (5–12 years), lower parental education, unmarried parents, regular exposure to environmental tobacco smoke, and indicators of poor asthma control.

When compared across three bands of family income (<$20 000, $20 0000–$60 000, and >$60 000) each factor was associated with lower income. Multiple logistic regression showed that low income remained associated with hospital visits after adjusting for age, sex, and level of current asthma treatment but not after adjusting for parental education or exposure to environmental tobacco smoke.

The children were drawn from participants in a questionnaire survey of Canadian schoolchildren with asthma (Student Lung Heath Survey) who were aged 5–19 years with asthma previously diagnosed by a doctor. They or their parents provided information about family income (total household income before tax in the previous 12 months), hospital visits due to asthma (to the emergency department or entailing an overnight stay or longer in the same period) , and other potential risk factors for asthma.