Relationship between socioeconomic status and asthma: a longitudinal cohort study
- R J Hancox1,
- B J Milne1,
- D R Taylor2,
- J M Greene3,
- J O Cowan2,
- E M Flannery2,
- G P Herbison4,
- C R McLachlan2,
- R Poulton1,
- M R Sears3
- 1Dunedin Multidisciplinary Health and Development Research Unit, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
- 2Department of Medical and Surgical Sciences, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
- 3Firestone Institute for Respiratory Health, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
- 4Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
- Correspondence to:
Dr R J Hancox
Dunedin Multidisciplinary Health and Development Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, PO Box 913, Dunedin, New Zealand;
- Received 20 May 2003
- Accepted 23 December 2003
Background: There is conflicting information about the relationship between asthma and socioeconomic status, with different studies reporting no, positive, or inverse associations. Most of these studies have been cross sectional in design and have relied on subjective markers of asthma such as symptoms of wheeze. Many have been unable to control adequately for potential confounding factors.
Methods: We report a prospective cohort study of approximately 1000 individuals born in Dunedin, New Zealand in 1972–3. This sample has been assessed regularly throughout childhood and into adulthood, with detailed information collected on asthma symptoms, lung function, airway responsiveness, and atopy. The prevalence of these in relation to measures of socioeconomic status were analysed with and without controls for potential confounding influences including parental history of asthma, smoking, breast feeding, and birth order using cross sectional time series models.
Results: No consistent association was found between childhood or adult socioeconomic status and asthma prevalence, lung function, or airway responsiveness at any age. Having asthma made no difference to educational attainment or socioeconomic status by age 26. There were trends to increased atopy in children from higher socioeconomic status families consistent with previous reports.
Conclusions: Socioeconomic status in childhood had no significant impact on the prevalence of asthma in this New Zealand born cohort. Generalisation of these results to other societies should be done with caution, but our results suggest that the previously reported associations may be due to confounding.
The Dunedin Multidisciplinary Health and Development Research Unit is funded by the Health Research Council of New Zealand. The respiratory section of the study was funded by the Health Research Council, the Otago Medical Research Foundation, the New Zealand Lottery Grants Board, and the Asthma Foundation of New Zealand.