Moving house: a risk factor for the development of childhood asthma?BMJ 1995; 311 doi: https://doi.org/10.1136/bmj.311.7012.1069 (Published 21 October 1995) Cite this as: BMJ 1995;311:1069
- aHealth Centre, Estover, Plymouth PL6 8UE
- bDepartment of Child Health, Derriford Hospital, Plymouth PL6 8DH
- Correspondence to: Dr Hughes
- Accepted 7 July 1995
Following the observation that asthma was commonly seen in children who had previously moved house we undertook a case control study to investigate the timing of house moves, taking account of other factors known to be associated with childhood asthma. A Medline search failed to identify any studies reporting house moves as a risk factor for childhood asthma.
Subjects, methods, and results
We carried out the study in a single, computerised practice serving a suburban population with modern housing. All children between their 4th and 16th birthdays receiving treatment for asthma in the year to February 1994 were identified from computerised prescription records.
The study subjects were 44 children treated for asthma. One control child without atopy, matched for sex and age, was randomly selected from the practice register for each asthmatic subject. A telephone survey using a structured questionnaire was undertaken and combined with information obtained from the child's and parents' practice records. The two groups were compared for house moves using McNemar's test for matched cases and controls, with adjustment for small numbers. Other differences were assessed using the χ2 test.
The characteristics of the two groups are shown in the table. The 44 asthmatic children constituted 11.4% of the 4-16 year olds in the practice.
Twenty five (57%) asthmatic children had moved house by the age of onset of asthma, in contrast to 4 (9%) of matched control children at the same age (P<0.0001, McNemar's test; odds ratio 13.2, 95% confidence interval 4.0 to 43.2). There was no significant difference in the rate of house moves between the groups after the age of onset in the asthmatic child. There was no significant difference between the asthmatic and control children for rates of parental atopy, smoking, or separation; methods of heating (mostly gas central heating); the presence of pets kept indoors; breast feeding; prematurity; or birth order.
This study shows a strong association between house moves in families with young children to previously inhabited, centrally heated dwellings and the subsequent development of childhood asthma. Social class differences were unlikely to have explained such a strong association, and no family moved on medical grounds. Parental recall about the timing of previous house moves appeared excellent. Parents were blind to the purpose of the study, and recall bias should have been similar between the two groups. The difference in rate of house moves was confined to those occurring before the onset of asthma.
In one recent prospective cohort study,1 house moves were not reported as a factor. Total house moves from birth were significantly associated with asthma in the 1958 British Births cohort.2 One study on the 1970 cohort reported an association between house moves and lower respiratory illness in the first five years.3 In another study the time at the present address was not associated with absence from school because of asthma.4
The reasons for the association are unclear: moving at a young age will expose children to new allergens, particularly in a modern house with central heating and limited ventilation, and is likely to be stressful. As most house moves were local, a change in the level of air pollution would not explain the findings.
The non-significant trend towards being the firstborn in the asthmatic group was in accordance with the previously recognised association.5 This may be explained by the effect of house moves.
The findings of the present study need to be confirmed in other populations before a definite association is established. If so, this would have major implications for public health measures aimed at reducing the prevalence of childhood asthma.
We thank P A Parritt, practice nurse, and P J Young, health visitor, who assisted in administering the questionnaires.
Conflict of interest None.