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Title: An epidemiological study of respiratory disease and the home environment in seven-year-old children
Author: Strachan, David Peter
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1990
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A cross-sectional study of seven-year-old children was conducted to explore the relationship between damp, mouldy housing and childhood asthma, and the effects of passive tobacco smoke exposure upon respiratory symptoms, lung function and middle ear effusion. A random cluster sample of 1095 school children were contacted. Following a postal questionnaire to parents, 892 children were examined. Baseline spirometry, exercise-induced brochospasm (EIB), and impedance tympanograms were measured. Salivary cotinine concentration was determined for 770 children. Bedroom temperature and relative humidity were monitored continuously for 7 days in the homes of 317 children. The repeatability of each of the measurements was assessed. Among 1000 children with questionnaire data, 123 (12.3%) were reported to have wheezed in the previous year. Recent wheeze was strongly associated with report of mould in the home (odds ratio 3.70, 95&37 CI 2.22-6.15, X2 27.7, 1df), and this association was substantially independent of other aspects of the home environment. However, reported dampness and mould growth were only weakly associated with EIB and impaired baseline spirometry. Differences in adjusted weekly mean temperature and relative humidity between the bedrooms of wheezy and non-wheezy children were small and non-significant, although in the expected direction (-0.4 degC, t -1.3, 315df; +1.1% RH, t +1.1, 315df). Tympanometric findings were unrelated to bedroom conditions. At every level of measured EIB, recent wheeze was reported more commonly for children from mouldy homes, and the association between mould and wheeze was substantially independent of EIB. These findings confirm those of a preliminary study and suggest that the association between damp or mouldy housing and childhood asthma may be principally due to greater awareness of respiratory symptoms by parents who consider their home to be mouldy. Further studies of this association will benefit from objective measurements of both exposure and disease. Cotinine was detected in the saliva of 85% (658/770) children. Six children had levels greater than 15 ng/ml, which may indicate experimentation with active smoking. Cotinine concentrations were strongly related to the number of smokers in the household, female sex and rented housing. Most respiratory symptoms, including wheeze, were not associated with salivary cotinine. All spirometric indices except FVC were inversely correlated with cotinine level, the effect being greatest for end-expiratory flow rates. Adjusting for sex, height, test conditions and housing tenure, differences in FEF75-85% and FEF75% between the top and bottom quintiles of salivary cotinine were each about 7%, equivalent to a reduction of 1.1% (95% CI 0.1% -2.1%) per doubling of cotinine concentration. Further cross-sectional studies of passive smoking in childhood should include measures of end-expiratory airflow. The long-term significance of these spirometric changes can only be assessed by longitudinal studies, preferably using biochemical markers of tobacco smoke exposure in subjects who have never actively smoked. Tympanograms indicating middle ear effusion (Type B) were found in 9.4% (82/872) children. The housing characteristic most strongly related to effusion was the number of smokers in the household, the odds ratio for two or more smokers (compared to none) being 1.9 (95% CI 1.1-3.4, X2 4.1, 1df). Tympanometric abnormalities were strongly related to salivary cotinine level, the odds ratio for effusion being 1.14 per doubling of the cotinine concentration (95% CI 1.03-1.27, X2 6.6, 1df). Adjustment for sex, housing tenure and a range of specific housing variables made little difference to this result. At least one-third of middle ear effusions in this population were statistically attributable to passive smoke exposure. These findings are consistent with three case-control studies and one population survey of this age-group, and suggest that middle ear effusion should be added to the list of hazards attributable to passive smoking.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available