Summary of studies of asthma severity
| Reference | Age | Index of severity | Index of exposure | Association of disease severity with passive smoke exposure: | |||||
|---|---|---|---|---|---|---|---|---|---|
| Direction | p value | Comments | |||||||
| Population-based case series: | |||||||||
| 35 | 12–18 | Frequency and intensity | Mother smoking | Positive | 0.02 | Mother smoked in 34% (38/113) children with both frequent and intense attacks and 23% (84/373) of less severe cases | |||
| 36 | 7–12 | Attack frequency | Household smoking | Inverse | 0.59 | 35% (29/82) infrequent wheezers and 30% (20/67) with ⩾5 attacks per year were exposed to ETS. Urinary cotinine levels similar in the two groups | |||
| 37 | 7–9 | Frequency and intensity | Mother smoking | Weak +ve | ? | Published odds ratio 2.04 (1.25 to 3.34) for severe wheeze (179 cases) is similar to 1.87 (1.25 to 2.81) for all wheeze (325 cases) | |||
| 46 | 0–17 | Functional impairment | Mother smoking | Positive | 0.47 | Functional impairment reported for 22% of asthmatics whose mothers smoked (n=144) and 18% of the remaining asthmatics (n=128) | |||
| 49 | 2–5 | Asthma medication | Mother smoking | Positive | 0.08 | Medication taken by 41% of asthmatics whose mother smoked ⩾10/day (n=23) and 19% of other asthmatics (n=76) | |||
| 50 | 0–5 | Hospitalisations | Mother smoking | No trend | 0.88 | Mean admission rates 1.1 per year if mother non-smoker, 1.3 if mother smoked <10/day, and 1.0 per year if mother smoked ⩾10/day | |||
| Clinic-based case series: | |||||||||
| 45 | 1–13 | Composite score | Household smoking | Positive | 0.15 | Exposure (mainly to non-maternal smoking) in 23% (43/186) mild, 26% (23/87) moderate and 31% (33/107) severe cases | |||
| 47 | 4–17 | ER visits per year | Any ETS exposure | Positive | 0.008 | Mean 3.1 visits per year in 137 smoking homes, 1.8 per year in 122 non-smoking homes | |||
| 48 | 1–17 | Composite score | Mother smoking | Positive | <0.01 | Severity score related to maternal smoking (p<0.01) but not to paternal smoking (p>0.5) | |||
| 51 | 1–17 | Composite score | Mother smoking | Inverse | <0.01 | Reversal of previous relationship[45] after introduction of anti-smoking advice (see text) | |||
| 52 | 0–13 | Attack frequency | Urinary cotinine | Positive | <0.05 | Mean 3.6 episodes per year if cotinine >39 ng/ml (n = 30), 2.8 per year if 10–39 ng/ml (n = 53), 2.1 per year if <10 ng/ml (n = 116) | |||
| 53 | 5–12 | Intubation | Any ETS exposure | Positive | <0.001 | 85% (11/13) intubated patients and 20% of 287 non-intubated admissions were exposed to ETS (odds ratio 22.4, 95% CI 7.4 to 68.0) | |||
| 54 | 1–10 | Readmission | Household smoking | Positive | 0.24 | 53% (17/32) patients readmitted and 36% (13/36) children not readmitted were from smoking homes (odds ratio 2.01, 95% CI 0.76 to 5.30) | |||
ETS = environmental tobacco smoke.