Demographic, respiratory health, and occupational characteristics of the study population
| Cases | Controls | |
|---|---|---|
| Number (%) or median (minimum to maximum) are given. | ||
| *Asthma attack and/or nocturnal attack of shortness of breath in the last year. | ||
| †Regular cough and/or regularly bringing up phlegm. | ||
| ‡n = 35 cases and 126 controls. | ||
| §FEV1 <80% of predicted and FEV1 to FVC ratio <70%. | ||
| ¶Specific serum IgE to at least one of nine common allergens. | ||
| **n = 37 cases and 126 controls. | ||
| ††Assessed by using a job exposure matrix with additional expert judgement.9 | ||
| ‡‡Fall of at least 20% in FEV1 associated with a methacholine dose of ⩽1 mg; n = 22 cases and 95 controls. | ||
| Total number | 40 (100%) | 155 (100%) |
| Age (years) | 48 (31 to 64) | 51 (33 to 65) |
| Current smokers | 11 (28%) | 15 (10%) |
| Ex-smokers | 4 (10%) | 10 (7%) |
| Asthma symptoms* | 24 (60%) | 0 (–) |
| Chronic bronchitis symptoms† | 26 (65%) | 0 (–) |
| FEV1 (% of predicted)‡ | 99 (68 to 127) | 99 (72 to 125) |
| COPD§, ‡ | 2 (6%) | 1 (1%) |
| Bronchial hyperresponsiveness‡‡ | 4 (18%) | 3 (3%) |
| Atopy¶** | 6 (16%) | 19 (15%) |
| Total serum IgE >100 kU/l** | 10 (27%) | 8 (6%) |
| Current working hours per week in domestic cleaning | 18 (3 to 50) | 16 (3 to 80) |
| Years of employment in domestic cleaning | 16 (2 to 53) | 17 (1 to 53) |
| Ever employed in a non-domestic cleaning job | 31 (78%) | 54 (35%) |
| Ever employed in a non-cleaning job with asthma related exposures†† | 11 (28%) | 55 (35%) |
| Ever inhaled an important quantity of vapours, gas, or fumes related to cleaning agents | 31 (78%) | 79 (51%) |