Asthma in cleaners: a distinct phenotype?

Background: Cleaners have an increased risk of work-related asthma, but few epidemiological studies have used objective tests. Aims: To examine the characteristics and determinants of respiratory symptoms and lung function deficits in New Zealand cleaners. Methods: Symptoms, lung function, atopy, and cleaning exposures were assessed in 425 cleaners and reference group of 281 retail workers/bus drivers using a standardised questionnaire, spirometry, and skin prick testing. Results: Cleaners had an increased risk of current asthma, defined as: woken by shortness of breath, asthma attack, or current asthma medication (aOR=1.83, 95%CI 1.18-2.85). Despite this, they had similar rates of current wheeze (aOR=0.92, 95%CI 0.65-1.32) in the last year and were less likely to have a doctors diagnosis of asthma (aOR=0.62, 95%CI 0.42-0.92). Cleaners overall had lower lung function (FEV₁, FVC, PEF, FEF_25-75; p<0.05). Asthma in cleaners was associated with less atopy (aOR=0.35, 95%CI 0.13-0.90), fewer wheezing attacks (aOR=0.40, 95%CI 0.17-0.97; for over 3 times per year vs. 3 times or less) and reduced bronchodilator response (6% versus 9% mean FEV₁ % predicted change, p<0.05) compared to asthma in reference workers. Cleaning of cafes/restaurants/kitchens and using upholstery sprays was associated with more symptoms, whilst several specific exposures were also associated with lung function deficits (p<0.05). Conclusions: Cleaners have an increased risk of some asthma-associated respiratory symptoms and reduced lung function. However, asthma in cleaners was not associated with wheeze and atopy, and airway obstruction was less reversible. Asthma in cleaners may therefore represent a distinct phenotype.