A Cochrane review [Abstract] 1 on workplace interventions for the treatment of occupational asthma included 21 studies with a total of 1 447 subjects. All studies were observational in nature. Removal from exposure increased the likelihood of reporting absence of symptoms (RR 21.42, 95% CI 7.20 to 63.77), improved forced expiratory volume (FEV1 %; MD 5.52 percentage points, 95% CI 2.99 to 8.06) and decreased non-specific bronchial hyper-reactivity (SMD 0.67, 95% CI 0.13 to 1.21) when compared with continued exposure (15 studies).Reduction of exposure increased the likelihood of reporting absence of symptoms (RR 5.35, 95% CI 1.40 to 20.48) but did not affect FEV1 % (MD 1.18 percentage points, 95% CI -2.96 to 5.32) when compared with continued exposure (6 studies).Removal from exposure increased the likelihood of reporting absence of symptoms (RR 39.16, 95% CI 7.21 to 212.83) but did not affect FEV1 % (MD 1.16 percentage points, 95% CI -7.51 to 9.84) when compared with reduction of exposure (8 studies).Two studies reported that the risk of unemployment after removal from exposure was increased compared with reduction of exposure (RR 14.3, 95% CI 2.06 to 99.16). Three studies reported loss of income of about 25% after removal from exposure.
Removal from exposure is associated with an increased risk of unemployment, whereas reduction of exposure is not. The clinical benefit of removal from exposure or exposure reduction should be balanced against the increased risk of unemployment.
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