Cigarette smoking impairs the therapeutic response to oral corticosteroids in chronic asthma

The study was designed to assess the effect of cigarette smoking on the therapeutic response to oral corticosteroids in chronic stable asthma. We performed a randomized, placebo-controlled, crossover study with prednisolone (40 mg daily) or placebo for 2 weeks in smokers with asthma, ex-smokers with asthma, and never-smokers with asthma. All subjects had reversibility in FEV1 after nebulized albuterol of 15% or more and a mean postbronchodilator FEV1% predicted of more than 80%. Efficacy was assessed using FEV1, daily PEF, and an asthma control score. There was a significant improvement after oral prednisolone compared with placebo in FEV1, ml (mean difference, 237; 95% confidence intervals, 43, 231; p = 0.019), morning PEF L/m (mean difference, 36.8; 95% confidence intervals (CI), 11, 62; p = 0.006), and asthma control score (mean difference, -0.72; 95% CI, -1.2, -0.3; p = 0.004) in never-smokers with asthma but no change in smokers with asthma (mean differences of 47, 6.5, and -0.05 with p values of 0.605, 0.47, and 0.865, respectively). Ex-smokers with asthma had a significant improvement in morning and night PEF (mean difference, 29.1; CI, 2.3, 56; p = 0.04 and 52.4; CI, 26, 79; p = 0.003, respectively), but not in FEV1 or asthma control score. We conclude that active smoking impairs the efficacy of short-term oral corticosteroid treatment in chronic asthma.