Effect of inhaled corticosteroids on systemic inflammation in asthma

BACKGROUND: Recent research using serum high sensitivity C-reactive protein (hs-CRP) has evidenced existence of low grade systemic inflammation in asthmatics whose correlation with various clinical indices is not fully studied. OBJECTIVE: To investigate the relationship between systemic inflammation and various clinical and treatment characteristics of asthma. MATERIALS AND METHODS: Forty asthmatics (22 steroid inhaling and 18 steroid naïve) and 40 healthy subjects matched for age and sex were examined cross-sectionally. Along with clinical assessment, serum hs-CRP levels were measured for all subjects using latex enhanced immunoturbidometry method. RESULTS: Serum hs CRP levels were significantly higher in steroid naïve asthmatics when compared to normal subjects (0.93 ± 1.18 vs 0.24 ± 0.31 mg/dL, respectively; Mann-Whitney U test, P < 0.001). This association persisted after adjusting for age, gender, body mass index (BMI), and socioeconomic status (adjusted odds ratio 10.47; 95% CI 1.88-58.3; P < 0.01). Steroid inhaling asthmatics had serum hs-CRP levels comparable with control group (0.17 ± 0.18 vs 0.24 ± 0.31 mg/dL respectively, P > 0.05). Among the clinical and treatment related variables, duration of inhaled steroids usage alone correlated significantly with serum hs-CRP levels (Pearson correlation coefficient r = 0.449, P < 0.05), which was independent of age, BMI, duration of illness, and frequency of emergency visits. CONCLUSION: This study confirms the existence of low grade systemic inflammation in asthma which is effectively controlled by inhaled steroids. Such an effect of inhaled steroids appears to be more pronounced in recent users than that of long-term users, possibly due to lower adherence rate among the latter.