The association of renin–angiotensin system blockades and pneumonia requiring admission in patients with COPD

BACKGROUND: The hallmark of COPD is chronic airway inflammation, which may be mediated by renin–angiotensin system. The renin–angiotensin system blockers such as angiotensin-converting enzyme inhibitors (ACEi) and angiotensin II receptor blockers (ARBs) have exhibited anti-inflammatory and immunomodulatory effects in patients with various diseases. We explored the effects of ACEi and ARBs on the risk of pneumonia in patients with COPD. METHODS: A nested case–control study was performed on COPD patients recruited from January 2010 to August 2013 in two referral hospitals in Korea. A total of 130 COPD patients admitted with pneumonia were included, and 245 COPD patients without pneumonia were selected as controls from a total of 1,646 such patients. Controls were matched with test patients by age, sex, and severity of airflow limitation. The effects of ACEi/ARBs use on the odds ratio (OR) for the development of pneumonia were tested through conditional logistic regression. RESULTS: Elderly patients (over 70 years of age) constituted ~30% of each group; most of the patients were male (85%). Of the COPD patients with pneumonia, 21.5% had taken ACEi/ARBs for a mean of 9.8 months (standard deviation ±3.5 months). The proportions of ACEi/ARBs users and the mean duration of such use did not differ when compared to those of the control patients (26.9%, P=0.25; 9.6±3.6 months, P=0.83). Univariate analyses indicated that the use of ACEi/ARBs was not associated with a decreased risk of pneumonia (OR =0.70, 95% confidence interval 0.41–1.23, P=0.21), whereas both a history of pulmonary tuberculosis (OR =1.85, 95% confidence interval 1.12–3.06, P=0.02) and exposure to systemic steroids (OR =2.33, 95% confidence interval 1.28–4.23, P=0.005) did show an association. After adjustment for a history of tuberculosis, comorbid chronic renal disease, and exposure to corticosteroids, ACEi/ARBs reduced the risk of pneumonia in COPD patients (OR =0.51, 95% confidence interval 0.27–0.98, P=0.04). CONCLUSION: This study revealed that the use of ACEi/ARBs was associated with reducing the risk of pneumonia in patients with COPD. Further prospective studies are necessary to confirm the protective effect of ACEi/ARBs and elucidate the underlying mechanisms in COPD patients.