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To investigate the effect of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers on pneumonia hospitalization in patients with stroke history in Taiwan.We conducted a case-crossover study using the National Health Insurance Research Database in Taiwan during the period from 1998 to 2007. Patients who had stroke history and were subsequently admitted for pneumonia were enrolled for analysis. The status of exposure to angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers 1–30 days prior to admission (case period) was compared to that during 91–120 days and 181–210 days before admission (control periods) for each patient. Conditional logistic regression was used to estimate the odds ratio (OR) and 95% confidence interval (95% CI) for the association between pneumonia and use of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers.In this study, 13 832 patients with incident pneumonia from the stroke patient population were enrolled. After adjustment for time-varying confounding factors, angiotensin-converting enzyme inhibitor use was associated with a decreased pneumonia risk (OR 0.70; 95% CI 0.68–0.87) and a significant dose–response relationship (P < 0.01). The pneumonia risk associated with angiotensin II receptor blockers use was not significant (OR 1.02; 95% CI 0.87–1.19).Our study revealed a significant protective effect with dose–response relationship of angiotensin-converting enzyme inhibitor use on hospitalization for pneumonia among stroke patients. Further studies to confirm the protective effect of angiotensin-converting enzyme inhibitor use on pneumonia risk are warranted.