Use of histamine-2 receptor antagonists (H2RAs) and risk of community-acquired pneumonia (CAP)
| Exposure | CAP events n | Incidence rate per 1000 person-years | Age/sex-adjusted HR (95% CI) | Fully adjusted HR# (95% CI) |
| Never PPI or H2RA | 21 471 | 19.1 | Reference | Reference |
| H2RA use by time since last prescription | ||||
| Current: 1–30 days | 780 | 85.4 | 2.28 (2.12–2.45) | 1.80 (1.67–1.94) |
| Recent: 31–60 days | 491 | 77.3 | 2.04 (1.87–2.23) | 1.68 (1.53–1.85) |
| Past: 61–210 days | 1479 | 66.6 | 1.95 (1.85–2.06) | 1.65 (1.55–1.74) |
| Distant past: ≥211 days | 3943 | 26.4 | 1.24 (1.20–1.29) | 1.19 (1.15–1.23) |
| Current H2RA use by duration of use | ||||
| 1–30 days | 330 | 68.2 | 2.04 (1.83–2.27) | 1.90 (1.71–2.12) |
| 31–60 days | 77 | 87.6 | 1.95 (1.56–2.44) | 1.83 (1.46–2.29) |
| 61–210 days | 237 | 110.8 | 2.45 (2.15–2.78) | 2.27 (1.99–2.58) |
| ≥211 days | 136 | 106.4 | 3.09 (2.61–3.66) | 2.63 (2.22–3.11) |
| Current use of both PPI and H2RA | 73 | 111.1 | 3.47 (2.76–4.36) | 2.52 (2.00–3.18) |
PPI: proton pump inhibitor; HR: hazard ratio. #: adjusted for age, sex, history of pneumonia, gastro-oesophageal reflux 1 year before, asthma, bronchopulmonary dysplasia and cystic fibrosis. All analyses are adjusted for use of PPIs.