Characteristics of patients with and without rheumatoid arthritis (RA) who were hospitalised for pneumonia from 1997 to 2011 in northern Denmark
| RA | Non-RA | |
| N | 1220 (2.3%) | 51 357 (97.7%) |
| Pneumonia 1997–2001 | 277 (1.8%) | 15 011 (98.2%) |
| Pneumonia 2002–2006 | 411 (2.3%) | 17 657 (97.7%) |
| Pneumonia 2007–2011 | 532 (2.8%) | 18 674 (97.2%) |
| Age, median | 74 (66–80) | 72 (59–81) |
| 16–39 years | 18 (1.5%) | 4406 (8.6%) |
| 40–49 years | 35 (2.9%) | 3311 (6.5%) |
| 50–59 years | 120 (9.8%) | 5739 (11.2%) |
| 60–69 years | 249 (20.4%) | 8890 (17.3%) |
| 70–79 years | 454 (37.2%) | 13 176 (25.7%) |
| 80–89 years | 306 (25.1%) | 12 699 (24.7%) |
| 90–105 years | 38 (3.1%) | 3136 (6.1%) |
| Sex | ||
| Women | 801 (65.7%) | 24 018 (46.8%) |
| Men | 419 (34.3%) | 27 339 (53.2%) |
| Comorbidity | ||
| Congestive heart failure | 170 (13.9%) | 5269 (10.3%) |
| Peripheral vascular disease | 118 (9.7%) | 3811 (7.4%) |
| Previous myocardial infarction | 104 (8.5%) | 3443 (6.7%) |
| Chronic pulmonary disease | 291 (23.9%) | 10 431 (20.3%) |
| Cerebrovascular disease | 174 (14.3%) | 6936 (13.5%) |
| Haemiplegia | 5 (0.4%) | 335 (0.7%) |
| Dementia | 17 (1.4%) | 1246 (2.4%) |
| Connective tissue disease | 109 (8.9%) | 1425 (2.8%) |
| Peptic ulcer disease | 118 (9.7%) | 3064 (6.0%) |
| Diabetes 1 and 2 | 106 (8.7%) | 4024 (7.8%) |
| Diabetes with end organ damage | 65 (5.3%) | 2155 (4.2%) |
| Moderate to severe renal disease | 83 (6.8%) | 1967 (3.8%) |
| Any tumour | 146 (12.0%) | 6914 (13.5%) |
| Leukaemia | 13 (1.1%) | 670 (1.3%) |
| Lymphoma | 21 (1.8%) | 1160 (2.3%) |
| Metastatic solid tumour | 32 (2.6%) | 1568 (3.1%) |
| Mild liver disease | 16 (1.3%) | 757 (1.5%) |
| Moderate-to-severe liver disease | 4 (0.3%) | 231 (0.5%) |
| AIDS | <3 | 70 (0.1%) |
| Alcoholism-related disorders | 17 (1.4%) | 2411 (4.7%) |
| Comorbidity Index (level of Charlson Index Score) | ||
| Low (0) | 391 (32.1%) | 21 487 (41.8%) |
| Medium (1–2) | 543 (44.5%) | 19 514 (38.0%) |
| High (≥3) | 286 (23.4%) | 10 356 (20.2%) |
| Duration of hospital stay, median | 6 (3–10) | 6 (3–10) |
| Systemic antibiotic therapy before admission | 445 (36.5%) | 17 094 (33.3%) |