Poisson regression model of the relationship between clinical and demographic risk factors and consultation for recurrent boil or abscess, 1995–2011
| Factors associated with recurrent diagnosis | Crude rate per 1000 person-years (95% CI) | Unadjusted analysis IRR (95% CI) | Adjusted analysisa IRR (95% CI) |
|---|---|---|---|
| Mean age, years (SD) | 41 (20.1) | 41 (19.0) | |
| Follow-up time, person-years | 30 2257 | 416 556 | |
| Age, years | |||
| 16–24 | 122.2 (116.4 to 128.3) | 1 | 1 |
| 25–34 | 127.6 (122.8 to 132.6) | 1.0 (1.0 to 1.1) | 1.0 (0.9 to 1.1) |
| 35–44 | 121.6 (117.2 to 126.2) | 1.0 (0.9 to 1.1) | 0.9 (0.9 to 1.0) |
| 45–54 | 106.9 (102.2 to 111.9) | 0.9 (0.8 to 0.9) | 0.8 (0.8 to 0.9) |
| 55–64 | 89.2 (84.2 to 94.4) | 0.7 (0.7 to 0.8) | 0.7 (0.7 to 0.8) |
| 65–74 | 78.0 (72.4 to 84.0) | 0.6 (0.6 to 0.7) | 0.6 (0.6 to 0.7) |
| 75–89 | 65.9 (59.7 to 72.8) | 0.5 (0.5 to 0.6) | 0.6 (0.5 to 0.6) |
| Male | 97.3 (94.6 to 100.1) | 1 | 1 |
| Female | 115.1 (112.5 to 117.7) | 1.2 (1.1 to 1.2) | 1.1 (1.0 to 1.1) |
| BMI, kg/m2 | |||
| <30 | 100.9 (98.6 to 103.2) | 1 | 1 |
| ≥30 | 133.2 (128.8 to 137.6) | 1.3 (1.3 to 1.4) | 1.3 (1.2 to 1.3) |
| Diabetes | |||
| No | 104.7 (102.7 to 106.7) | 1 | 1 |
| Yes | 128.9 (122.9 to 135.2) | 1.2 (1.2 to 1.3) | 1.3 (1.2 to 1.3) |
| Skin disease | |||
| No | 105.4 (103.3 to 107.5) | 1 | 1 |
| Yes | 116.7 (112.2 to 121.5) | 1.1 (1.1 to 1.2) | 1.1 (1.0 to 1.1) |
| No prior antibiotics | 95.2 (93.1 to 97.4) | 1 | 1 |
| 1 course | 133.7 (129.1 to 138.4) | 1.4 (1.4 to 1.5) | 1.4 (1.3 to 1.4) |
| >1 course | 162.0 (152.7 to 171.8) | 1.7 (1.6 to 1.8) | 1.6 (1.5 to 1.7) |
| Smoker | |||
| No | 97.1 (94.8 to 99.5) | 1 | 1 |
| Yes | 135.0 (131.1 to 139.1) | 1.4 (1.2 to 1.4) | 1.3 (1.2 to 1.4) |
| P-value (LRTa) | <0.0001 | ||
↵a LRT comparing simple model (age, sex and bmi) to final model. BMI = body mass index. IRR = incidence rate ratio. LRT = Likelihood ratio test