Table 2. Rate ratio (RR) of recurrent subdural haematoma (SDH) within the first year and after the first year of follow-up, according to concomitant medical diseases and other potential predictors in Denmark 1996–2011.
| Potential predictors for recurrent SDH | <1 year | ≥1 year | P-value + | ||||
|---|---|---|---|---|---|---|---|
| Events | Adjusted RR ** | (95% CI*) | Events | Adjusted RR ** | (95% CI*) | ||
| Age (years) | |||||||
| 20–49 | 211 | 1 | (Ref.) | 44 | 1 | (Ref.) | 0.09 Ω |
| 50–69 | 452 | 1.13 | (0.96–1.34) | 59 | 0.95 | (0.64–1.41) | |
| 70- | 731 | 1.47 | (1.24–1.74) | 58 | 1.06 | (0.71–1.58) | |
| Gender | |||||||
| Males | 1042 | 1.63 | (1.44–1.84) | 115 | 1.43 | (1.03–2.04) | 0.50 |
| Females | 352 | 1 | (Ref.) | 46 | 1 | (Ref.) | |
| Alcohol addiction | |||||||
| Yes | 275 | 1.05 | (0.91–1.22) | 61 | 2.68 | (1.93–3.68) | < .0001 |
| No | 1119 | 1 | (Ref.) | 100 | 1 | (Ref.) | |
| Chronic liver disease | |||||||
| Yes | 63 | 1.16 | (0.88–1.50) | 12 | 2.71 | (1.41–4.70) | 0.02 |
| No | 1331 | 1 | (Ref.) | 149 | 1 | (Ref.) | |
| Coagulopathy | |||||||
| Yes | 14 | 1.17 | (0.66–1.91) | 1 | 1.31 | (0.07–5.83) | 0.92 |
| No | 1380 | 1 | (Ref.) | 160 | 1 | (Ref.) | |
| Surgical treatment | |||||||
| Yes | 856 | 1.77 | (1.58–1.98) | 101 | 1.61 | (1.17–2.24) | 0.59 |
| No | 538 | 1 | (Ref.) | 60 | 1 | (Ref.) | |
| Antihypertensive treatment | |||||||
| Yes | 440 | 0.92 | (0.81–1.04) | 40 | 1.13 | (0.78–1.60) | 0.29 |
| No | 954 | 1 | (Ref.) | 121 | 1 | (Ref.) | |
| Renal insufficiency | |||||||
| Yes | 34 | 1.18 | (0.82–1.64) | 2 | 1.23 | (0.20–3.87) | 0.95 |
| No | 1360 | 1 | (Ref.) | 159 | 1 | (Ref.) | |
| Diabetes mellitus | |||||||
| Yes | 90 | 1.44 | (1.14–1.79) | 3 | 0.76 | (0.19–2.00) | 0.23 |
| No | 1304 | 1 | (Ref.) | 158 | 1 | (Ref.) | |
| Previous cerebral ischemic infarction | |||||||
| Yes | 103 | 0.99 | (0.80–1.21) | 10 | 1.15 | (0.57–2.07) | 0.67 |
| No | 1291 | 1 | (Ref.) | 151 | 1 | (Ref.) | |
| Statins | |||||||
| Yes | 167 | 1.01 | (0.84–1.21) | 5 | 0.50 | (0.18–1.10) | 0.09 |
| No | 1227 | 1 | (Ref.) | 156 | 1 | (Ref.) | |
| Trauma diagnosis † | |||||||
| Yes | 832 | 1.12 | (1.00–1.25) | 95 | 1.36 | (0.99–1.87) | 0.25 |
| No | 562 | 1 | (Ref.) | 66 | 1 | (Ref.) | |
| PDMD †† | |||||||
| Yes | 26 | 0.94 | (0.62–1.37) | 4 | 4.06 | (1.25–9.64) | 0.02 |
| No | 1368 | 1 | (Ref.) | 157 | 1 | (Ref.) | |
* 95% Confidence interval
** Rate ratios adjusted for calendar period, time since admittance for first SDH, length of hospital stay for the primary bleeding, and potential predictors for recurrent SDH listed in Table 1.
+ P-value: Comparison of the RR’s within and after the first year, following the primary SDH.
Ω Homogeneity test
† Trauma diagnosis less than 2 years before the primary SDH
†† PDMD: Pre-packaged Daily Medication Doses.