Table 3.
Estimated incidence rate ratios (IRR) (including 95% confidence intervals (CI)) by exposure variable categories on the number of ED re-presentations with mental health primary diagnosis within 1 year from a patient’s initial separation from negative binomial regression models (N=40 290)
| Univariate | Multivariable | Stepwise* | ||||
| IRR | 95% CI† | IRR | 95% CI† | IRR | 95% CI† | |
| Sociodemographic characteristics | ||||||
| Sex | ||||||
| Male | 1.00 | 1.00 | 1.00 | |||
| Female | 1.13 | (1.07 to 1.20) | 1.13 | (1.07 to 1.20) | 1.14 | (1.08 to 1.22) |
| Aboriginal and Torres Strait Islander | ||||||
| No | 1.00 | 1.00 | 1.00 | |||
| Yes | 1.27 | (1.16 to 1.39) | 1.23 | (1.13 to 1.35) | 1.21 | (1.10 to 1.33) |
| Age at first presentation (years) | ||||||
| 20–26 | 1.00 | 1.00 | 1.00 | |||
| 15–19 | 1.00 | (0.94 to 1.07) | 0.96 | (0.90 to 1.02) | 0.96 | (0.90 to 1.02) |
| 8–15 | 1.18 | (1.08 to 1.29) | 1.09 | (1.00 to 1.19) | 1.10 | (1.00 to 1.20) |
| Rurality or remoteness | ||||||
| Major cities | 1.00 | 1.00 | 1.00 | |||
| Inner regional | 1.08 | (1.01 to 1.16) | 1.15 | (1.07 to 1.24) | 1.16 | (1.08 to 1.25) |
| Outer regional or remote or very remote | 0.99 | (0.86 to 1.15) | 1.04 | (0.90 to 1.20) | 1.03 | (0.88 to 1.20) |
| SEIFA quartile | ||||||
| Most disadvantage: first (816–940) | 1.00 | 1.00 | 1.00 | |||
| Second (942–971) | 1.03 | (0.95 to 1.12) | 1.06 | (0.98 to 1.15) | 1.05 | (0.97 to 1.14) |
| Third (972–1038) | 0.97 | (0.89 to 1.06) | 1.02 | (0.93 to 1.12) | 1.01 | (0.92 to 1.10) |
| Least disadvantage: fourth (1039–1155) | 1.01 | (0.94 to 1.10) | 1.11 | (1.02 to 1.21) | 1.11 | (1.01 to 1.21) |
| Characteristics of the initial ED presentation | ||||||
| ED primary diagnosis | ||||||
| Anxiety | 1.00 | 1.00 | 1.00 | |||
| Depression | 1.27 | (1.15 to 1.40) | 1.16 | (1.05 to 1.28) | 1.18 | (1.06 to 1.30) |
| General mental health problem | 1.49 | (1.37 to 1.62) | 1.38 | (1.27 to 1.51) | 1.36 | (1.24 to 1.49) |
| Suicidal | 1.62 | (1.47 to 1.79) | 1.40 | (1.26 to 1.55) | 1.39 | (1.25 to 1.55) |
| Self-harm | 1.85 | (1.65 to 2.08) | 1.64 | (1.46 to 1.85) | 1.67 | (1.48 to 1.89) |
| Others | 1.65 | (1.51 to 1.81) | 1.49 | (1.35 to 1.64) | 1.48 | (1.34 to 1.64) |
| Mode of arrival | ||||||
| Arrived on own | 1.00 | 1.00 | 1.00 | |||
| Ambulance | 1.19 | (1.11 to 1.27) | 1.11 | (1.04 to 1.18) | 1.13 | (1.06 to 1.21) |
| Police | 1.04 | (0.93 to 1.18) | 0.97 | (0.86 to 1.10) | 0.97 | (0.85 to 1.10) |
| Others | 0.98 | (0.61 to 1.58) | 0.90 | (0.56 to 1.45) | 1.02 | (0.63 to 1.65) |
| Source of referral | ||||||
| Others | 1.00 | 1.00 | ||||
| Self/family/friend | 0.96 | (0.88 to 1.04) | 1.01 | (0.93 to 1.10) | ||
| Level of clinical facility | ||||||
| 1 or 2 | 1.00 | 1.00 | ||||
| 3 or 4 | 1.00 | (0.84 to 1.20) | 0.96 | (0.81 to 1.13) | ||
| 5 or 6 | 1.02 | (0.86 to 1.22) | 0.96 | (0.81 to 1.14) | ||
| Triage | ||||||
| 4 or 5 | 1.00 | 1.00 | 1.00 | |||
| 3 | 1.22 | (1.16 to 1.29) | 1.10 | (1.00 to 1.20) | 1.10 | (1.03 to 1.18) |
| 1 or 2 | 1.16 | (1.07 to 1.25) | 0.99 | (0.90 to 1.09) | 1.00 | (0.90 to 1.10) |
| Admitted to the hospital | ||||||
| No | 1.00 | 1.00 | 1.00 | |||
| Yes | 1.33 | (1.25 to 1.42) | 1.42 | (1.15 to 1.76) | 1.21 | (1.12 to 1.30) |
| Left at own risk | ||||||
| No | 1.00 | 1.00 | 1.00 | |||
| Yes | 1.23 | (1.09 to 1.40) | 1.56 | (1.24 to 1.95) | 1.31 | (1.14 to 1.51) |
| Completed treatment | ||||||
| Yes | 1.00 | 1.00 | ||||
| No | 1.29 | (1.21 to 1.37) | 1.21 | (0.97 to 1.50) | ||
| Transferred to another hospital | ||||||
| No | 1.00 | 1.00 | ||||
| Yes | 1.09 | (0.97 to 1.22) | 1.20 | (0.98 to 1.46) | ||
| Arrival time of day | ||||||
| 08:00–17:59 | 1.00 | 1.00 | 1.00 | |||
| 00:00–07:59 | 0.83 | (0.76 to 0.91) | 0.81 | (0.74 to 0.88) | 0.80 | (0.73 to 0.89) |
| 18:00–23:59 | 1.06 | (0.99 to 1.13) | 1.03 | (0.96 to 1.10) | 1.03 | (0.97 to 1.10) |
| Departure day of week | ||||||
| Friday–Sunday | 1.00 | 1.00 | 1.00 | |||
| Monday–Thursday | 1.11 | (1.04 to 1.18) | 1.08 | (1.02 to 1.15) | 1.08 | (1.02 to 1.15) |
| First episode length of stay (min) | ||||||
| <180 (3 hours) | 1.00 | 1.00 | 1.00 | |||
| 180–480 (3–8 hours) | 1.17 | (1.10 to 1.25) | 1.09 | (1.02 to 1.17) | 1.10 | (1.03 to 1.18) |
| 460+ (8+ hours) | 1.45 | (1.34 to 1.58) | 1.25 | (1.14 to 1.37) | 1.26 | (1.14 to 1.38) |
*Stepwise regression results include only covariates which were found to be significant at α=5%.
† CI is also used to assess the significance of the IRR coefficient, where if 1 is not inside the estimated CI, then it is concluded to be significantly associated with either significantly lower (if limits are <1) or higher (if limits are >1) re-presentation rate at α=5%.
ED, emergency department; IRR, incidence rate ratio.