Impacts of injury severity on long-term outcomes following motor vehicle crashes

BMC Public Health

Table 4 Mediation analysis for moderate-severe injury

	Total effect of LOS	Direct effect of LOS	Total of indirect effects of LOS^a
	Standardised beta coefficient (SE) ^b	Standardised beta coefficient (SE) [estimated % of total effect] ^b	Standardised beta coefficient (SE) [estimated % of total effect] ^b
Outcome: SF12 PCS at baseline
LOS2–6 days vs 1 day or less	− 0.70 (0.05)	− 0.53 (0.04) [70%]	− 0.17 (0.03) [30%]
LOS ≥7 days vs 1 day or less	− 0.98 (0.07)	−0.74 (0.06) [75%]	− 0.24 (0.04) [25%]
Outcome: SF12 PCS at 12 months
LOS2–6 days vs 1 day or less	− 0.24 (0.06)	0 (0.06) [Small or absent]	− 0.24 (0.03) [Predominantly or entirely indirect, estimated at 100%]
LOS > = 7 days vs 1 day or less	− 0.88 (0.09)	− 0.50 (0.09) [57%]	−0.38 (0.04) [43%]
Outcome: SF12 MCS at baseline
LOS2–6 days vs 1 day or less	− 0.13 (0.05)	− 0.02 (0.04) [Small or absent]	−0.11 (0.03) [Predominantly or entirely indirect, estimated at 87%]
LOS > = 7 days vs 1 day or less	− 0.24 (0.07)	− 0.07 (0.06) [Small or absent]	−0.17 (0.04) [Predominantly or entirely indirect, estimated at 71%]
Outcome: SF12 MCS at 12 months
LOS2–6 days vs 1 day or less	− 0.11 (0.06)	0.02 (0.06) [Small or absent]	− 0.12 (0.03) [Predominantly or entirely indirect, estimated at 91%]
LOS > = 7 days vs 1 day or less	− 0.25 (0.10)	− 0.03 (0.09) [Small or absent]	−0.22 (0.04) [Predominantly or entirely indirect, estimated at 87%]

^a Potential mediating factors for indirect effects of injury severity on SF12 included baseline pain, baseline psychological status and CTP claimant status. For SF12 outcomes at 12 months, the baseline value was also considered as a potential mediating factor
^b Estimated effects are standardised so that the beta coefficients describe standard deviations of SF12 PCS or SF12 MCS. Percentages for direct or indirect effects are shown when the confidence interval of the corresponding beta coefficient does not include 0

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