Table 4. Hazard ratio for ICU admission within three weeks after admission.

	Cox regression				Cox regression
	Unadjusted	Model 1	Model 2		Unadjusted	Model 1	Model 2
SDNN				RMSSD
≤ 8	reference	reference	reference	≤ 8	reference	reference	reference
> 8	0.62 (0.37–1.03)	0.65 (0.39–1.09)	0.65 (0.39–1.08)	> 8	0.46 (0.27–0.80)	0.51 (0.29–0.90)	0.51 (0.29–0.90)

Model 1 adjusted for age.

Model 2 adjusted for age and cardiac disease.

Note: ICU = intensive care unit, SDNN = standard deviation of normal to normal heartbeat intervals, RMSSD = root mean square of successive differences between adjacent heartbeats. Both SDNN and RMSSD cut-offs are in msec.