Table 4. Cox proportional hazard ratio with 95% CI of incident hospitalized HFrEF events by quartiles of baseline RMSSD, SDNN and rHR.

Quartiles	HFrEF (n = 27,235)
	n	Person-years	Rate per 1000 person-years (95% CI)	Model 1 HR (95% CI)	Model 2 HR (95% CI)	Model 3 HR (95% CI)
RMSSD (ms)
Q1 (1.24–10.51)	197	99,599	1.97 (1.71–2.27)	1.39 (1.12–1.73)*	1.14 (0.90–1.43)	1.13 (0.90–1.43)
Q2	170	103,503	1.64 (1.41–1.90)	1.22 (0.97–1.52)	1.06 (0.84–1.34)	1.05 (0.83–1.33)
Q3	143	111,784	1.27 (1.08–1.50)	1.02 (0.81–1.29)	0.95 (0.74–1.21)	0.97 (0.76–1.24)
Q4 (ref) (25.61–361.23)	144	116,198	1.23 (1.05–1.45)	1	1	1
P-trend				0.003	0.278	0.308
SDNN (ms)
Q1 (0.91–10.19)	212	99,503	2.13 (1.85–2.43)	1.48 (1.20–1.83)*	1.21 (0.96–1.52)	1.19 (0.95–1.50)
Q2	158	105,030	1.50 (1.28–1.75)	1.13 (0.90–1.42)	1.02 (0.80–1.30)	1.01 (0.79–1.28)
Q3	144	111,896	1.28 (1.09–1.51)	1.02 (0.81–1.28)	0.96 (0.75–1.22)	0.93 (0.73–1.19)
Q4 (ref) (24.17–313.20)	140	114,656	1.22 (1.03–1.43)	1	1	1
P-trend				<0.001	0.145	0.176
rHR (bpm)
Q1 (Ref) (33–59)	143	112,311	1.27 (1.07–1.49)	1	1	1
Q2	130	104,443	1.24 (1.04–1.47)	0.99 (0.78–1.26)	0.95 (0.74–1.23)	0.96 (0.75–1.24)
Q3	163	108,612	1.50 (1.28–1.74)	1.20 (0.96–1.50)	1.01 (0.79–1.29)	1.01 (0.79–1.29)
Q4 (73–123)	218	105,718	2.06 (1.80–2.35)	1.74 (1.41–2.15)*	1.33 (1.05–1.68)*	1.33 (1.05–1.68)*
P-trend				0.017	0.008	0.008

Model 1: adjusted for age and race

Model 2: Model 1 + adjusted for smoking status, alcohol, education, physical activity, BMI, hyperlipidemia, hypertension, diabetes mellitus, LVH, beta-blocker use, calcium channel blocker use, hormone therapy use

Model 3: model 2 + adjusted for time-varying incident CHD

Bpm: beats per minute; HFrEF: heart failure with reduced ejection fraction; ms: millisecond; SDNN: standard deviation of normal-to-normal RR interval; RMSSD: root mean square of successive difference of RR intervals; rHR: resting heart rate

*p < 0.05