Table 4.

Linear regression analyses predicting night RMSSD with occupational stress and cardiorespiratory fitness.

	ΔR2	β	p	ΔR2	β	p	ΔR2	β	p
Step 1	0.29		0.000	0.29		0.000	0.31		0.000
Years of service		-0.01	0.905		-0.01	0.905		-0.01	0.947
Age		-0.51	0.000		-0.51	0.000		-0.52	0.000
Shift work		-0.05	0.553		-0.05	0.553		-0.07	0.381
Step 2	0.00		0.384	0.02		0.048	0.00		0.872
Occupational stress
JDC ratio		0.07	0.384
ERI ratio					-0.14	0.048
Feelings of stress								0.00	0.872
Step 3	0.02			0.02		0.006	0.03		0.002
Cardiorespiratory fitness class		0.12	0.006		0.12	0.006		0.17	0.002
Step 4	0.00		0.839	0.00		0.902	0.01		0.092
Occupational stress ×		-0.04	0.839		0.01	0.902		0.11	0.092
cardiorespiratory fitness class

JDC, Job Demand Control; ERI, Effort Reward Imbalance; RMSSD, Root Mean Squares of Successive N-N Differences.