Baseline population characteristics and measurements
| Day workers | Shift workers | p Value | |
| Population characteristics: | |||
| n | 32 | 75 | |
| Age (y, mean (SD)) | 29.3 (5.3) | 30.4 (6.7) | 0.4 |
| Sex (% female) | 9 | 11 | 0.81-150 |
| Smoking habits (%): | |||
| Never smoker | 48 | 41 | 0.41-150 |
| Current smoker | 26 | 40 | |
| Ex-smoker | 26 | 19 | |
| Education (%): | |||
| Low | 3 | 38 | 0.0011-150 |
| Intermediate | 35 | 44 | |
| High | 61 | 18 | |
| Baseline frequency of premature complexes: | |||
| PAC (beats/h, median) | 0.54 | 0.47 | NA |
| PAC (respondents with >1/h, %) | 30.9 | 38.7 | 0.41-151 |
| PVC (beats/h, median) | 0.043 | 0.042 | NA |
| PVC (respondents with >0.1/h, %) | 25.8 | 23.4 | 0.81-151 |
| Baseline heart rate variability: | |||
| Heart rate (beats/min) | 71.6 (8.4) | 75.3 (8.4) | 0.04 |
| SDNNi (ms) | 89.1 (28.7) | 74.6 (20.7) | 0.01 |
| Loglow (log ms) | −2.67 (0.18) | −2.76 (0.21) | 0.03 |
| Loghigh (log ms) | −2.98 (0.35) | −3.15 (0.30) | 0.03 |
| % lf | 65.1 (10.8) | 68.4 (8.1) | 0.2 |
↵1-150 p value by χ2 test.
↵1-151 p value by Wilcoxon two sample test.
PAC=premature atrial complexes; PVC=premature ventricular complexes; SDNNi=mean of all 5 minute SDs of NN intervals; Loglow=power in the low frequency range (0.05–015 Hz) in logarithmic units; Loghigh=power in the high frequency range (0.15–0.40 Hz) in logarithmic units; % lf=low frequency power (0.05–0.15 Hz) in normalised units.