Table 2.
Descriptive statistics of day 1 and day 2 cortisol measures and time of sampling of participants from the Speedwell study at phase 5.
| Pre-stress baseline (sample 1, ng/ml) | Post-cognitive test (sample 2, ng/ml) | Post-venepuncture (sample 3, ng/ml) | Post-stress recovery (sample 4, ng/ml) | Response to cognitive test (ng/ml) | Response to venepuncture (ng/ml) | ||
|---|---|---|---|---|---|---|---|
| Day 1 AM (9:00–11:59) | |||||||
| n | 495 | 491 | 486 | 476 | 486 | 475 | |
| Cortisol | Mean (SD) | 13.92 (12.25) | 13.69 (14.31) | 10.96 (13.03) | 10.67 (14.73) | -0.16 (13.46) | -2.75 (13.79) |
| Median (IQR) | 10.68 (5.84, 17.16) | 9.77 (5.38, 16.92) | 8.00 (4.11, 13.47) | 6.35 (3.69, 11.95) | -0.59 (−4.60, 3.66) | -1.80 (−5.71, 0.70) | |
| Time (h) | Mean (SD) | 10.38 (0.68) | 11.15 (0.68) | 11.77 (0.70) | 13.53 (1.13) | ||
| Day 1 PM (12:00–16:00) | |||||||
| n | 314 | 311 | 306 | 297 | 303 | 303 | |
| Cortisol | Mean (SD) | 10.99 (12.36) | 14.08 (22.29) | 10.43 (16.62) | 8.88 (13.70) | 3.35 (18.90) | -3.78 (21.22) |
| Median (IQR) | 7.04 (4.43, 13.50) | 7.79 (4.61, 16.05) | 6.15 (3.56, 11.88) | 5.04 (2.83, 9.21) | 0.28 (−2.35, 4.61) | -1.43 (−4.67, 0.51) | |
| Time (h) | Mean (SD) | 14.31 (0.68) | 15.11 (0.74) | 15.69 (0.76) | 17.33 (0.86) | ||
| P-value | < 0.001 | 0.05 | 0.05 | 0.004 | < 0.001 | 0.92 | |
| Wake + 30 min (sample 5, ng/ml) | 10:00 (sample 6, ng/ml) | 15:00 (sample 7, ng/ml) | 22:00 (sample 8, ng/ml) | Circadian slope (ng/ml/h) | AUC (ng) | ||
| Day 2 | |||||||
| n | 794 | 802 | 801 | 795 | 780 | 766 | |
| Cortisol | Mean (SD) | 28.00 (30.28) | 15.65 (21.94) | 9.96 (14.85) | 6.24 (13.79) | -1.50 (2.09) | 173.06 (169.63) |
| Median (IQR) | 19.52 (9.91, 35.33) | 10.49 (6.02, 17.70) | 6.57 (3.48, 11.41) | 3.12 (1.79, 6.05) | -1.02 (−2.04, −0.38) | 131.52 (79.38, 213,51) | |
| Time (h) | Mean (SD) | 7.51 (0.99) | 10.13 (0.45) | 15.16 (0.52) | 22.10 (0.41) | ||
Descriptive statistics of day 1 cortisol measures stratified by time of clinic attendance (AM and PM). Data are reported as number (n), mean (standard deviation, SD), median (interquartile range, IQR) for cortisol measures and mean (SD) for time of sampling. P-values are from linear regression analysis of the associatione between time of clinic visit and day 1 log-transformed cortisol measures adjusted for cortisol assay batch, time of sample, results of venepuncture and age at phase 5. AUC: area under curve.