Table 2.
Mean (standard deviation) and sample size of long-term air pollution exposures and cortisol in MESA Stress Studies
| Stress I | Stress II | Sample in pooled cross-section | Sample in longitudinal analysis | ||
|---|---|---|---|---|---|
| At Stress I | At Stress II | ||||
| Annual average air pollution concentrations | |||||
| Ambient PM2.5 (μg/m3) | 16.2 (2.1) | 11.7 (1.7) | 13.9 (3.0) | 16.1 (2.1) | 12.2 (1.5) |
| Individual PM2.5 (μg/m3) | 12.3 (2.1) | 8.5 (2.0) | 10.3 (2.8) | 12.3 (2.1) | 9.2 (1.5) |
| NOx (ppb) | 64.9 (17.5) | 38.5 (16.6) | 51.2 (21.5) | 65.4 (17.8) | 44.5 (13.7) |
| NO2 (ppb) | 28.2 (4.8) | 20.5 (7.5) | 24.2 (7.4) | 28.3 (4.9) | 23.8 (5.1) |
| Black Carbon (10−5/m) | 1.3 (0.2) | 1.1 (0.3) | 1.2 (0.3) | 1.3 (0.2) | 1.3 (0.2) |
| Cortisol | |||||
| N personsa | 867 | 926 | 1793 | 491 | 491 |
| N daysb | 2573 | 1847 | 4420 | 1467 | 978 |
| N samplesc | 14646 | 13811 | 28457 | 8422 | 7365 |
| Average salivary cortisol (nmol/L) | 10.3 (10.6) | 9.1 (9.2) | 10.9 (10.9) | ||
| Wake up cortisol (nmol/L) | 15.4 (10.9) | 13.4 (9.2) | 16.8 (10.7) | ||
| Wake-to-bed slope (mean (SE)) | −0.83 (0.01) | −0.91 (0.02) | −0.77 (0.02) | ||
| Area under the curve (mean (SE)) | 1.7 (0.02) | 1.5 (0.2) | 1.7 (0.3) | ||
a
Participants on hormone replacement therapy, inhaled or oral steroids or missing air pollution predictions were excluded.
b
Days with no time since wake-up recorded for the entire day or no cortisol values for the entire day were excluded.
c
Samples with missing cortisol values, time sample was taken, or unreliable cortisol values (>100 or 0 nmol/L) were excluded.