Table I.
Clinical characteristics of study participants presented for winter and summer seasons and coefficients of variation determined by the reliability study performed.
| Variable | Winter season | Summer season | Pb | CV (%) |
|---|---|---|---|---|
| Temperature (°C) | 3.1 (4.4) | 10.9 (3.2) | – | |
| M/I (100 × mg × min-1 × kg-1/(mU × L-1)) | 4.84 (2.44) | 5.44 (2.53) | 0.0003 | 13.9 |
| HOMA-IR (pmol × mmol/L2) | 77.0 (56.0) | 81.0 (72.7) | 0.11 | 15.6 |
| Incremental area under insulin curve (pmol × min/L) | 1167 783 | 1003 (632) | 0.007 | 42.6 |
| Fasting plasma glucose (mmol/L) | 5.80 (1.52) | 5.71 (1.32) | 0.28 | 5.8 |
| 2-h plasma glucose (OGTT) (mmol/L) | 8.35 (4.03) | 8.27 (4.09) | 0.58 | 14.2 |
| Energy intake (kcal)a | 1735 456 | 1772 (467) | 0.22 | |
| Height (cm) | 174.8 (5.8) | 174.7 (6.4) | 0.88 | 0.0 |
| Weight (kg) | 80.7 (11.4) | 79.6 (11.9) | 0.18 | 0.8 |
| BMI (kg/m2) | 26.4 (3.4) | 26.0 (3.4) | 0.12 | 0.8 |
| Waist circumference (cm) | 95.0 (9.5) | 93.7 (9.7) | 0.03 | 2.3 |
| 25-Hydroxyvitamin D (nmol/L) | 66.5 (17.8) | 72.5 (20.7) | < 0.0001 | |
| Smoker (%) | 20.5 | 20.9 | 0.88 | |
| High usual leisure time physical activity (%) | 60.0 | 63.9 | 0.23 | |
| Type 2 diabetes (%) | 14.3 | 16.0 | 0.52 | |
| Impaired glucose tolerance (%) | 13.1 | 12.1 | 0.67 | |
| Diabetes medicine: per oral (%) | 5.3 | 3.4 | 0.15 | |
| Hypertension medicine: ACE inhibitors (%) | 6.1 | 6.1 | 0.99 | |
| Hypertension medicine: beta blockers (%) | 19.6 | 17.2 | 0.33 |
Data presented are: Mean (SD) or % for winter season (October–April), n = 810; and summer season (May–September), n = 307. Coefficients of variation (CV) from the reliability study, n = 20.
aData on energy intake is presented from a subset (winter season, n = 762; summer season, n = 288).
bAdjusted for age.