Table 2.
Baseline characteristics by quartiles of ferritin in women in the subcohort (n=9,485)
| Ferritin quartiles (Range of ferritin, μg/L) | p for difference across quartiles* | Overall subcohort | |||||
|---|---|---|---|---|---|---|---|
| Q1 (1-29) | Q2 (30-58) | Q3 (59-107) | Q4 (108-3017) | ||||
| Age (years) | 47.2 (8.0) | 50.0 (9.4) | 54.1 (8.7) | 57.0 (7.8) | <0.001 | 52.1 (9.3) | |
| BMI (kg/m2) | 25.5 (4.4) | 25.4 (4.6) | 25.4 (4.4) | 26.4 (4.6) | <0.001 | 25.7 (4.5) | |
| Education (%) | 0.002 | ||||||
| Low | 12.4 | 10.2 | 7.3 | 6.3 | 8.9 | ||
| Primary | 33.1 | 30.5 | 32.6 | 34.2 | 32.8 | ||
| Vocational | 20.3 | 22.0 | 24.4 | 26.6 | 23.4 | ||
| Secondary | 15.6 | 16.6 | 18.0 | 17.0 | 16.6 | ||
| Higher | 18.6 | 20.7 | 17.8 | 15.9 | 18.3 | ||
| Physical Activity (%) | 0.0008 | ||||||
| Inactive | 30.1 | 26.4 | 26.8 | 24.5 | 27.0 | ||
| Moderately inactive | 34.2 | 35.4 | 34.8 | 36.2 | 35.1 | ||
| Moderately active | 20.3 | 20.9 | 20.4 | 21.1 | 20.9 | ||
| Active | 15.4 | 17.3 | 18.0 | 18.2 | 17.1 | ||
| Smoking (%) | 0.0006 | ||||||
| Never | 59.7 | 54.6 | 54.1 | 56.2 | 56.0 | ||
| Former | 20.2 | 21.3 | 21.7 | 22.4 | 21.4 | ||
| Smoker | 20.1 | 24.1 | 24.3 | 21.4 | 22.6 | ||
| Family history of T2D (%) | 19.7 | 18.7 | 19.5 | 23.5 | 0.1 | 20.5 | |
| Alcohol intake (g/day) † | 1.7 (0;7.2) | 2.7 (0.2;10.6) | 3.6 (0.4;12.0) | 5.1 (0.6;13.5) | <0.001 | 3.0 (0.2;11.1) | |
| Estimated dietary iron intake (mg/day) | 12.3 (3.6) | 12.4 (3.7) | 12.3 (3.6) | 12.0 (3.4) | 0.009 | 12.2 (3.6) | |
| Biomarkers (mean, SD) | |||||||
| TSAT (%) | 20.8 (10.5) | 27.2 (9.7) | 28.5 (9.0) | 30.5 (10.3) | <0.001 | 26.7 (10.5) | |
| Iron (μmol/L) | 14.3 (6.7) | 17.1 (6.0) | 17.3 (5.4) | 17.8 (5.8) | <0.001 | 16.6 (6.2) | |
| Transferrin (g/L) | 3.1 (0.5) | 2.8 (0.4) | 2.7 (0.4) | 2.6 (0.4) | <0.001 | 2.8 (0.4) | |
| Glucose (mmol/L) | 4.7 (1.3) | 4.7 (1.0) | 4.8 (1.2) | 5.0 (1.3) | <0.001 | 4.8 (1.2) | |
| HbA1c (mmol/mol) | 35.6 (4.6) | 35.5 (4.3) | 36.4 (4.7) | 36.9 (5.8) | <0.001 | 36.1 (4.9) | |
| hsCRP (mg/L) † | 0.9 (0.4;1.9) | 1.0 (0.5;2.2) | 1.1 (0.6;2.5) | 1.4 (0.7;3.1) | <0.001 | 1.1 (0.5;2.4) | |
| ALT (U/L) | 17.0 (8.7) | 17.7 (9.0) | 19.5 (12.4) | 21.9 (15.1) | <0.001 | 19.0 (11.7) | |
| AST (U/L) | 25.7 (9.9) | 26.1 (10.1) | 27.3 (7.9) | 29.1 (13.7) | <0.001 | 27.1 (10.7) | |
| GGT (U/L) † | 14.0 (11.0;18.0) | 16.0 (12.0; 22.0) | 18.0 (14.0;26.0) | 20.0 (15.0;31.0) | <0.001 | 17.0 (13.0;24.0) | |
Data shown are mean (standard deviation) or median (interquartile range) for skewed variables marked †
*
ANOVA for normally distributed continuous variables, Kruskal-Wallis test for continuous variables with skewed distribution (†) and Chi2 for categorical variables