TABLE 2.
HRs (95% CIs) of T2DM risk in relation to habitual intakes of total iron and supplemental iron in women with a history of GDM1
| Iron intake |
|||||
| First Q or category | Second Q or category | Third Q or category | Fourth Q or category | P-trend | |
| Total iron intake,2 mg/d | 11.6 | 14.9 | 21.1 | 37.2 | — |
| T2DM cases, n | 139 | 171 | 165 | 166 | — |
| Person-years | 14,431 | 14,436 | 14,405 | 14,411 | — |
| Age-adjusted model | 1.00 (reference)3 | 1.23 (0.96, 1.58) | 1.05 (0.81, 1.35) | 1.22 (0.95, 1.57) | 0.28 |
| Multivariable model | 1.00 (reference) | 1.48 (1.11, 1.97) | 1.33 (0.98, 1.80) | 1.64 (1.20, 2.25) | 0.02 |
| Supplemental iron intake, mg/d | 0 | 0.1–29.9 | ≥30 | — | — |
| T2DM cases, n | 252 | 340 | 49 | — | — |
| Person-years | 26,942 | 26,072 | 4669 | — | — |
| Age-adjusted model | 1.00 (reference) | 1.21 (1.01, 1.46) | 1.50 (1.07, 2.10) | — | 0.01 |
| Multivariable model | 1.00 (reference) | 1.47 (1.18, 1.84) | 1.83 (1.25, 2.70) | — | 0.002 |
In multivariate models, covariates included age (mo), parity (1, 2, 3, or ≥4), BMI [(in kg/m2) <23.0, 23.0–24.9, 25.0–26.9, 27.0–29.9, 30.0–34.9, or ≥35.0], age at first birth (12–24, 25–29, or ≥30 y), race-ethnicity (Caucasian, African American, Hispanic, Asian, or other), family history of diabetes (yes or no), oral contraceptive use (current, former, or never), menopausal status (premenopausal or postmenopausal), cigarette smoking (never, former, or current), alcohol intake (0, 0.1–4.9, 5.0–14.9, or ≥15.0 g/d), physical activity (quartiles), the ratio of polyunsaturated fat intake to saturated fat intake (quartiles), and intakes of total energy (quartiles), saturated fat (quartiles), trans fat (quartiles), dietary cholesterol (quartiles), animal protein (quartiles), vegetable protein (quartiles), glycemic load (quartiles), cereal fiber (quartiles), calcium (quartiles), magnesium (quartiles), and vitamin C (quartiles). For the analysis of supplemental iron, an adjustment for intakes of dietary iron was also performed. HRs (95% CIs) were estimated with the use of Cox proportional hazards models. Tests for a significant linear trend across quartiles (total iron intake) or categories (supplemental iron intake) were carried out by assigning median values of each quartile or category of iron intake as a continuous variable. GDM, gestational diabetes mellitus; Q, quartile; T2DM, type 2 diabetes mellitus.
All values are medians.
HR; 95% CI in parentheses (all such values).