TABLE 4

Unadjusted and multivariable adjusted relative hazards (95% CIs) of incident metabolic syndrome and duration of lactation categories by GDM status (1986–2006)

Models1 or more non-GDM births, referent: 0–1 month lactation (n = 157)1 or more GDM births, referent: 0–1 month lactation (n = 22)
Lactation durationP*Lactation durationP*
>1–5 months6–9 months>9 months>1–5 months6–9 months>9 months
n157152154171728
Unadjusted0.49 (0.29–0.82)0.40 (0.23–0.71)0.41 (0.23–0.72)<0.0010.24 (0.08–0.75)0.28 (0.09–0.86)0.11 (0.03–0.39)0.001
Model 1 = study center, race, baseline covariates (age, education, and smoking), and time-dependent parity†0.54 (0.32–0.91)0.49 (0.28–0.88)0.54 (0.28–1.02)0.030.33 (0.10–1.03)0.34 (0.11–1.07)0.14 (0.04–0.53)0.01
Model 1 + baseline covariates: (BMI and all metabolic syndrome components)0.63 (0.37–1.08)0.52 (0.29–0.93)0.45 (0.24–0.87)0.040.54 (0.16–1.75)0.37 (0.11–1.24)0.14 (0.04–0.55)0.03
Fully adjusted model = model 1 + baseline covariates (BMI, all metabolic syndrome components) and baseline physical activity0.61 (0.36–1.05)0.52 (0.29–0.93)0.44 (0.23–0.84)0.030.56 (0.17–1.82)0.35 (0.11–1.16)0.14 (0.04–0.55)0.03
Fully adjusted model + time-dependent physical activity (mediator)0.67 (0.39–1.16)0.54 (0.30–0.98)0.51 (0.26–0.98)0.100.41 (0.12–1.35)0.27 (0.08–0.90)0.13 (0.03–0.52)0.02
Fully adjusted model + time-dependent weight gain (mediator)0.71 (0.41–1.24)0.35 (0.19–0.65)0.56 (0.29–1.09)0.010.49 (0.15–1.64)0.33 (0.09–1.14)0.09 (0.02–0.37)0.01
  • *Test of the overall association among lactation categories and incident metabolic syndrome within non-GDM and GDM birth groups.

  • †Time-dependent parity (continuous covariate) is the cumulative total number of births since baseline for each time interval through the end of follow-up.