Table 4.
Adjusted RRs (95% CI) for incidence of GDM in relation to irregular and long menstrual cycles in mid-adulthood (age 29–46 years), stratified by BMI at age 18 years and in 1993 (NHS II, 1993–2009)
| BMI at age 18 yearsa (RRs 95% CI) | BMI in 1993b (RRs 95% CI) | |||||
|---|---|---|---|---|---|---|
| <25 kg/m2 (GDM=502) | ≥25 kg/m2 (GDM=76) |
<25 kg/m2 (GDM=305) |
≥25 kg/m2 (GDM=273) |
|||
| Regularity | ||||||
| OC user | 1.09 (0.88, 1.35) | 1.60 (0.93, 2.75) | 1.18 (0.90, 1.54) | 1.20 (0.89, 1.62) | ||
| Very regular | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | ||
| Regular | 1.01 (0.80, 1.28) | 0.99 (0.47, 2.07) | 0.92 (0.67, 1.26) | 1.09 (0.79, 1.51) | ||
| Usually irregular | 0.83 (0.52, 1.32) | 1.30 (0.51, 3.29) | 0.67 (0.34, 1.32) | 1.12 (0.65, 1.91) | ||
| Always irregular/no period | 1.61 (1.13, 2.30) | 1.97 (1.03, 3.76) | 1.70 (1.01, 2.86) | 1.84 (1.25, 2.70) | ||
| p for interactionc | 0.19 | 0.29 | ||||
| Length (days) | ||||||
| OC users | 1.18 (0.95, 1.46) | 1.85 (1.06, 3.24) | 1.37 (1.05, 1.80) | 1.21 (0.90, 1.63) | ||
| ≤25 | 1.30 (0.94, 1.80) | 1.67 (0.69, 4.06) | 1.52 (1.02, 2.28) | 1.18 (0.75, 1.88) | ||
| 26–31 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | ||
| ≥32 or too irregular to estimate | 1.37 (1.09, 1.72) | 1.91 (1.08, 3.35) | 1.52 (1.11, 2.07) | 1.36 (1.02, 1.81) | ||
| p for interactionc | 0.41 | 0.86 | ||||
Multivariable model was adjusted for age (continuous), age at menarche (continuous), ethnicity (white or others), family history of diabetes (yes or no) and parity (1, 2, 3 or ≥4), as well as time-varying alcohol consumption (0, 0.1–5.0 or ≥5.1 g/day), BMI (<23, 23–24.9, 25–29.9, 30–34.9 or ≥35 kg/m2), physical activity (<150 or ≥150 min/week), smoking status (never, past or current) and AHEI 2010 score (below or above median) during follow-up
Multivariable model was adjusted for age (continuous), age at menarche (continuous), BMI at age 18 years (continuous), ethnicity (white or others), family history of diabetes (yes or no) and parity (1, 2, 3 or ≥4), as well as time-varying alcohol consumption (0, 0.1–5.0 or ≥5.1 g/day), physical activity (<150 or ≥150 min/week), smoking status (never, past or current) and AHEI 2010 score (below or above median) during follow-up
p for interaction as tested by excluding women reporting OC use