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Table 5 Coding for predictor variables

From: Risk prediction for estrogen receptor-specific breast cancers in two large prospective cohorts

Predictor variable Coding
Menopausal status 0: premenopausal
1: postmenopausal
Age at menopause 0: premenopausal or ≤ 45 years
1: 45.1–50.0 years
2: 50.1–55.0 years
3: > 55.0 years
Breastfeeding 0: parous women who never breastfed and
nulliparous women
1: 0.1–6 months
2: 6.1–12 months
3: > 12 months
Age at menarche 0: ≤ 11 years
1: 12 years
2: 13 years
3: 14 years
4: ≥ 15 years
Hormone replacement therapy (HRT) use 0: never used HRT
1: 0.1–1 year
2: 1.1–2 years
3: 2.1–3 years
4: > 3 years
Full-term pregnancy (FTP) 0: nulliparous
1: parous
Number of FTPs 0: nulliparous or 1 FTP
1: 2 FTPs
2: ≥ 3 FTPs
Age a first FTP 0: nulliparous or ≤ 20 years
1: 20.1–25.0 years
2: 25.1–30.0 years
3: 30.1–35.0 years
4: > 35.0 years
Body mass index 0: < 25.0 kg/m2
1: 25–29.9 kg/m2
2: 30–34.9 kg/m2
3: > 35.0 kg/m2
Body height per 10-cm increment Body height in centimeters divided by 10, continuous variable
Alcohol intake 0: non-drinker
1: < 1 drink/day
2: 1.0–1.9 drinks/day
3: ≥ 2 drinks/day