Plasma 25-Hydroxyvitamin D and 1,25-Dihydroxyvitamin D and Risk of Breast Cancer

NOTE: For 25(OH)D, quintile cut points for batch 1 were ≤20, 21 to 28, 29 to 33, 34 to 39, and ≥40 ng/mL; for batch 2, ≤28, 29 to 34, 35 to 39, 40 to 47, and ≥48 ng/mL; and for batch 3, ≤18, 19 to 24, 25 to 29, 30 to 36, and ≥37 ng/mL. For 1,25(OH)₂D, quintile cut points were ≤28.5, 28.6 to 31.5, 31.6 to 34.3, 34.4 to 38.1, and ≥38.2 ng/mL.

↵* Conditional logistic regression, adjusted for matching factors (age, fasting status at blood draw, month of blood collection, time of day of blood collection, menopausal status, and current use of postmenopausal hormones).

↵† Conditional logistic regression, adjusted for matching factors, BMI at age 18 (<19, 19-20.9, 21-22.9, 23-24.9, ≥25 kg/m²), parity/age at first birth (nulliparous, 1-4 children/age at first birth <25 years, 1-4 children/age at first birth 25-29 years, 1-4 children/age at first birth ≥30 years, ≥5 children/age at first birth <25years, ≥5 children/age at first birth ≥25 years), family history of breast cancer (no family history, history in mother or sister), history of benign breast disease (no, yes), postmenopausal hormone use (continuous, in months), age at menarche (<12, 12, 13 or ≥14 years), age at menopause (<45, 45-49, 50-55, >55 years), alcohol intake (0, 1-2, 3-6, 7-13, ≥14 drinks per week), and plasma α-carotene (batch-specific quintiles).

↵‡ For 25(OH)D, analyses includes 469 cases and their matched controls. For 1,25(OH)₂D, analyses includes 443 cases and their matched controls. Adjusted for all factors in multivariable model above.

↵§ Two-sided P_trend over quintiles, calculated by using the median value of each quintile as a continuous variable in the multivariable model.