Table 2.

Associations between pre-diagnostic plasma osteoprotegerin quartiles and invasive breast cancer in a matched case-control study nested within the Nurses’ Health Study II.

Osteoprotegerin (pmol/L)	No. of Cases	No. of Controls	Odds Ratio (95% CI)	P-value 1
Model A2
Quartile 1 (0.4-3.1)	85	75	Reference	--
Quartile 2 (3.1-3.6)	80	74	0.93 (0.61, 1.44)	0.76
Quartile 3 (3.7-4.3)	72	74	0.84 (0.52, 1.35)	0.47
Quartile 4 (4.3-10.0)	60	74	0.67 (0.41, 1.11)	0.12
P-trend3				0.11
Model B4
Quartile 1 (0.4-3.1)	85	75	Reference	--
Quartile 2 (3.1-3.6)	80	74	1.07 (0.68, 1.69)	0.76
Quartile 3 (3.7-4.3)	72	74	0.92 (0.56, 1.51)	0.75
Quartile 4 (4.3-10.0)	60	74	0.79 (0.46, 1.33)	0.37
P-trend3				0.30
Model C5
Quartile 1 (0.4-3.1)	85	75	Reference	--
Quartile 2 (3.1-3.6)	80	74	1.07 (0.68, 1.69)	0.77
Quartile 3 (3.7-4.3)	72	74	0.92 (0.56, 1.52)	0.75
Quartile 4 (4.3-10.0)	60	74	0.78 (0.46, 1.33)	0.37
P-trend3				0.30

¹P-value produced using the Wald test.

²Model A: Accounting for matching factors only.

³P-trend modeling the median of each quartile as a continuous variable, testing for linearity using the Wald test.

⁴Model B: Model A plus adjustment for parity/age at first birth (categorical: nulliparous, 1-2 pregnancies/age first birth<25, 1-2 pregnancies/age first birth ≥25, ≥3 pregnancies/age first birth <25, ≥3 pregnancies/age first birth≥25), family history of breast cancer (categorical: yes, no), history of biopsy-confirmed benign breast disease (categorical: yes, no), BMI at age 18 (continuous: kg/m²), and average physical activity from 1989, 1991, and 1997 questionnaires (continuous: Metabolic Equivalent of Task [MET]-hrs/week).

⁵Model C: Model B plus adjustment for age at menarche (continuous: years), ever breastfed (categorical: yes, no), weight change between age 18 and blood collection (continuous: kg), and average alcohol consumption from 1991 and 1995 questionnaires (continuous: grams/day).

Abbreviations: CI=confidence interval; BMI=body mass index.