Table 2. Risk of ovarian cancer by use of oral contraceptives using conditional logistic regression and generalised estimating equations, Breast Cancer Family Registry.

	Conditional logistic		GEE		GEE
	Cases with unaffected sister controls		Cases with unaffected sister controls		All cases and all controls
	Age-adjusted model	Multivariable modela	Age-adjusted model	Multivariable modelb	Multivariable modelc
	OR (95% CI)	OR (95% CI)	OR (95% CI)	OR (95% CI)	OR (95% CI)
Oral contraceptive use
Never	Ref	Ref	Ref	Ref	Ref
Ever	0.51 (0.23, 1.15)	0.52 (0.23, 1.17)	0.71 (0.47, 1.06)	0.58 (0.37, 0.91)	0.35 (0.27, 0.45)
Duration of oral contraceptive use (years)
0	Ref	Ref	Ref	Ref	Ref
< 3	0.77 (0.32, 1.85)	0.85 (0.34, 2.10)	1.16 (0.68, 1.97)	0.99 (0.54, 1.80)	0.41 (0.30, 0.55)
3 to <6	0.18 (0.04, 0.88)	0.19 (0.04, 0.90)	0.30 (0.10, 0.88)	0.27 (0.09, 0.83)	0.23 (0.15, 0.38)
⩾ 6	0.26 (0.08, 0.84)	0.26 (0.08, 0.83)	0.44 (0.23, 0.84)	0.33 (0.16, 0.67)	0.34 (0.24, 0.49)
P–value for trend	<0.01	<0.01	<0.01	<0.01	<0.01
Age at first oral contraceptive use (years)
Never	Ref	Ref	Ref	Ref	Ref
<20	0.66 (0.18, 2.47)	0.68 (0.18, 2.56)	0.87 (0.48, 1.57)	0.71 (0.37, 1.39)	0.26 (0.18, 0.39)
20–25	0.20 (0.06, 0.68)	0.21 (0.06, 0.71)	0.45 (0.24, 0.82)	0.35 (0.18, 0.66)	0.26 (0.19, 0.37)
>25	0.61 (0.19, 1.96)	0.61 (0.19, 1.96)	0.66 (0.28, 1.57)	0.55 (0.23, 1.30)	0.46 (0.31, 0.69)
P– value for trend	0.07	0.07	0.03	<0.01	<0.01

^aAdjusted for age, parity.

^bAdjusted for age, race, parity, age at last birth.

^cAdjusted for age, race, parity.