Table 2.

Rate of invasive breast cancer among postmenopausal women (50-79 years old) enrolled in the Women's Health Initiative Observational Study (1993-2003)

Number of breast healthy behaviors participated in	FHLBC	Cases	Woman-years	Rate (per 10,000 woman-years)	Rate difference	Attributable proportion
All three	Yes	25	4,206	59	24	41%
	No	108	30,807	35
Two	Yes	95	17,136	55	14	25%
	No	544	130,438	42
One	Yes	182	29,020	63	23	36%
	No	901	225,716	40
None	Yes	25	3,585	70	23	33%
	No	117	25,002	47

The women are stratified by family history of breast cancer (in a first-degree relative at the age of 45 years or more) and the degree of participation in behaviors recommended for breast cancer-preventive behaviors. To focus on the comparison of greatest contrast, women exhibiting partial adherence were excluded from the following calculation: interaction contrast = [R_{BHB = all three, FHLBC = 1} - R_{BHB = all three, FHLBC = 0}] - [R_{BHB = none, FHLBC = 1} - R_{BHB = none, FHLBC = 0}] = 0.0001; 95% confidence interval = -0.0036, 0.0039. FHLBC, family history of later-onset breast cancer.