Table 6. Parameter estimates for the final model.

Parameter	BRCA1		BRCA2		Noncarriers
Allele frequency (95% Cl)	0.0006 (0.04–0.10%)		0.0010 (0.07–0.16%)		NA
Average penetrance (%) by the age of 70 years, by the year of birth
	Breast cancer	Ovarian cancer	Breast cancer	Ovarian cancer	Breast cancer	Ovarian cancer
<1920	46	33	39	11	4.5	1.0
1920–1929	51	36	44	11	5.2	1.1
1930–1939	55	36	47	12	5.9	1.1
1940–1949	58	34	50	11	6.4	1.1
1950+	59	34	51	11	6.5	1.1
Polygenic modifying variance: σp 2(t)=σm 2(t)=α+βt
	α̂=4.83 (95% Cl: 1.8–7.9)			=−0.06 (95% Cl: −0.12 to 0.00)

NA=not available.

Polygenic/modifying variance is a linear function of age, and the log BRCA1 and BRCA2 relative hazards are piecewise linear functions of age.