Table 4.

Model parameters estimated from variance partitioning of bone mineral density

Parameter	Spine BMD (×100)	Total hip BMD (×100)	Femoral neck BMD (×100)
μ	100.86	98.11	89.24
β(age)	−1.01	−1.35	−1.18
β(being post-menopausal)	−8.57	−14.31	−13.11
β(age* post-menopausal)	−0.41	3.40	2.08
β(age2)	0.01	0.01	0.01
β(age2* post-menopausal)	−0.003	−0.03	−0.02
β(height)	0.75	0.90	0.92
β(bmi)	0.84	1.34	1.18
σ G-post	12.61	10.78	9.19
σ G-pre	10.82	9.48	9.63
σ E-post	5.13	4.20	5.58
σ E-pre	1.34	[0]a	1.48
ρG	0.82	0.81	0.95
LL(full model)	−331.70	−247.07	−241.25
Hypothesis 1:	H0: genetic variance equal between pre-menopausal and post-menopausal women
	Parameterization: σG-pre = σG-post
LL (nested model):	−332.19	−247.58	−241.30
χ 2 1	0.98	1.02	0.09
P	0.32	0.31	0.76
Conclusion:	Accept H0	Accept H0	Accept H0
Hypothesis 2:	H0: environmental variance equal between pre-menopausal and post-menopausal women
	Parameterization: σE-pre = σE-post
LL (nested model):	−331.97	−247.87	−242.20
χ 2 1	0.54	1.60	1.90
P	0.46	0.20	0.17
Conclusion:	Accept H0	Accept H0	Accept H0
Hypothesis 3:	H0: genetic correlation similar between pre-menopausal and post-menopausal women
	Parameterization: ρG = 1
LL (nested model):	−332.43	−248.99	−241.36
χ 2 1	1.46	3.84	0.22
P *	0.11	0.025	0.32
Conclusion:	Accept H0	Reject H0	Accept H0

Model parameters: μ= mean BDM; β= regression coefficients (for age, age*sex, age2, age2*sex, height and body mass index); σ_G-pre = genetic SD in pre-menopausal women; σ_G-post= genetic SD in post-menopausal women; σ_E-pre= environmental SD in pre-menopausal women; σ_E-post= environmental SD in post-menopausal women; ρG= genetic correlation in BMD between pre-menopausal and postmenopausal women. LL log likelihood.

^aMaximum likelihood estimate converged at estimate at lower boundary.

^*P values for hypothesis 3 based on a 1/2:1/2 mixture of a χ²₁ and a point mass of zero