Table 1.

Description of Studied Populations

	Discovery Cohort		Replication Cohorts
			First Step		Second Step
	Hong Kong Southern Chinese Discovery Cohort		Hong Kong Southern Chinese First-Step Replication Cohort		Hong Kong Osteoporosis Study Prospective Cohort			Northern Chinese Population
Group	High BMD	Low BMD	High BMD	Low BMD	BMD	Nonfracture	Fracture	BMD
Number	376	424	264 (168)	456 (124)	1881	1637	244	1584
Age (years)	46.6 ± 14.8	51.1 ± 15.9	48.3 ± 16.3	49.0 ± 16.0	62.3 ± 8.9	60.7 ± 8.2	67.4 ± 9.9	56.2 ± 11.3
Height (m)	1.58 ± 0.06	1.53 ± 0.07	1.65 ± 0.09	1.57 ± 0.08	1.52 ± 0.06	1.53 ± 0.06	1.50 ± 0.06	1.60 ± 0.06
Weight (kg)	61.1 ± 9.9	49.1 ± 6.7	67.1 ± 11.4	52.1 ± 9.5	55.4 ± 9.5	55.7 ± 9.5	54.1 ± 9.3	59.5 ± 9.4
BMD Z-Score
Lumbar Spine	1.05 ± 0.78	−1.59 ± 0.53	1.36 ± 0.89	−1.34 ± 0.72	−0.43 ± 1.18	−0.39 ± 1.18	−0.72 ± 1.17	−0.05 ± 1.24
Femoral Neck	1.15 ± 0.79	−1.36 ± 0.60	1.01 ± 0.84	−1.16 ± 0.69	−0.35 ± 0.97	−0.29 ± 0.97	−0.78 ± 0.93	0.71 ± 0.92

Data are expressed as mean ± standard deviation. The subject number is total number (the number of male subjects, if applicable, is given in parentheses) in each cohort. A total of 1520 subjects with extreme BMD phenotype were selected from a growing database of Hong Kong Southern Chinese (more than 7000 volunteers). The low BMD subjects are defined as an individual having BMD Z-score ≤ −1.28 at either lumbar spine (LS) or femoral neck (FN), which is equivalent to the lowest 10% of the total cohort, while high BMD subjects are individuals with BMD Z-score ≥ +1.0 at either of the two skeletal sites. First, a subset of 800 women was selected from the Hong Kong Southern Chinese (n = 1520) as the discovery cohort, and then the remainder of individuals (n = 720, 59.4% women) of the extreme population were used for the first-step replication.