Table 3. Relationship between normal cranial bone marrow typing and age at an altitude >4,100 m.

Age group (years)	Bone marrow type, n (%)						Diploe thickness (mm)
	Ia	Ib	II	IIIa	IIIb	IV
0–5	21 (42.0)	22 (44.0)	7 (14.0)	0 (0.0)	0 (0.0)	0 (0.0)	1.80±0.59
6–14	5 (7.1)	16 (22.9)	33 (47.1)	4 (5.7)	12 (17.1)	0 (0.0)	2.79±0.85
15–29	0 (0.0)	0 (0.0)	13 (18.6)	9 (12.9)	44 (62.9)	4 (5.7)	3.67±0.87
30–49	0 (0.0)	0 (0.0)	9 (12.9)	8 (11.4)	47 (67.1)	6 (8.6)	3.68±1.00
≥50	0 (0.0)	0 (0.0)	3 (6.0)	6 (12.0)	15 (30.0)	26 (52.0)	4.32±0.90
χ2/F (P)	335.266 (0.000)						67.750 (0.000)
r (P)	0.758 (0.000)						0.646 (0.000)