Table1. Characteristics of subjects with a single NTX measurement (single NTX) and subjects with repeated (2 or more) bone lead measurements (repeat bone lead).

	Single NTX (N=610)	Repeat bone lead (subject number=746, observation number=1377)*
Age (years), Mean (sd)	67.7 (7.5)	Mean (sd)	69.2 (7.4)
Current smoking status, % yes	7.0	% yes	5.9
Daily alcohol intake (gm/day), Mean (sd)	12.8 (18.0)	Mean (sd)	12.8 (18.3)
Number of years' Edu. Mean (sd)	14.2 (2.7)	Mean (sd)	14.3 (2.6)
NTx (nM BCE/mM creatinine), Mean (sd)	53.7 (68.7)		N.A.
Tibia lead (μg/g), Mean (sd)	21.9 (13.4)	Mean (sd)	21.3 (13.9), 19 (14)
Patella lead (μg/g), Mean (sd)	31.8 (19.2)	Mean (sd), Median (iqr)	29.9 (20.1), 26 (20)
Blood lead (μg/dL), Mean (sd)	5.9 (3.7)	Mean (sd), Median (iqr)	5.4 (3.4), 5.0 (4)

^*values are based on the 1377 observations