Table 1. General characteristic of the two-stage GWAS study subjects.

Characteristic	First stage	Second stage	P valuea , b
N	1999	1496
Age (years)	37.54±11.10	37.31±10.80	0.54
Smoking
Yes	1015 (50.8)	771 (51.5)	0.66
No	984 (49.2)	725 (48.5)
Body mass index (kg.m−2)	23.31±3.44	23.46±3.34	0.18

^at-Test was used to compare means between the first and the second stages.

^bChi-square test was used to compare the differences in categorized variables.