TABLE 1.

Demographic and clinical characteristics of medical students.

Predictors	Total	Training set	Validation set	P
	(N = 5,140)	(N = 3,855)	(N = 1,285)
Sleep quality
Good	3,502 (68.1%)	2,608	894	0.210
Poor	1,638 (31.9%)	1,247	391
Gender
Men	1,826 (35.5%)	1,378	448	0.590
Women	3,314 (64.5%)	2,477	837
Age (years)				0.720
<18	44 (0.9%)	33	11
18–21	3,587 (69.8%)	2,675	912
22–25	1,506 (29.3%)	1,142	364
>25	11 (0.2%)	9	2
Major
Clinical medicine	2,483 (48.3%)	1,869	614	0.970
Stomatology	496 (9.6%)	372	124
Traditional Chinese medicine	651 (12.7%)	485	166
Nursing	1,007 (19.6%)	754	253
Medical imaging	220 (4.3%)	160	60
Pharmacy	283 (5.5%)	215	68
Character self-assessment
Introverted	3,243 (63.1%)	2,444	799	0.450
Extrovert	1,897 (36.9%)	1,411	486
Smoking				0.110
Don’t smoking	4,798 (93.4%)	3,590	1,208
Currently smoking	237 (4.6%)	177	60
Quitting smoking	105 (2.0%)	88	17
Drinking				1.000
Don’t drinking	3,526 (68.6%)	2,644	882
Currently drinking	1,614 (31.4%)	1,211	403
Study stress
Very light	124 (2.4%)	92	32	0.190
Light	3,317 (64.5%)	2,457	860
Heavy	1,368 (26.6%)	1,053	315
Very heavy	331 (6.4%)	253	78
Feeling unwell
Yes	2,113 (41.1%)	1,586	527	0.960
No	3,027 (58.9%)	2,269	758