Table 1

Descriptive characteristics of Shift Worker Study participants according to work shift status and gender

Covariate	Day shift				Night shift
	Female		Male		Female		Male
	N	%*	N	%†	N	%*	N	%†
Age group (years)‡
20–25	20	13	20	13	25	15	25	14
26–30	25	16	32	20	31	18	55	30
31–35	26	17	24	15	34	20	25	14
36–40	39	26	31	20	37	21	36	20
41–45	41	27	19	12	42	24	13	7
46–50	1	1	14	9	3	2	15	8
51–55	0	0	18	11	0	0	13	7
Body mass index (wt (kg)/ht (m)²)
<18	0	0	1	1	0	0	0	0
18–25	97	64	65	41	95	55	67	37
25–30	54	35	91	58	75	44	109	60
>30	1	1	1	1	2	1	6	3
Number of alcoholic beverages consumed§
0	109	72	113	71	125	73	112	61
1	24	16	17	11	17	10	17	9
2	12	8	15	9	10	6	17	9
3 or more	7	5	13	8	20	12	36	20
Tobacco use (any)§
Any	10	7	13	8	16	9	20	11
By type
Cigarettes	10	7	9	6	16	9	18	10
Patch	0	0	2	1	0	0	1	1
Medication use (any)§
Psychotherapeutics	20	13	14	9	16	9	8	4
Sedatives	2	1	1	1	1	1	4	2
β-blockers	2	1	0	0	3	2	3	2
Thyroid medications	11	7	0	0	11	6	1	1
Steroids	7	5	1	1	7	4	1	1

*Percent calculated from 152 female day shift participants and 172 female night shift participants with night-time sleep urine samples.
†Percent calculated from 158 male day shift participants and 182 male night shift participants with night-time sleep urine samples.
‡Calculated according to date of first urine collection.
§In the 24 h ending the night-time sleep period.