Table 2.

Relationships between baseline characteristics, sleep duration, and insomnia

Baseline characteristics	Sleep duration in hours				P value	Mean insomnia score (mean (s.d.))	P value
	≤5	6	7–8	≥9
n (%)	363 (7.4)	946 (19.3)	3,240 (66.0)	364 (7.4)
Age in years
32–39	16	22	23	19	<0.0001	6.06 (2.3)	<0.0001
40–49	28	35	33	22		6.54 (2.4)
50–59	25	22	22	15		7.15 (2.5)
60–69	14	12	12	14		7.23 (2.7)
70–79	13	7	8	20		7.43 (2.8)
80–86	4	3	3	11		7.62 (2.8)
Sex
Women	64	62	64	63	0.5409	6.98 (2.6)	<0.0001
Men	36	38	36	37		6.39 (2.4)
Race/ethnicity
Caucasian	87	90	93	88	<0.0001	6.84 (2.5)	<0.0001
Non-Caucasian	13	10	7	12		6.05 (2.7)
Education
>High school graduate	43	29	26	44	<0.0001	7.08 (2.8)	<0.0001
High school graduate	57	71	74	56		6.64 (2.4)
Body weight
Underweight (BMI ≤18.5)	4	3	3	7	<0.0001	7.06 (2.6)	0.3701
Normal weight (BMI >18.5 and <25)	42	47	53	48		6.79 (2.5)
Overweight (BMI ≥25 and <30)	37	35	32	34		6.72 (2.5)
Obese (BMI ≥30)	17	15	12	11		6.75 (2.6)
Diabetes at baseline
Yes	6	3	3	4	0.0086	7.79 (3.1)	<0.0001
No	94	97	97	96		6.74 (2.5)
Alcohol abstinent
Yes	42	32	33	47	<0.0001	6.88 (2.8)	0.0320
No	58	68	67	53		6.72 (2.4)
Cigarettes per day
= 0	65	66	70	74	0.0141	6.87 (2.5)	0.0001
>0 and <20	12	10	11	8		6.56 (2.6)
≥20	2	24	19	18		6.53 (2.5)
Physical activity
2-Low	15	7	8	16	<0.0001	7.57 (2.9)	<0.0001
3	19	17	18	19		7.03 (2.5)
4	34	43	44	41		6.78 (2.4)
5	21	20	20	18		6.45 (2.4)
6-High	11	13	11	6		6.22 (2.5)

BMI, body mass index.