Table 2 Relations between sleep disorders and possible confounding factors, and with possible explanatory factors.

Symptom	Possible confounding factors				Possible explanatory factors
	Mean age (y)	Social class (% manual)	Smoking (% current)	Mean alcohol intake (cc/week)	Mean BMI (kg/m2)	Mean neck circumference (cm)
Insomnia
No	61.9	64	33	142	26.7	38.9
Yes	61.3	76	37	133	27.2	39.3
	p = 0.072	p<0.001	p = 0.256	p = 0.514	p = 0.063	p = 0.075
Restless legs
No	61.8	62	33	140	26.6	38.8
Yes	61.6	77	37	142	27.5	39.5
	p = 0.154	p<0.001	p = 0.097	p = 0.840	p<0.001	p<0.001
Snoring
No	62.0	65	33	141	26.4	38.7
Yes	61.3	65	35	137	27.5	39.4
	p<0.001	p = 0.986	p = 0.570	p = 0.646	p<0.001	p<0.001
Sleep apnoea
No	61.9	63	33	141	26.6	38.8
Yes	61.4	72	39	139	27.4	39.4
	p = 0.072	p = 0.002	p = 0.028	p = 0.862	p<0.001	p<0.001
Daytime sleepiness
No	61.8	61	32	147	26.6	38.8
Yes	61.7	73	38	127	27.1	39.2
	p = 0.437	p<0.001	p = 0.004	p = 0.026	p = 0.003	p = 0.002