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Table 1
Mobile phone variables at baseline
Category	Mobile phone variables	Men		Women
		n = 1455		n = 2701
		Freq	%	Freq	%

	Frequency of calls
Low	0 per day	69	5	51	2
Low	1-5 per day	952	65	1946	72
Med	6-10 per day	301	21	543	20
High	11-20 per day	97	7	108	4
High	More than 20 per day	36	2	47	2
	Frequency of SMS messages
Low	0 per day	126	9	58	2
Low	1-5 per day	906	62	1609	60
Med	6-10 per day	262	18	634	23
High	11-20 per day	98	7	259	10
High	More than 20 per day	60	4	140	5
	Mobile phone use
Low	Low Calls + Low SMS	804	55	1433	53
Med	Low Calls + Med SMS or vice versa	326	22	616	23
High	High Calls and/or High SMS, or Med Calls + Med SMS	323	22	645	24
	Awakened at night
Low	Never	600	41	989	37
Med	Only occasionally	657	45	1248	46
High	A few times per month	164	11	386	14
High	A few times per week	27	2	68	3
High	Almost every day	6	0	9	0
	Availability demands
Low	Never	23	2	12	0
Low	Now and then, but not daily	82	6	86	3
Low	Daily, but not all day	278	19	828	31
Med	All day	680	47	1127	42
High	Around the clock	388	27	642	24
	Accessibility stress
Low	Not at all stressful	892	61	1229	46
Med	A little bit stressful	418	29	1083	40
High	Rather stressful	115	8	311	12
High	Very stressful	28	2	75	3
	Overuse
	Item 1: Use too much	184	13	587	22
	Item 2: Tried to cut down unsuccessfully	87	6	371	14
Low	No item	1199	84	1898	71
Med	One item	183	13	579	22
High	Both items	41	3	187	7

Frequencies (Freq) and percentages (%) in mobile phone variables for the men and women, including categorizations into Low, Medium (Med), and High. Questionnaire items are presented in footnote¹. Missing values (non-responses to items) are not accounted for, which means that the n varies for the variables. ¹Questionnaire items; Frequency of calls: How many mobile phone calls on average have you made and received per day (the past 30 days)?, Frequency of SMS messages: How many SMS messages on average have you sent and received per day (the past 30 days)?, Awakened at night: How often have you been awakened by the mobile phone at night (the past 30 days)?, Availability demands: To what extent are you expected by those around you to be accessible via the mobile phone?, Accessibility stress: To what extent do you perceive accessibility via mobile phones as stressful?, Overuse: 1. Do you or someone close to you think that you use the mobile phone too much?, 2. Have you tried, but failed, to cut down on your use of the mobile phone?
Thomée et al. BMC Public Health 2011 11:66 doi:10.1186/1471-2458-11-66

Table 1