Table 1.

Baseline characteristics of the study population and the “complete study sample”

Characteristics (potential prognostic factors) *	Category	Study population (n=680)			Complete study sample ** (n=569)
		Freq. a (n)	% b	Miss. c (n)	Freq. a (n)	% b
Socio-demographics
Age, mean (SD)		39	(15)		39	(15)
Sex	Females	471	69.3		403	70.8
Marital status	Single	215	31.6		188	33.0
	Married	381	56.0		315	55.4
	Widowed	21	3.1		18	3.2
	Separated/Divorced	63	9.3		48	8.4
Education	< Grade 8	33	4.9	1	28	4.9
	Grade 8	97	14.3		76	13.4
	High school	173	25.4		148	26.0
	Post-secondary school	189	27.8		165	29.0
	Technical school	102	15.0		83	14.6
	University	85	12.5		69	12.1
Work statusd	Working	537	79.0		452	79.4
Collision, symptoms, comorbidity and health care
No. of days to reporting the collision, mean (SD)		16	(10)		16	(9)
Neck pain intensitye	No pain	0	0		0	0
	Mild	91	13.4	12	85	14.9
	Moderate	300	44.1		260	45.7
	Severe	277	40.7		224	39.4
Low back pain intensitye	No pain	295	43.4	12	259	45.5
	Mild	79	11.6		66	11.6
	Moderate	171	25.2		143	25.1
	Severe	123	18.1		101	17.8
Headache intensitye	No pain	116	17.1	3	105	18.4
	Mild	101	14.9		82	14.4
	Moderate	233	34.3		201	35.3
	Severe	227	33.4		181	31.8
Pain other than neck and back pain	Yes	529	77.8		432	75.9
Symptoms in arms or handsf	Yes	293	43.1		235	41.3
Pain when moving neck	Yes	593	87.2		494	86.8
Reduced neck movement	Yes	525	77.2		437	76.8
Sleeping problems	Yes	470	69.1		396	69.6
Musculoskeletal problem before collisiong	Absent	459	67.5	3	384	67.5
	No/Mild	140	20.6		125	22.0
	Severe	78	11.5		60	10.5
Headache before collisionh	Absent	412	60.6	1	345	60.6
	No/Mild	180	26.5		154	27.0
	Severe	87	12.8		70	12.4
Restrictions in daily home activity	Yes	411	60.4		342	60.1
Restrictions in leisure activityi	Yes	114	16.8		99	17.4
MD visits since collisionj	1	285	41.9	5	251	44.1
	2	238	35.0		192	33.7
	≥ 3	152	22.4		126	22.1
PT visits since collisionk	1	246	36.2	10	198	34.8
	2	189	27.8		164	28.8
	≥ 3	235	34.6		207	36.4
General health and psychology
Recovery expectationsl	Better soon	142	20.9	1	130	22.9
	Better slowly/Never better	320	47.1		267	46.9
	Don′t know	217	31.9		172	30.2
Current general healthm	Excellent	17	2.5		15	2.6
	Very good	54	7.9		49	8.6
	Good	190	27.9		164	28.8
	Fair	288	42.4		241	42.4
	Poor	131	19.3		100	17.6
General health the month before collisionn	Excellent	255	37.5		214	37.6
	Very good	250	36.8		218	38.3
	Good	130	19.1		100	17.6
	Fair/Poor	45	6.6		37	6.5
Anxiety or worry	Yes	285	41.9		238	41.8
Depressed moodo	Yes	300	44.7	18	255	44.8

^*Note: All characteristics (potential prognostic factors) concerned problems that participants experienced as a result of the injury unless otherwise stated.

^** Sample without patients who was lost to follow-up (n=81) and/or had missing data on potential prognostic factors (n=47).

^a No. of subjects in the category unless otherwise stated.

^b Percent unless otherwise stated.

^c No. of missing answer for the potential prognostic factor.

^d Work status: Not working; unemployed, disability leave, maternity leave, retired, homemaker, Working; fulltime, part time and student.

^e 11 point numeric rating scale (NRS) were 0 = no pain at all and 10 = pain as bad as it could be. Mild: 1-4, Moderate: 5-7, Severe: 8-10.

^f Feeling of numbness, tingling or pain in arms or hands.

^g The effect on health from muscle, bone or joint problems within 6 months before the collision.

^h The effect on health from headache within 6 months before the collision.

ⁱ Activities not related to home, work or education.

^j MD: Medical doctor.

^k PT: Physical therapist.

^l The answer to the “question”: “Do you think that your injury will…”.

^m The answer to the question: “In general, how would you say your health is now?”.

ⁿ The answer to the question: “How was your health the month before the collision?”.

^o Based on the Center for Epidemiologic Studies Depressive scale (CED-S) indicating depressed mood the past week: Yes = depressed mood (CED-S ≥16).