Table 7.

Data from the epidemiologic literature on back pain in boys and girls (age included)

	Petersen et al. [ 19 ]	Grøholt et al. [ 26 ]	Sato et al. [ 22 ]	Stanford et al. [ 20 ]	Kjær et al. [ 7 ]
Country	Sweden	Nordic countries	Japan	Canada	Denmark
Design	Cross sectional	Cross sectional	Cross sectional	Longitudinal – 8 yrs	Cross sectional + follow up
Study sample	Randomized cluster sample of pupils	Population registries children survey	Elementary and junior high school-children in Niigata City	Non-institutionalized civilian population (1994–5, 1996–7, 1998–9, 2002–3)	Primary/secondary school. 38 state schools in one municipality
Response rate	97%	64.5-69%	79.8%	?	62%, 57%, 58%
Valid sample size	1121	5911 (BP)	34423	2488	479, 439, 443
Data collection	Questionnaire	Questionnaire	Questionnaire	Computer ass. Interview + Questionnaire	Interview + Questionnaire
Age group	6-13	7-9, 10–12, 13–15, 16-17	9-15	10-18	9, 13, 15 (mean 9.7, 13.1, 15.7)
Definition of back pain	Backache the last 6 months	Has the child had any of the following complaints? (BP, headache e.g.)	Any LBP now	Backache past 6 months	Any spinal pain
Gender	No gender difference	Girls > boys in all pain categories	11-12y girls > boys	Girls > boys	No difference in overall back (spinal) pain reporting at age 9 and 13 yrs.
Age (prevalence increase)	Prevalence of bachache higher from grades 4–6 than in grades 0–3 (Method change)	BP + headache most prevalent in the oldest age groups compared to the youngest	Increasing prevalence with grade levels until age 14 (LBP: Point prevalence)	Girls 12–18 yrs > boys 12–18 yrs	> 13 yrs