Prevalence and tracking of back pain from childhood to adolescence

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Published online 2011 May 16. doi: 10.1186/1471-2474-12-98

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Table 1

Summary of demographic and study data in a longitudinal study of Danish children/adolescents at three time points (T1, T2 and T3).

Description of studies
Time point	T1	T2	T3

Number of participants: males/females	227/252	250/234	192/251
Age mean [range]	9.7 [8.7,15.5]	13.1 [12.1 - 14.4]	15.7 [14.7 - 17.1]
Years since last interview [range]		3.4 [3.0 - 4.0]	2.7 [2.2 - 3.1]
Period of data collection	August 1997 -June 1998	March 2001 -October 2001	November 2003 -May 2004