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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 pointT1T2T3

Number of participants: males/females227/252250/234192/251
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 collectionAugust 1997 -June 1998March 2001 -October 2001November 2003 -May 2004