Benefits of extensive recruitment effort persist during follow-ups and are consistent across age group and survey method. The TRAILS study

Table 1 Characteristics of the sample at the four measurements waves of TRAILS

^a Of the 2,935 eligible children asked to participate at T1.
^b Of the 2,230 included children at T1.
^c Non-responders at T3 include 2 deceased, 7 who were physically or psychologically unable to participate, 4 who were detained or moved abroad, and 31 untraceable or unreachable participants. Other non-responders refused participation or did not return any information (n = 372).
^d Non-responders at T4 include 5 deceased, 3 who were physically or psychologically unable to participate, and 1 detained participant, 16 untraceable and 43 unreachable participants, and 9 participants who moved abroad. Other non-responders refused participation or did not return any information (n = 272).