A defining feature of the ALSPAC data set is the breadth of repeat measures taken at frequent intervals across the life course. Loss to follow-up caused by permanent attrition to the study (Figure 6) reduces the proportion of the sample who are eligible for follow-up at each time point. In addition, the fluctuations in response described previously decreases the participating sample that consistently responds (Figure 7). While these factors impact on the availability of repeat measures across all time points, a core sub-sample of over 3000 families have responded to all the 55 assessments open to the ‘full’ sample (defined in the footnotes to Figure 7) and 5777 have responded to 75% or more of these assessments (≥41 individual assessments).
