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1973-78 cohort

Among the 1973-78 cohort, 69% responded to Survey 2 in 2000, 66% to Survey 3 in 2003, 68% responded to Survey 4 in 2006, 62% to Survey 5 in 2009 and to Survey 6 in 2012, and 57% to Survey 7 in 2015 (See Table below). This retention compares well with other surveys of this highly mobile age group. The major reason for non-response among the 1973-78 cohort has been that the research team has been unable to contact the women (between 21% and 28% of the cohort at subsequent surveys), despite using all possible methods of maintaining contact. Women in their twenties are characterised by high levels of mobility, change of surnames on marriage, often not having telephone listings, not being registered to vote, and making extended trips outside Australia for work, education, or recreation. Despite these losses, modelling has shown that there is no serious bias in estimates of associations between risk factors and health outcomes in longitudinal models (Powers, J., & Loxton, D. (2010). The Impact of Attrition in an 11-Year Prospective Longitudinal Study of Younger Women. Annals of Epidemiology, 20(4), 318-321).

Participation and retention of 14,247 women in the 1973-78 cohort of women who were 18-23 years old at the first survey in 1996

Year
Survey
Age in years
2000
Survey 2
22-27
2003
Survey 3
25-30
2006
Survey 4
28-33
2009
Survey 5
31-36
2012
Survey 6
34-39
2015
Survey 7
37-42
2018
Survey 8
40-45
Deceased2233515979103125
Frailty (e.g. intellectual disability)391215161616
Withdrawn230518800951115714361671
Total ineligible2555608631025125215551812
Contacted but did not return survey133265313711994145513991268
Unable to contact participant2972395328683029353141074046
Total non-respondents4304460642295023498655065314
Respondents completed survey9688908191458199800971867121
Eligible at current survey13992 136871338413222129951269212435
Response rate as % eligible69.2%66.3%68.3%62.0%61.6%56.6%57.3%
Data known as at 2nd July 2021