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 |
|---|---|---|---|---|---|---|---|
| Deceased | 22 | 33 | 51 | 59 | 80 | 104 | 126 |
| Frailty (e.g. intellectual disability) | 3 | 9 | 12 | 15 | 16 | 16 | 16 |
| Withdrawn | 230 | 518 | 800 | 951 | 1156 | 1435 | 1670 |
| Total ineligible | 255 | 560 | 863 | 1025 | 1252 | 1555 | 1812 |
| Contacted but did not return survey | 1332 | 653 | 1371 | 1994 | 1455 | 1399 | 1268 |
| Unable to contact participant | 2972 | 3953 | 2868 | 3029 | 3531 | 4107 | 4046 |
| Total non-respondents | 4304 | 4606 | 4229 | 5023 | 4986 | 5506 | 5314 |
| Respondents completed survey | 9688 | 9081 | 9145 | 8199 | 8009 | 7186 | 7121 |
| Eligible at current survey | 13992 | 13687 | 13384 | 13222 | 12995 | 12692 | 12435 |
| Response rate as % eligible | 69.2% | 66.3% | 68.3% | 62.0% | 61.6% | 56.6% | 57.3% |