Tracing 8,600 participants 36 years after recruitment at age seven for the Tasmanian Asthma Study

Objective: To trace all participants 36 years after the original Tasmanian Asthma Study (TAS). Methods: In 1968, the TAS investigated as thma in 8,583 children who were born in 1961. We attempted to trace these participants in 2002-04 using names, dates of birth and gender. Current addresses were sought by computer linkage to the Commonwealth Electoral Roll, the Medicare database and the Tasmanian marriage records. Computer linkage was conducted with the National Death Index (NDI). Siblings of participants were also linked to the Commonwealth Electoral Roll and those identified were sent a letter requesting the participant's address. The Australian Twin Registry (ATR) and the 1991-93 TAS substudy were used to locate participant addresses. Results: After three rounds of electoral roll linkage, 56% of all cohort members were traced. Name changes were identified for 49% of the 3,477 females not initially matched to the electoral roll using linkage to marriage records. NDI linkage yielded a 0.7% match. Medicare linkage identified addresses for 27% of the 1,982 remaining participants. Writing to siblings located 60% of 1,661 participants. One hundred and eighty-three participants were matched to the 1991-93 TAS and 23 twins matched to the ATR. Overall, 81.5% of the cohort members were identified. Conclusions: With these methods, we have been able to trace a possible address for a large portion of the original participants, with the electoral roll linkage being the most useful. Implications: It is possible to trace Australians for follow-up studies using electronic linkage, although without unique identifiers it is labour and resource intensive and requires matching to several databases.