'Alive' searches as complementing death searches in the epidemiological follow-up of Ontario miners

'Alive' searches have been used to complement the 'death' searches, in a study of the mortality experience of a cohort of Ontario miners. The purpose has been to develop a way of distinguishing between those cohort members who are 'confirmed' alive at a given time, and those who are 'lost to follow-up'. A total of 30,000 Workers' Compensation Board (WCB) records with valid Social Insurance Numbers (SIN) were used to search the income tax files by computer over two consecutive years (1977 and 1978) representing nearly 27 million tax returns. These tax file searches using SIN numbers have provided information on the procedures to be used in, and likely success of, the corresponding searches of the tax files that could be carried out where the SIN number is not available on the work records. The latter kind of search would have to be based on names, birth dates and such, and would be probabilistic in nature. The results of the study were as follows: After the initial death search, it was found that 7.5% of the cohort had died in Canada and their records were found on the Mortality Data Base. The remaining 92.5% has been 'assumed alive' in the earlier analysis. After the 'alive' follow-up using the income tax file, one was able to confirm that 89.1% of the 'assumed alive' had filed an income tax after the study period. Thus only 3.4% of the cohort remained untraced. Among those there could be an admixture of deaths outside of Canada, persons who have moved outside of Canada and are still alive, and/or persons alive within Canada, but who have not filed an income tax return. This study has indicated that the procedures developed are useful for purposes of 'alive' follow-up, for evaluation of the quality of the Mortality Data Base-cohort death file searches, for improving the accuracy of analytical results of epidemiological studies, and for reducing the cost and labour of resolving doubtful death searches