Monday 29 November 1999 - 4pm, Room 122, Pearson Building
Department of Statistical Science - University College London
Speaker : Andrew Copas (UCL)
Title : Incorporating Retrospective Data into an Analysis of Time to Illness
Abstract: For studies of time to illness, the prospective cohort study is,
in general, the method of choice. When the time of origin is known for all
subjects, then a prevalent cohort study in which individuals are recruited
at variable times after the start of the illness process is a suitable
alternative. Often, when a prevalent cohort is being formed, data may also
be available on individuals who are already ill but are alive. The
incorporation of such data, which is practically appealing to many
researchers, is discussed. The nature of the required assumptions and the
need to also model the illness to death process are illustrated. Full
likelihood and pseudolikelihood techniques are outlined and compared with
each other and with the use of only prevalent cohort data in a small
simulation study. Two examples are discussed for illustration. The full
likelihood method is seen to be too complex for general application. The
use of pseudolikelihoods is easier to implement. If there is reliable
information on initiating event times and recruitment strategies are well
defined, then the incorporation of retrospective data may be beneficial. In
other situations, their incorporation is too problematic to be recommended.
Useful Web sites:
The programme of our statistical seminars is available at:
http://www.ucl.ac.uk/Stats/research/journals.html
Map with instructions on how to get to our department:
http://www.ucl.ac.uk/Stats/map.html
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K. Skouras, Lecturer in Statistics, Department of Statistical Science,
University College London, Gower Street, London WC1E 6BT, United Kingdom.
Tel: 0171-4193652 Fax: 0171-7383 4703
e-mail: [log in to unmask]
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