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could also be reported as a nested case-control study with an historical comparison
group.
Advantages of case-control studies are described as being able to study rare
diseases with a relatively small sample size and are generally less expensive. The two
most commonly cited disadvantages of case-controlled studies however are described as
confounding and bias, that is, the difficulty in describing cause and effect ( confounding
variables) and bias, in particular recall bias with cases over reporting and cases under
reporting an exposure (Bombardier, Kerr, Shannon, & Frank, 1994). The case-
controlled design is appropriate for this study as childhood cancer is an uncommon
disease and it would have been difficult to recruit a large sample. Data had already been
collected from a normative control group that was current and provided a large
representative sample of the same source population i.e. New Zealand youth aged
between 12- 18 years. This large control group allowed for multivariate comparison
with child cancer survivors with allowance for differences between the groups, in age,
sex, ethnicity and socioeconomic status to control for those potentially confounding
variables.
3.4 Cases: Childhood Cancer Survivors
There are two primary cancer treatment centres (Auckland and Christchurch)
supported by a network of regional outreach services throughout New Zealand. These
provide supportive and follow-up care to patients domiciled outside the main treatment
centres. These links made it easier to identify and obtain current contact details for
prospective participants.
Inclusion criteria were all survivors of a childhood disease that met the
International Classification of Childhood Cancers version 3 (ICCD-3), aged between 12
years and 18 years inclusive at the commencement of the study and who were at least
two years from completion of therapy and disease free. Participants had to have English
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