That is, persons
were excluded if they had diabetes at any time from the date of
TZD introduction onwards but had a period of diabetes of
1 year or more when their drug data were not captured. In
practice, this means that all TZD users in the analysis were
incident or very recent users. If diabetes ascertainment was
unclear, then at least 1 year of diabetes from the presumed date
of onset without being on any glucose-lowering drugs had to
have elapsed to be considered evaluable for subsequent cumulative
exposure to TZD or other drugs. This condition was set
to limit these study entrants to probable cases of incident
diabetes. For models in which we further adjusted for other
glucose-lowering drugs, anyone whose cumulative exposure
to those drugs could not be evaluated was excluded. In practice,
this means that anyone with diabetes preceding the availability
of their drug data by 1 year or more was excluded from
these models, but those with retrospective data or drug exposure
throughout their diabetes were included.