A major strength of the study was the ability to include
more than a million woman years of observation, accumulated
over a 39 year period and involving nearly
three times as many deaths (a total of more than
4600) as before.4 A previous study has shown good
agreement between the cause of death reported by
the general practitioners and that on the death
certificate.7 Although both sources of information are
prone to error in the attribution of underlying cause of
death, we have no reason to suspect systematic differences
because of a woman’s use (or not) of oral contraception.
This is especially so for more recent events, for