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Myocardial infarction and third generation oral contraceptives: aggregation of recent studies
Walter O Spitzer1, Janet M Faith, Kenneth D MacRae
1Emeritus Professor of Epidemiology, McGill University, Montreal, Canada.
Background:
Arterial cardiovascular and cerebrovascular adverse events associated with oral contraceptives (OC) are a major concern to the clinician. This paper aggregates the findings of seven recent oral contraceptive studies on the risk of acute myocardial infarction (MI) among users of second (2gen) and third (3gen) generation OC.
Methods:
Odds ratios (OR) from seven original studies published between 1996 and 2001 underwent meta-analysis. They had accrued 6464 subjects since 1996. In addition, estimates of 22 studies published from 1965 to 1966 were synthesized using medians and ranges as an historical point of reference.
Results:
Four meta-analyses were performed for each of the relevant comparisons. The point estimates for 3gen versus 2gen OC ranged from 0.44 (0.24-0.80) to 0.62 (0.38-0.99). Compared with non-users, the aggregated OR for 3gen OC was 1.13 (0.66-1.92); for 2gen OC it was 2.18 (1.62-2.94).
Conclusions:
This overview of seven controlled observational studies confirms that 3gen OC do not convey harm in regard to MI compared with non-users of OC. The aggregate data and the continuing replication of findings allow interpretation of benefit compared with older combined OC.