Calcium channel blockers and myocardial infarction: a case--control study in a Japanese hospital.
OBJECTIVE
To examine the relationship of the use of calcium channel blockers (CCBs) in hypertensive patients to myocardial infarction in Japan, where CCBs are prescribed much more frequently than in Europe and America.


METHODS
We conducted a nested case-control study using a hospital information system in Japan.


METHODS
Cases were hypertensive patients who were repeat visitors to Tokyo University Hospital as of April 1996 and had an incidence of fatal or non-fatal myocardial infarction between 1996 and 1999. Controls were hypertensive patients individually matched to cases by sex, age and history of angina pectoris.


RESULTS
The study consisted of 16 cases, who were matched to 80 controls. Of the 80 control patients, 54 (68%) received CCBs. On the other hand, all but one of 16 cases received CCBs and the crude odds ratio of myocardial infarction associated with the use of calcium channel blockers was as high as 7.0 (0.9-55.3). The odds ratio was reduced to 4.9 (0.6-42.4) when adjusted by diabetes and diastolic blood pressure.


CONCLUSIONS
Although the crude odds ratio of myocardial infarction associated with CCBs was high, the ratio was reduced when adjusted by known confounding factors, suggesting a mechanism of confounding by indication. In addition, the results obtained in this study using records from a single hospital should not be generalized.
Ohyama
Yoshiharu
Y
Department of Clinical Pharmacy, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo 192-0392, Japan.
Funao
Kazuhiro
K
Kawabe
Eri
E
Hayashi
Doubun
D
Yamazaki
Tsutomu
T
Iga
Tatsuji
T
Koide
Daisuke
D
Ohe
Kazuhiko
K
Kubota
Kiyoshi
K
D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000627:therapeutic use; D002121:Calcium Channel Blockers / Q000627:therapeutic use*; D016022:Case-Control Studies; D048909:Diabetes Complications; D005260:Female; D006751:Hospital Information Systems / Q000706:statistics & numerical data; D006785:Hospitals, University; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000188:drug therapy* / Q000453:epidemiology; D016017:Odds Ratio
D000959:Antihypertensive Agents; D002121:Calcium Channel Blockers