Morbidity of myocardial infarction multicenter study in Japan (3M study) - Study design and event rates for myocardial infarction and coronary death by age category in Japanese workers

Background Although there have been regional studies, there has not been a detailed nationwide investigation of the morbidity from acute myocardial infarction (MI) in Japanese workers. Methods and Results Registration of MI and sudden death was done by full-time occupational physicians in Japan. Among 133,099 workers (109,550 men, 23,549 women) from 41 workplaces (April 1994 to March 1997) and 257,440 workers (207,310 men, 50,130 women) from 76 workplaces (April 1997 to March 2000), 297 fatal and nonfatal cardiac events were registered. The definitions of MI and coronary death followed the criteria of the WHO MONICA Project. The event rate in men rose sharply around the age of 45years. Using definition I (fatal definite+fatal possible+fatal unclassifiable+ nonfatal definite), the age-standardized annual event rate and case fatality rate for men aged 35-64 years was 40.2 per 100,000 persons and 22.2%, respectively. These figures were significantly lower compared with those from Western reports and were also lower than previously reported for Japanese communities. Conclusion The Morbidity of Myocardial Infarction Multicenter Study in Japan revealed a surprisingly low incidence of coronary events, which may be attributable to prevention and early treatment of coronary risk factors among company workers in Japan.