Mortality and causes of death among Japanese diabetics in the Tokyo area: prospective follow-up study over four years.

Abstract

To clarify the mortality and causes of death among Japanese diabetics, we started a prospective follow-up study of 1,629 diabetics who had been registered at our Diabetes Center in 1976. After registration, all patients were checked annually for four years and we confirmed that they were still alive by sending questionnaires or obtaining copies of their resident cards. After a four-year follow-up, only 3 had dropped out, 1,486 were alive and 140 had died. The follow-up rate therefore was 99.8%. We obtained copies of the death certificates of all the deceased. It was shown that risk factors increasing the mortality ratio (the ratio of observed deaths to expected deaths) among Japanese diabetics were early onset of diabetes (0-29 years of age), treatment by insulin and the presence of diabetic retinopathy combined with proteinuria at registration. The most frequent cause of death among the 140 deceased cases was malignant neoplasm, the second ischemic heart disease and the third was cerebrovascular disease. Analysis of the underlying causes of death showed a significant increase in the death rate due to diabetes mellitus and ischemic heart disease among Japanese diabetics compared with the general population matched for sex and age.