Ochi, James W.

In a population-based investigation among the residents of Rochester, Minnesota, the diabetes mortality rate was 8.5 per 100,000 person-years with diabetes as the underlying cause of death, 31.5 per 100,000 person-years with diabetes as an underlying or contributory cause, and 82.7 per 100,000 person-years if all deaths among diabetic individuals were counted. Diabetes was not mentioned on the certificate in 62% of the 428 diabetic deaths during 1965–1974. When the clinical characteristics of the subgroup of mortality cases in 1969 were compared with those of the prevalence cases on 1 January 1970, it was found that mortality cases tended to be older, were more often on insulin therapy, and were more likely to have macro- and microvascular complications. Because mortality data are sometimes used to infer trends and characteristics for the diabetic population at large, it is important to recognize these biases.

Of all the known diabetic individuals residing in the community of Rochester, Minnesota, only about one-half would have been recognized through a review of the medical records of 1 yr. Only one-fifth of the diabetic residents were hospitalized during the index year and a similarly small proportion were attended in a diabetes clinic. This selective process produced distortion in the apparent clinical spectrum of diabetes observed at different levels in the medical care system. Notable was overestimation of the relative importance of insulin-dependent diabetes and of the vascular complications of diabetes among hospital and diabetes clinic patients. Referral bias should be taken into account when differences are noted in the epidemiologic features of diabetes as reported from different types of medical care settings.

In a population-based study in Rochester, Minnesota, the clinical characteristics of 1135 patients newly diagnosed with diabetes (1945–69) were compared with those of 810 residents with diabetes mellitus on prevalence day (1 January 1970). The prevalence patients were older and the male:female ratio was reduced from that seen among incidence cases. The prevalence patients were more likely to be on oral agents, had lower fasting blood glucose levels, were less likely to be symptomatic, but were more likely to have macrovascular and microvascular complications. These differences seemed to come about as a result of variation in survival rates among patients with specific characteristics, differential migration of certain groups of patients, and changes in the status of individuals.