The importance of classifying initial co-morbidity in evaluating the outcome of diabetes mellitus

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Abstract

The associated co-morbid diseases present at the time of discovery of adult maturity-onset diabetes mellitus have not hitherto been quantitatively related to the subsequent course of the patients.

From existing medical records and other solicited data, complete 5-yr follow-up was obtained for an ‘inception cohort’ of 188 patients who were treated during the years 1959–1962 at the West Haven VA Hospital and whose diabetes was first diagnosed within 6 months before ‘zero time’, which was the date of discharge for the ailment that had provoked hospitalization. A special classification was developed for categorizing the zero-time co-morbidity of the patients as prognostically cogent or non-cogent, and for dividing cogent co-morbidity into vascular and nonvascular types, with functional severity graded as none, moderate, and severe.

The fatality rate at 5 yr after zero time was 40 per cent (76/188) for all patients, but distinctive gradients of fatality were noted for age, for type of co-morbidity, and particularly for severity of co-morbidity. The 5-yr fatality rate after zero time was 7 per cent in forty-one patients with no cogent co-morbidity, 33 per cent in seventynine patients with moderate co-morbidity and 69 per cent in sixty-eight patients with severe co-morbidity.

Of the sixty-eight patients with severe initial co-morbidity, 53 per cent later died of the same or a related ailment; in the seventy-nine patients with moderate co-morbidity, the analogous death rate was 13 per cent. Death was due to ‘vascular causes’ in 52 per cent of seventy-seven patients who initially had vascular co-morbidity, in 7 per cent of seventy patients with nonvascular co-morbidity, and in 2 per cent of forty-one patients with no cogent co-morbidity. Among 5-yr survivors, the occurrence rate of new vascular events (or ‘diabetic complications’) was directly related to the same features of age and co-morbidity that seemed to affect fatality.

These data indicate that the outcome of patients with maturity-onset diabetes mellitus depends on the type and functional severity of the co-morbid diseases present when the diabetes is detected. An appropriate analysis of co-morbidity, although omitted from existing statistical studies of diabetes, is pre-requisite to evaluating the results of different modes of therapy.

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From the Eastern Co-operative Studies Center and the Department of Medicine of the West Haven Veterans Administration Hospital, and the Departments of Medicine and Epidemiology of the Yale University School of Medicine. This investigation was supported in part by PHS Grant Number HS 00408 from the National Center for Health Services Research and Development and by a grant from the Upjohn Company.

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