Prevalence and prediction of silent ischaemia in diabetes mellitus: a population-based study

The aim of the study was to estimate the prevalence of silent ischaemia in diabetic subjects in the population, to compare the prevalence of silent ischaemia in diabetics and non-diabetics and to attempt to predict the presence of silent ischaemia in diabetic subjects.

A random sample of 120 users of insulin and 120 users of oral hypoglycaemic agents aged 40-75 years living in the Danish municipality of Horsens were asked to participate in the study. Corresponding to the youngest half of the sample two non-diabetic controls were randomly selected from the Central Population Register. ST-depression of horizontal or descending character of at least 0.1 mV measured 80 ms after the J-point on either exercise ECG or Holter ECG was considered indicative of myocardial ischaemia. Angina pectoris was considered present if the Rose questionnaire was positive, or chest pain was registered simultaneously with ECG evidence of ischaemia. Individuals with ischaemia, but without angina pectoris, were defined as persons with silent ischaemia.

Seventy-four percent of the invited group were included. The observed prevalence of silent ischaemia in diabetics was 13.5% (95% CI = 8.5-19.8%). No association was found between silent ischaemia and gender (P = 0.83) or diabetes type (P = 0.67). In the group of diabetics who had controls, the prevalence was 11.4%, and among the controls the prevalence was 6.4% (OR = 1.87, one-sided P = 0.079). Systolic blood pressure was highly predictive of silent ischaemia in the diabetic subjects (P = 0.005). No predictive value could be shown for other variables.

This is the first population-based study of silent ischaemia in diabetes. The prevalence of silent ischaemia in diabetic subjects was 13.5%. The frequency of silent ischaemia did not differ significantly between diabetics and non-diabetics. Systolic blood pressure was predictive of silent ischaemia in diabetes.