Characteristics of the pre-clinical state in type 11 diabetes mellitus - abstract

ABSTRACT

Preclinical type II diabetes was recognized by the U.S. National Diabetes Data Group and the World Health Organization in 1979 - 80. Their recognition of this condition was based on studies of people with varying degrees of post-challenging glucose tolerance who were followed prospectively for the development of complications of diabetes mellitus, primarily retinopathy. It was found that undiagnosed diabetic subjects whose 2-hour post-challenge glucose value was o11.1 mmol/l were at high-risk of developing diabetic complications. Subsequent studies have found that undiagnosed pre-clinical type II diabetes mellitus is very common in many countries. In the US population, it is found in 10 - 20 percent of persons aged 50 years and older, with even higher rates in Blacks, Mexican Americans, and American Indians. This is a significant proportion of the American population to have a disease that conveys increased morbidity and mortality and yet is totally untreated. There is significant fasting (Mean 7.5 mm01/1) and post-challenge (mean 14.4 - 15.0mm01/1) hyperglycaemia among subjects with preclinical type II diabetes mellitus in the USA. The levels of hyperglycaemia are not benign. Indeed, if patients with known diagnosed diabetes mellitus exhibited these values, their hyperglycaemia would surely not remain untreated. Certainly, at least dietary therapy would be instituted, if not oral hypoglycaemic agents. Nevertheless, all subjects with pre-clinical type II diabetes are undiagnosed and their hyperglycaemia remains untreated. When in the natural history of diabetes mellitus is type II diabetes diagnosed? Recent data show that retinopathy begins developing at least 7 years before clinical diagnosis of type II diabetes mellitus and that onset of type II diabetes mellitus probably occurs at least 5 years before that. During this entire 12-years period, hyperglycaemia in these undiagnosed cases is totally untreated and significant retinopathy is developing, indicating that widespread structural lesions related to diabetes mellitus are occurring. Other data confirm that pre-clinical type II diabetes mellitus is not a benign condition. Significant complications are present in patients at diagnosis. For example, 21 percent of newly diagnosed patients have retinopathy in US studies and prevalence of retinopathy was 29 percent among newly diagnosed patients enrolled in the UK Prospective Study of Type II diabetes mellitus. Prevalence of macrovascular disease in undiagnosed NIDDM is about equal to that found in diagnosed diabetes mellitus, and rates of coronary heart disease in both diagnosed and undiagnosed diabetes mellitus are about twice the rate found in non-diabetics. Mortality in undiagnosed diabetes mellitus is also equal to that of diagnosed and both are significantly higher than that in non-diabetics. Risk factors for micro- and Macro-vascular complications in pre-clinical Type II diabetes mellitus are very common and are as frequent as those found in diagnosed diabetics. The prevalence of treatable risk factors for subjects with undiagnosed diabetes mellitus in the U.S.A. includes 31 percent exceeding fasting plasma glucose of 7.8 mmol/l. Obesity is present in 67 percent, including 82 percent of women and 50 percent of men. Over 60 percent have hypertension, only half of which is controlled. Total cholesterol>240mg/dl is found in 49 percent and LDL-cholesterol > 160 mg/dl is found in 42 percent. Prevalence of hypertriglyceridaemia is 28 percent and 32 percent smoke cigarettes. Dietary fat intake>30 percent of calories occurs in 79 percent of subjects with undiagnosed diabetes mellitus, saturated fat>10 percent of calories occurs in 77 percent, and subjects with pre-clinical diabetes mellitus are thus at high risk for coronary heart disease. We have methods in our therapeutic armamentarium to deal with all of these risk factors, should we choose to find and diagnose the millions of people who have undiagnosed diabetes mellitus(AU)