Trong UKPDS nguy cơ của các biến chứng microvascular và macrovascular của bệnh tiểu đường type 2 được gắn liền với tăng đường huyết, đo bằng HbA1C. Không có bằng chứng của một ngưỡng và có ba tăng trên phạm vi 10% (Hình ). Mặc dù tất cả những nghiên cứu này chứng minh rõ ràng | 18 SECTION I MICRO- AND MACROVASCULAR COMPLICATIONS OF DIABETES develop microvascular complications even as late as 30-40 years after the onset of the disease. On the other hand a small minority may have severe retinopathy after only 5-7 years. Clustering of nephropathy for example has been observed in some families and the history of essential hypertension in a first-degree relative is associated with an increased risk of nephropathy in the family member with type 1 diabetes. In WESDR there were no obvious differences between people with type 1 and type 2 diabetes in the incidence of microvascular complications in relation to rising HbAiC. In the UKPDS the risk of each of the microvascular and macrovascular complications of type 2 diabetes was strongly associated with hyperglycaemia as measured by HbAiC. There was no evidence of a threshold and there was a threefold increase over the range of 6 to 10 Fig. . Despite all these studies demonstrating a clear relationship between hyperglycaemia HbA1C and the development of microvascular complications the reasons remain obscure. Although glycosylated haemoglobin reflects recent 3 Ề t 11 1 1 1 ỉ Ĩ Ỉ-- Ỉ-Ỉ--- Ĩ 1 1 1 1 1 1 1 1 1 1 1 1 40 45 50 55 60 65 70 Age years High density lipoprotein cholesterol mmol l 3 Low density lipoprotein cholesterol mmol l 40 45 50 55 60 65 70 Haemoglobulin A1c Systolic blood pressure mmHg never ex- current smokers smokers smokers Fig. Estimated hazard ratios for significant risk factors for coronary artery disease occurring in 335 out of 3 055 diabetic patients. BMJ 1998 316 823-828 with permission. CHAPTER 2 RISK FACTORS 19 glycaemic control there are inevitably differences between individuals regarding the rates of formation and breakdown of glycated haemoglobin and no clear answers about how these may relate to risk of microvascular complications. A single HbA1C must be interpreted with
