ABSTRACT
Most people with type 2 diabetes are aged over 40 years, which is the youngest included in randomized clinical trials of statins. There are a small (and sadly increasing) group of type 2 patients younger than this. Should they receive treatment? In the author’s view, the answer is irrefutably yes. Such patients are almost invariably grossly obese, with a panoply of other risk factors and a lifetime risk of premature death that is appallingly high. The argument then turns to type 1 diabetes. What is their CVD risk? This is a difficult question to answer, partly because CVD risk is irretrievably linked with renal disease. This makes it difficult to interpret older series of patients from before the era of renal replacement and medications such as angiotensin-converting enzyme inhibitors that delay the progression of renal disease, because such patients survive now long enough to die prematurely from CVD. Moreover, short-term observational studies underestimate cumulative CVD risk by omitting the accumulation of CVD deaths that have already occurred, and studies based on clinic populations are biased towards attendees with diabetes of relatively short duration and may even exclude any with preexisting CVD. Thus, the true impact of CVD in the type 1 diabetic population in general may be underestimated. The Diabetes UK cohort study is likely to be
most representative of typical type 1 patients. It reveals that, in both men and women, and certainly between the ages of 40 and 50 years, CVD risk has risen to the point where it generally exceeds the level at which statin treatment should be prescribed.22,23
These findings can be summarized by the statement that the CVD risk in a male type 1 diabetic patient is equivalent to that in a non-diabetic 20 years older, and the risk in a type 1 woman is equivalent to one more than 20 years older22 (see Chapter 11). Both the risk and the evidence from meta-analysis justify the treatment of all type 1 and 2 diabetic patients aged 40 years or more. Furthermore, not distinguishing between type 1 and type 2 diabetics means that the guidelines are easier for the non-specialist, who is frequently not able to make such a distinction in insulintreated patients. In the case of type 1 patients, the most contentious area has become which of those aged less than 40 years should receive statin treatment. Certainly some of these patients should receive statin treatment from early adulthood. Whether their risk is in general as high as that in, say, heterozygous familial hypercholesterolaemia (FH) is uncertain. Were this to be the case, a similar statin treatment policy might be appropriate (see Chapter 4). It is already justifiable in those whose CVD risk is increased because of additional CVD risk factors. In particular this applies to diabetic nephropathy and other microvascular complications such as retinopathy, with which nephropathy is highly linked. Hypertension in a young type 1 diabetic is also likely to indicate an exceptionally high lifetime risk, as is a particularly high cholesterol level or features of metabolic syndrome, which is becoming an increasing problem in type 1 diabetes patients who become overweight. This is recognized in the JBS2 guidelines (Box 10.1).18 The ATPIII recommendations adopt similar principles for statins in diabetes and also make no distinction between type 1 and 2 diabetes.16 The guidance is very similar in the UK and USA18,24 and is currently being revised in Europe. The same LDL cholesterol intervention thresholds as in pre-existing atherosclerotic CVD should be used, meaning that in the USA there is the option to begin statin treatment at LDL cholesterol levels as low as 70 mg/dl (1.8 mmol/l). In type 1 diabetes, there is no reliable way of basing therapeutic decisions on the serum cholesterol to HDL cholesterol ratio, or indeed the LDL cholesterol to HDL cholesterol ratio, because of the high HDL levels associated with insulin therapy in type 1 diabetes.25,26 These do
not provide the same degree of cardiovascular protection as is more generally the case.
