Diabetes and Hypertension Diabetes mellitus and hypertension coexist more commonly than predicted by chance, perhaps three times more. Of the 10 percent of diabetics with the insulin-dependent form (type I), hypertension is seen in most of the 40 percent who develop nephropathy. In the 90 percent of diabetics with non-insulin-dependent (NIDDM) (type II), almost all of whom are obese, hypertension is more common than among obese people without diabetes. The connection between hypertension, diabetes, and obesity is even stronger in those whose obesity is predominantly upper body, comprising the major components of the insulin resistance syndrome. Complications The diabetics in Framingham suffered almost twice as many strokes, three times more peripheral vascular disease and heart failure, and twice the number of coronary events than did non-diabetics. All of these are increased further when hypertension accompanies diabetes. The microvascular complications, retinopathy in particular, also are increased by hypertension. All diabetics should be carefully checked for microalbuminuria. If present, hypertension and diabetes should be carefully controlled to slow the progression of glomerulosclerosis. The degree of BP reduction needed to maximally protect is unknown, but it is likely lower than the traditional goal of just below 140/90. Antihypertensive Therapy For the 90 percent with NIDDM (type II), the most useful therapy is weight reduction. If weight can be lost through diet and exercise, marked improvements in insulin resistance can be accomplished. If antihypertensive drugs are needed, they should be chosen carefully, with recognition of their many possible adverse effects. Christlieb and the Canadian Hypertension Society recommend the use of either an ACE inhibitor or a CEB for initial therapy for diabetics hypertensives, with a diuretic as a second step. ACE inhibitors are proving to be the best choice in the presence of diabetic nephropathy, slowing the progress of renal damage even when hypertension is not present. Significant improvements in insulin sensitivity and glucose tolerance have been observed to persist for 12 months after replacing B-blocker therapy with ACE inhibitor therapy. The improvement noted by Lithell with captopril has been observed with other ACE inhibitors as well. Antidiabetic Agents Outside the United States, metformin is being used to improve insulin sensitivity and help control diabetes. In short-term studies, it also lowers blood pressure. In the future, other agents which act similarly (eg, ciglitazone) may be available. Dyslipidemia Hypertensives have a higher prevalence of dyslipidemia even if they are not on therapy; the two are common to certain conditions including upper body obesity, diabetes, and alcohol abuse. Even without these mechanisms, more hypercholesterolemia is found among hypertensives than among age and sex matched normotensives. Hypertensives should be assessed for lipid status before antihypertensive therapy is instituted; if hyperlipidemia is present, appropriate diet and drug therapy should be provided. The two most widely used antihypertensive agents, diuretics and beta-blockers, may induce dyslipidemia. Even though these effects may not persist in all patients, in some they last for five years or longer. Some discount the importance of these changes, but they are almost as large as the percentage of positive changes noted in trials of lipid-lowering drugs that have shown protection from coronary disease. If either a diuretic or a non-ISA beta-blocker is used, the total and HDL cholesterol levels should be rechecked after 2 to 3 months. If a significant alteration has occurred, another drug should be considered or an appropriate lipid-lowering regimen instituted. Fortunately, the other classes of drugs either are lipid-neutral or may actually improve the lipid status.
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