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.
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.
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.
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.
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.