The number of people with diabetes (high blood sugar) in the U.S. continues to increase due to our aging population, sedentary lifestyle, and the number of overweight (obese) people. Hypertension (high blood pressure) is twice as common in people with diabetes than in people without diabetes. There are two types of diabetes: the classic insulin-dependent form, or type 1 (often diagnosed at a young age and makes up about ten percent of all diabetics), and the insulin-independent form, or type 2 (usually presents around middle age and accounts for 90 percent of all diabetics.)
In the two types of diabetes, obesity is present in most of the people with type 2. Hypertension is also more common in people with type 2 diabetes. On the other hand, kidney malfunction (nephropathy) is very common in type 1 diabetics—present in about 40 percent. In general, diabetics have increased risks of stroke, heart attack, heart failure, and peripheral vascular disease than non-diabetics. These risks are increased further in the presence of hypertension.
How Does Diabetes Cause Hypertension?
Although we don't know all the reasons why hypertension is very common in diabetics, the little that we do know allows the belief that it is the increase in blood insulin in both types of diabetes that promotes hypertension by affecting key checkpoints in the body. For example, increased blood insulin makes the blood vessels widen (vasodilate) and this widening of the blood vessels affects the sympathetic nervous system that increases blood pressure (BP), directly or indirectly, by making the kidney retain salt. Another way the increase in blood insulin can lead to increased blood pressure is by promoting atherosclerosis, which hardens the blood vessels.
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It is also believed that those diabetics (especially type 2) who live with untreated high blood sugar for a long time are more likely to have hypertension due to early atherosclerosis.
What Blood Pressure is Considered Abnormal if I am Diabetic?
For my patients with type 2 diabetes and/or family history of both diabetes and hypertension, I encourage them to have their blood pressures followed very closely. Usually, if the blood pressure remains equal or greater than 140/90 over two or more weeks of several measurements, the diagnosis of hypertension is made. However, the diagnosis of hypertension has to be entertained and probably be made if you are diabetic and have blood pressure in the borderline range of 130-139/85-89 mm Hg.
The Importance of Lifestyle Modification (Weight Loss, Exercise, and Diet)
Lifestyle modification in the form of weight loss through exercise and diet is particularly important in diabetics. Obesity increases your chances of having diabetes (especially type 2) and/or hypertension. It is generally agreed that the best way to prevent hypertension or to reduce BP is to maintain ideal body weight or lose weight if you are obese. Many of my patients often ask what ideal body weight means and how they can find theirs. Ideal body weight is basically a weight that is calculated using your height and your sex, matched against a standard (what an average person of your height and sex should be). It is different for men and women.
Ideal body weight
For example, to estimate the ideal body weight of a woman with height of five feet, three inches, you will allow 100 pounds for the five feet and then add five pounds for each additional inch. Therefore, the above woman's ideal body weight will be 115 pounds (five feet = 100 pounds, three inches = 15 pounds (5 x 3). For men you allow 106 pounds for five feet and six pounds for each additional inch, making the ideal body weight for the assumed man to be 124 pounds. If the woman in the above example is my patient with diabetes and weighed 138 pounds (20 percent over ideal weight for a five-foot, three-inch tall woman), I would probably recommend a weight reduction program for her even if she has no hypertension at this time.
If she were ten percent or less over her ideal weight I probably would not recommend anything. Usually I start by recommending fewer calories each day. One way to estimate the number of calories needed to maintain an ideal body weight is to determine the activity level of the person. For example, a very active person has activity level of 17, relatively active = 15, inactive = 13. So if the above patient is relatively active (activity level = 15), the total calorie need per day to maintain her ideal body weight of 115 pounds will be 1,725 calories (115 x 15). A healthy diet for her should consist of food low in saturated fat and total fat, low in salt and cholesterol, but high in fiber. The goal is to maintain a diet with no more than 30 percent of calories from fat (approximately 20 percent unsaturated fat and 10 percent saturated fat). I emphasize to my patients to eat multiple servings of fruits, vegetables, and variety of grains (cereal, rice, etc.), especially whole grains, low-fat dairy products, and low-calorie soft drinks.
For exercise, I usually recommend at least 30 minutes of moderate exercise (biking, swimming, walking, and jogging) a day for adults and about 60 minutes for younger patients.
Beginning Drug Therapy and Target Blood Pressure
I usually initiate antihypertensive drug therapy (blood pressure medication) in addition to lifestyle modification as soon as any of my diabetic patients is found to have high normal BP (130-39/85-89). This treatment strategy is different and more aggressive compared to treatment of hypertension in people without diabetes in whom lifestyle modification alone would have been my initial approach. Reduction of BP in diabetics saves lives from complications of heart disease.
The ideal BP target in diabetics is 120/80 or below, although this target is lower than target BP in people without diabetes, clinical trials have shown that this target is most beneficial in terms of reducing complications in this population of patients.
What Drugs are Best for Me?
Angiotensin-Converting Enzyme Inhibitors (ACEIs) (Lisinopril, Enalapril, Ramipril, or Captopril) are my preferred first-line drugs for the treatment of hypertension in diabetics, especially in type 1 diabetics with nephropathy and/or heart failure. The benefits of the ACEIs over other medications include:
- prolongation of life in diabetics with hypertension and heart failure
- improvement in exercise tolerance
- reduction in the level of angiotensin II in the blood (angiotensin II has negative effect to the functions of the heart).
- These drugs also have no effect on glucose or lipids, decrease proteinuria (protein in the urine) and rate of kidney damage.
- They rarely cause orthostatic hypotension, rarely cause impotence and minimize adverse metabolic effects of diuretics when used together.
Angiotensin-Receptor Blocker (ARBs) such as Losartan, Irbesartan, or Candesartan are similar to the ACEIs in their action, but have fewer side effects of coughing and rash that are seen in the use of ACEIs.
Some clinical studies have found them to be effective in controlling blood pressure, however, they have not been around as long as the ACEIs and clinical trials have not confirmed and compared their effects in a large number of patients (such studies are still ongoing). They are, therefore, not used as first-line agents all the time. I use them in my diabetic patients with hypertension and/or heart failure if they cannot tolerate the ACEIs due to persistent cough or rash.
Other medical problems that my diabetic patients have (e.g., irregular heartbeats, benign prostatic hyperplasia (BPH), osteoporosis, angina, isolated systolic hypertension (ISH), or heart failure help guide the choice of medications I use in conjunction with first-line agents. For example, in those diabetics with history of angina, prior heart attack, or irregular heartbeats, I tend to use a beta-blocker like Atenolol, Bisoprolol, or Metoprolol. These drugs reduce blood pressure in addition to reducing the amount of work the heart has to do by reducing heart rate and "pumping of the heart" (cardiac output) They have been shown to prevent second heart attacks and dangerous abnormal heartbeats (arrhythmias).
For diabetic male patients with BPH and hypertension, I add an alpha-adrenergic blocker (drugs like Doxazosin, Prazosin, or Terazosin) to an ACEI. These drugs reduce the symptoms of BPH by their action on smooth muscles as well as help control BP. In general, I tend to start these medications at a low dose of the long-acting, once-daily formulations and increase gradually until maximum dose is achieved depending on patient response. I consider adding a second agent from a different class if, while the patient is tolerating the first agent, BP control is not achieved. Sometimes I may withdraw the first medication completely and substitute with a medication from a different class if there are too many side effects or if the drug is not effective. It is not uncommon for me to use three medications from different groups in order to achieve desired blood pressure in some of my diabetic patients.
It is important to follow blood sugar and blood pressure very closely in diabetics for early diagnosis and prompt initiation of therapy. This strategy will help reduce complications associated with these diseases. I believe that the most critical factor in controlling both diabetes and hypertension is weight reduction through exercise and diet. Since drug therapy is recommended for all diabetics at all stages of hypertension (mild, moderate and severe), I usually choose antihypertensives carefully and pay special attention to their side effects. Monitoring of lipid levels (cholesterol, etc.) and blood sugar levels are important because some blood pressure medications may affect their levels. With early diagnosis, weight reduction through diet and exercise, choice of appropriate medication, and close monitoring, hypertension in diabetics will have fewer complications.