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HIGH BLOOD PRESSURE AND DIABETES: DOUBLE TROUBLE?
Dr. S.M.Sadikot.
Hon. Endocrinologist,
Jaslok Hospital and Research Centre,
Mumbai 400026

Diabetes and high blood pressure (hypertension) are serious disorders. Each of them can lead to severe complications in the body and in many cases they affect the same organs. Thus, one would naturally assume that if one has diabetes and high blood pressure, the ill effects in the body would be double.


Right?………………Wrong!


Having diabetes and high blood pressure is not a case of adding one and one and making two. It is more like eleven! The ill effects of diabetes and high blood pressure, when a person has both, are increased much more than one would imagine.


The problem is that many patients with diabetes also have high blood pressure! It has been estimated that high blood pressure is twice as likely to be present in a person with diabetes as compared to someone who does not have diabetes.


In order to understand the problems which high blood pressure can cause, it would seem proper to learn a little bit about blood pressure.


What is blood pressure?


The various parts of the body need nourishment. They get this from the blood that flows to them in the arteries supplying the various parts of the body. The heart "pumps" the blood into the arteries, but for the blood to flow through the arteries, especially the smaller vessels, it literally has to force apart the walls of the arteries, so that it can pass through. It is this pressure which the blood has to apply to the arteries to allow it to flow through which is called "blood pressure"


Thus, one could say that it mainly depends on the resistance offered by the arteries to the blood flow and will also depend on the amount of blood which has to flow. This again is obvious. If more blood has to flow the walls of the arteries have to be kept open wider and for a longer time period. Thus, the heart will have to pump that much harder!


Why does my Doctor talk of the Upper and Lower pressures?


Basically, when your doctor tells you about the upper and lower pressure readings, he is talking about what we call the "Systolic" and "diastolic" blood pressure readings.


Although most of us do not realize it, the heart pumps blood more than 100,000 times a day! Each time it beats, a blood is pumped into the arteries and this blood has to overcome the resistance of the vessels. This gives rise to the upeer or the higher reading which is the systolic pressure. In between heartbeats, when the blood flow decreases in the arteries, the pressure on the walls is lowered and this gives rise to the lower or the diastolic pressure readings.


That is why blood pressure is reported as two numbers, e.g., 120/80. The first, higher number (systolic) is the pressure of the blood against the artery walls when the heart contracts (e.g., 120). The second, lower number (diastolic) is the pressure against the artery walls when the heart relaxes between beats (e.g., 80).


Desirable blood pressure

Desirable Blood Pressure120systolic
For Healthy Adults80diastolic

Any blood pressure reading that consistently stays at 140/90 or higher is considered high blood pressure.


For diabetic subjects high blood pressure is defined by a blood pressure up to 130/85 mmHg, or 120/80 which is better still, especially if they have kidney dysfunction.


High Blood Pressure


We have seen that the blood pressure depends on the resistance offered by the arteries to the flow of blood. If the vessels are wider ( more "open") then, the heart has to do less work in pumping the blood through. But if for some reason, the same vessels become smaller, more pressure is needed for the same amount of blood to flow through them. This increase in pressure, which is more than normally required, is called high blood pressure.


What Causes High Blood Pressure?


In the vast majority of cases, we do not know the reason and the high blood pressure is called "essential" hypertension. In a few cases, especially in those who are young, it is possible to find a cause leading to the high blood pressure and in these people are said to have "secondary" hypertension.


Although a lot of research is being carried out on why people with diabetes are at a higher risk for having high blood pressure, we are still to arrive at any definite answer.


But the fact remains that high blood pressure is much more common in a person with diabetes and that together they are a very deadly "duo" unless both, diabetes and the high blood pressure are well treated and kept at optimal levels.


Who is at higher risk?


  • People with close blood relatives who have it. It "runs" in families.
  • People with diabetes
  • People over 30. although more and more younger people are seen to have it.
  • Overweight people, especially those who have a high waist to hip ratio.
  • People who use too much salt
  • People who use too much alcohol
  • Women who take birth control pills
  • People who aren't active
  • Pregnant women


What problems can high blood pressure cause?

  • Atherosclerosis ( blocking or narrowing of the vessels)
  • Stroke
  • Heart attack
  • Heart failure
  • Kidney failure


Arteriosclerosis is hardening of the arteries. The walls of arteries have a layer of muscle and elastic tissue that makes them flexible and able to dilate and constrict as blood flows through them. When your blood pressure remains high for a long period of time, these vessel walls get affected and become harder and less flexible. They are unable to dilate when the heart pumps blood and more blood has to pass through. Similarly, in the diastolic phase, when the walls have to get back into their normal shape. More often than not the net results is a narrowing of the vessels. This also leads to damage to the inner linings of the arteries. Cholesterol and fats are more likely to build up on the walls of damaged arteries, making them even narrower. Blood clots can also get trapped in narrowed arteries, blocking the flow of blood.


Arteries narrowed by arteriosclerosis may not deliver enough blood to organs and other tissues. Reduced or blocked blood flow to the heart can cause a heart attack. If an artery to the brain is blocked, a stroke can result.


Hypertension makes the heart work harder to pump blood through the body. The extra workload can make the heart muscle thicken and stretch. When the heart becomes too enlarged it cannot pump enough blood. If the hypertension is not treated, the heart may fail.


The kidneys remove the body's wastes from the blood. If hypertension thickens the arteries to the kidneys, less waste can be filtered from the blood. As the condition worsens, the kidneys fail and wastes build up in the blood.


When you read the consequences of high blood pressure, you will realize that many of these are very similar to those caused by diabetes. So, if a person has both high blood glucose as well as high blood pressure, the problems get multiplied!


Not only is the atherosclerosis more severe, it occurs at a much earlier age and progresses much faster when one has both diabetes and high blood pressure. Is it any surprise that heart problems and paralytic strokes are so much more common in people with diabetes who also have high blood pressure!


We have seen that foot problems are very a very serious complication in a person with diabetes. Narrowing or complete blocks of the arteries going to the feet does not allow blood to flow to the feet which is an important factor in ulcers of the feet not healing well and leading to increased numbers of amputations. Gangrene of the leg, often precipitated by an infection, is also more common, increasing the numbers of people who have to undergo amputations.


We know that diabetes affects the small vessels (diabetic microangiopathy) which is involved in causing the eye and kidney problems in patients with diabetes. The presence of high blood pressure in people with diabetes, increases these eye and kidney problems in "leaps and bounds"!


The kidneys merit a special mention. Not only does high blood pressure and diabetes lead to kidney damage, but the kidney damage itself leads to an increase in the blood pressure levels. You can imagine the viscious cycle. The kidneys are damaged by the high blood glucose levels and the high blood pressure and this damage, in turn, increases the high blood pressure!


As importantly, when the kidneys are damaged, the control of the blood glucose levels becomes very difficult with a tendency for the blood glucose levels to fluctuate from very high to very low blood glucose levels without any "apparent" cause. The fluctuations, the high blood glucose levels and the "hypos" that occur increase the damage not only to the kidneys but the other organs which are "targeted" in diabetes.