How Diabetes Can Lead To Hypertension

Diabetes can result in damage to many parts of your body; unfortunately, uncontrolled blood sugar can ultimately leads to kidney failure, heart problems, and high blood pressure. So, how does diabetes cause high blood pressure? Can getting your blood sugar under control "cure" your hypertension?

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How does diabetes cause high blood pressure?

Diabetes causes hardening of the arteries, known as atherosclerosis¹. Plaque (mainly composed of cholesterol and fat) is deposited in the arteries, which then become hard and resist blood flow. This increases blood pressure, as well as strain on your heart.

Both type 1 and type 2 diabetes² are associated with atherosclerosis, although they can have numerous other underlying causes. Some of those causes can be comorbid with diabetes, such as high cholesterol or obesity, making the issue worse. Prolonged high blood sugar causes changes in vascular tissue that alter enzymes, interact with receptors, and cause oxidative stress. The high blood pressure then aggravates atherosclerosis³, creating a feedback cycle that can easily lead to a heart attack.

Furthermore, despite popular belief, type 2 diabetes⁴ is not "caused" by obesity. Instead, insulin resistance develops in the muscles of lean individuals and obesity is, in fact, a symptom of type 2 diabetes. Type 2 diabetes causes excess fat accumulation, which then makes insulin resistance worse. Obesity aggravates high blood pressure by increasing the amount of work the heart has to do. That said, excessive weight can increase the risk of insulin resistance, resulting in a vicious cycle as diabetes causes weight to increase further.

Finally, there is some evidence that hyperglycemia⁵ (high blood sugar) may directly affect blood pressure. Reducing dietary sugars has been shown to lower blood pressure. Intensive insulin therapy in type 1 diabetics reduces the risk of developing hypertension with age.

Can high blood pressure cause diabetes?

The relationship between diabetes and high blood pressure can go in both directions. A study in Korea⁶ showed that individuals with hypertension are more likely to develop diabetes, and that managing blood pressure in susceptible individuals can reduce the risk of diabetes. However, for this to work, you have to be able to get your blood pressure down to normal ranges.

The study suggests that blood sugar should be checked regularly in people with hypertension, so make sure to talk to your doctor about getting screened regularly.

Correlation versus causation

While it is fairly clear that diabetes can cause damage to arteries that then leads to hypertension, the connection in the other direction is a bit more tenuous.

There is also the fact that both Type 2 diabetes and high blood pressure share risk factors. At least some comorbidity can be explained simply by the fact that if you are predisposed to the one you are likely also predisposed to the other. Common risk factors include:

  1. Excess weight and body fat

  2. Unhealthy eating

  3. Sedentary lifestyle

  4. Stress

  5. Poor sleep habits

  6. Smoking

  7. Older age

Both are influenced by family history, although it can sometimes be hard to tease things out. For example, if you have a family member with type 2 diabetes and high blood pressure, it is possible that they had genes that predisposed them to both...or that their diabetes caused their high blood pressure. This can be hard to establish, especially if your family member is/was older and diagnosed at a time when we had less understanding of how the conditions interact.

Sleep apnea is a specific risk for high blood pressure, but as it induces poor sleep it may also predispose you to type 2 diabetes.

While type 2 diabetes has a strong genetic component, it is aggravated by lifestyle factors. In some cases, people may develop type 2 diabetes without a family history, so it is important to monitor your blood sugar regardless, especially after the age of 45 or if you are overweight and/or prone to weight gain.

What about type 1 diabetes?

Type 1 diabetes is primarily genetic and is not as affected by lifestyle factors. However, type 1 diabetes⁷ still affects blood pressure. Type 1 diabetics tend to have higher systolic blood pressure (the top number) and younger individuals have a higher diastolic blood pressure (the bottom number), which tends to decline faster in old age. Because of this, type 1 diabetics are very prone to isolated systolic hypertension, where only the top number is elevated. There are also indications that your arteries age faster when you are diabetic.

Some people with type 1 diabetes have to take high blood pressure medication to help mitigate these issues. High blood pressure and premature arterial aging is likely a contributing factor to higher levels of heart disease in people with the disease. Keeping your diabetes under control will also help, as will ensuring that you comply with your meal plan and insulin regimen. You should also talk to your doctor about whether you should eat a low sodium diet. Staying physically active will help to keep your diabetes under control and your blood pressure down to normal levels. That said, the correlation is not as strong as with type 2, perhaps because of the shared risk factors that are not as strong with type 1.

Gestational diabetes⁸, which is caused by hormonal changes and weight gain during pregnancy, can also elevate blood pressure and cause a risk of pregnancy complications such as preeclampsia (dangerously high blood pressure that may require early delivery of the baby). Blood sugar levels often return to normal after birth, but sometimes stay elevated, and having had gestational diabetes increases your risk of later developing type 2 diabetes.

How diabetes and high blood pressure "work together"

Having both diabetes and high blood pressure can make some symptoms a lot worse. For example, both conditions can lead to retinopathy, a form of eye disease where blood vessels are damaged in the retina.

Diabetic retinopathy is caused by uncontrolled high blood sugar and can lead to blurred and fluctuating vision and ultimately to vision loss. Small amounts of retina damage may occur before any other symptoms of diabetes, so people at high risk of diabetes due to weight, family history, etc, should be screened regularly for retinopathy by their eye doctor. Hypertensive retinopathy⁹ is typically asymptomatic, but can also cause blurred vision. Having both conditions can increase your risk of going blind, but keeping both under control will help protect your eyes.

The two conditions together greatly increase your risk of heart disease¹⁰ and stroke. Two-thirds of people with type 2 diabetes also have high blood pressure. For type 1 diabetes, the concern is faster aging and stiffening of the arteries, which also increases your risk of heart problems.

Managing diabetes and high blood pressure

Thankfully, many of the same lifestyle changes help control both conditions. Early control of blood sugar can prevent hypertension from developing altogether, although it is not always easy. For non-insulin-dependent diabetics, diet and medication are key to ensuring that the condition does not progress. Lifestyle changes include:

  1. Controlling weight. Although type 2 diabetes causes secondary obesity, it is still aggravated by primary obesity, as is hypertension. Controlling your weight has been shown to prevent prediabetes from becoming diabetes¹¹. You do not need to lose a lot of weight, only between 5 and 7% of your total body weight to see a benefit.

  2. Becoming more physically active. Getting at least 150 minutes of moderate exercise, such as brisk walking, a week can reduce the risk of developing both conditions as well as improve your overall health, mood, and self-esteem.

  3. Eating a healthy diet and cutting down on dietary sugars. There are indications that reducing sugar intake¹² can help keep blood pressure down.

  4. Managing stress and anger. Stress can affect your overall health and has been demonstrated to increase blood pressure.

All of this will help you stay healthy and manage your diabetes and high blood pressure symptoms.

Managing diabetes and high blood pressure

The only way to detect high blood pressure is through regular screening. If you have been diagnosed with diabetes, you should monitor your blood pressure carefully. Most doctors will check your blood pressure and weight every three to six months¹³, depending on how well-controlled your blood sugar is. If you have elevated readings, they will recheck the readings and potentially have you do 24 hours of home monitoring to eliminate transitory spikes and get a better idea of how high your blood pressure is.

You should ensure that you’re eating a diet that helps you control both your blood sugar and your blood pressure. The Dietary Approaches to Stop Hypertension¹⁴ diet plan (DASH) is your best option.

Although primarily designed to control high blood pressure, DASH also limits added sugars. You might need to lower sodium further by using salt substitutes, not adding salt to rice, pasta, or hot cereal, and not buying pre-seasoned or cured meat. The overlap in risk factors, thankfully, makes it easier to eat foods that are beneficial for both conditions. An alternative option is to work with a nutritionist on a plant-based diet. As DASH recommends a certain number of servings of meat, vegetarians and vegans may need to talk to a nutritionist about good substitutes. Vegan and vegetarian diets¹⁵ have also been shown to reduce the risk of hypertension in general.

Always choose whole grains over processed grains such as white bread or white rice. Read labels and check for added sugars, even in items you don't think of as being "sweets." Sugar and corn syrup are sometimes used as preservatives.

Lifestyle changes may not be enough to lower your blood pressure or control your blood sugar. However, your doctor will work with you on the right medications to take. There is a variety of blood pressure medications, but your doctor will try and choose medications that also help with the control of diabetes¹⁶. For most people with high blood pressure, a diuretic is the first choice. However, for people with diabetes, the front line therapies are:

  • Angiotensin-converting enzyme (ACE) inhibitors have been demonstrated to slow the onset of kidney failure.

  • Angiotensin receptor blockers are similar to ACE inhibitors and are used in patients who can't tolerate ACE inhibitors.

You may be given a thiazide diuretic as well and, depending on your situation, beta and/or calcium blockers might be used, depending on your specific condition. Beta-blockers are used for patients with a history of heart problems. Moreover, you may need more than one kind of blood pressure medication and generally, doctors aim for a target blood pressure of less than 130/80 mm Hg. There are typically no significant interactions between metformin (commonly used for diabetes)  and blood pressure drugs. If you are put on blood pressure drugs, do not stop taking them without consulting your doctor.

Type 2 diabetics that need insulin have a specific, potential issue. If your diabetes is poorly controlled and your doctor starts you on insulin therapy as a result, this can cause a temporary increase in blood pressure¹⁷. This temporary increase lasts a few months and eventually comes down to below pretreatment values. This just means that your doctor will keep an eye on your blood pressure after starting you on insulin, especially if you are obese. They may recommend home monitoring to ensure a quick alert if blood pressure becomes dangerously high.

The lowdown

If you have diabetes, you are very likely to develop hypertension. Your doctor will take steps to closely monitor your blood pressure, and may prescribe medication to keep it under control.

Because of the interaction between the two conditions and overlapping risk factors, the same things which help prevent diabetes also help prevent high blood pressure. People with prediabetes should make lifestyle changes that are known to help keep it from progressing to diabetes. These same lifestyle changes can keep your blood pressure within normal levels.

If you have type 1 diabetes, you are still at risk from hypertension, even at a young age, and you should monitor your blood pressure regularly. Reducing salt in your diet can be the best way to help bring blood pressure down.  Follow up with your physician regularly for long-term monitoring to ensure optimum health.

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