Causes
Hypertension is referred to as essential (primary) when the doctor is unable to identify a specific cause. It is by far the most common type of high blood pressure. The causes of this type, while unknown, are likely to be a complex combination of genetic, environmental, and other factors.
Genetic Factors. A number of genetic factors or interactions between genes play a major role in essential hypertension. Experts think that the chromosomes (13 and 18) house the genes responsible for blood pressure regulation, although pinning down the range of specific genes involved in hypertension is more difficult.
- Genes under intense study are those that regulate a group of hormones known collectively as the angiotensin-renin-aldosterone system. This system influences all aspects of blood pressure control, including blood vessel contraction, sodium and water balance, and cell development in the heart.
- Studies suggest that some people with essential hypertension may inherit abnormalities of the sympathetic nervous system. This is the part of the autonomic nervous system that controls heart rate, blood pressure, and the diameter of the blood vessels.
Insulin Resistance and Type 2 Diabetes. Hypertension is strongly associated with diabetes, both type 1 and type 2. Kidney damage is generally the cause of high blood pressure in type 1 diabetes. Obesity and insulin resistance are the factors associated with hypertension in type 2 diabetes, the more common type. People with type 2 diabetes generally have normal or high levels of insulin, a critical hormone in the metabolism of sugar. However, they are unable to use the insulin, a condition called insulin resistance. Without insulin, blood glucose (sugar) levels rise, the hallmark of diabetes.
People who have insulin resistance or full-blown diabetes plus hypertension have a significantly greater chance for heart attack, kidney disease, and stroke than people who have only high blood pressure.
Obesity. Obesity on its own has a number of possible effects that could lead to hypertension. It may blunt certain actions of insulin that open blood vessels, and it may cause structural changes in the kidney and abnormal handling of sodium. It is also associated with alterations in the systems that regulate blood flow.
Kidney Disease. Kidney disease is the most common cause of secondary hypertension, particularly in older people.
Coarctation of the Aorta. Narrowing of the aorta soon after it leaves the heart can cause high blood pressure, which often shows up in one of the arms.
Other Medical Conditions. Adrenal tumors, pheochromocytoma, and Cushing syndrome can all present with hypertension.
Medications. Certain prescription and over-the-counter drugs can cause temporary high blood pressure. They include:
- Corticosteroids when given by mouth or intravenously
- Nonsteroidal anti-inflammatory drugs (NSAIDs) -- such as ibuprofen (Motrin), naproxen (Aleve), and aspirin -- may cause secondary hypertension as well as other complications. In one important study, women who used an NSAID for 5 or more days a month had a significantly higher risk for hypertension. The more often they used these drugs, the higher the risk. A 2007 study indicated that NSAIDs also increase the risk for hypertension in men. A 2005 study found that NSAIDs increase the risk for kidney failure, and that the risk is significantly greater for all patients with hypertension. Patients who took diuretics along with NSAIDs had 11.6 times the risk of developing acute kidney failure compared to non-NSAID users. The relative risk for calcium channel blockers and NSAIDs was 7.8. The researchers advised that patients with hypertension or heart failure should use NSAIDs with caution.
- Cold medicines containing pseudoephedrine have also been found to increase blood pressure in hypertensive people, although they appear to pose no danger for those with normal blood pressure.
- Oral contraceptives ("the pill") increase the risk for high blood pressure, particularly in women who are older than 35 years, obese, smokers, have strong family history of hypertension, or some combination. Stopping the pill nearly always reduces blood pressure.
Alcohol.An estimated 10% of hypertension cases are caused by alcohol abuse (three or more alcohol drinks a day), with heavier drinkers having higher blood pressure. Women may be more sensitive than men to the blood pressure effects of alcohol. Moderate drinking (one or two drinks a day) has benefits for the heart and may even protect against some types of stroke. In particular, red wine may have chemicals that help blood pressure.
