High blood pressure, or hypertension, affects billions of people globally. While its connection to heart disease and stroke is well-established, researchers are exploring its relationship with cancer. The evidence suggests a complex relationship that is not always direct, but one that involves shared biological processes and common risk factors.
The Statistical Link Between High Blood Pressure and Cancer
Large-scale population studies have identified a statistical correlation between high blood pressure and an increased risk of developing certain types of cancer. This association is most consistently observed with kidney cancer, also known as renal cell carcinoma. Research indicates that individuals with hypertension have a higher risk of developing this malignancy compared to those with normal blood pressure.
The evidence also points to a link with other cancers, though the strength of the association can vary. Prospective studies have shown that hypertension is a risk factor for colorectal cancer. Some meta-analyses suggest a higher risk for postmenopausal breast cancer and endometrial cancer in individuals with high blood pressure. For breast cancer, some studies have found that women with hypertension have about a 15% increased risk.
These epidemiological studies reveal that the two conditions often occur together, but they do not definitively prove that high blood pressure directly causes cancer. The increased risk appears to grow with the duration of hypertension, particularly when it is diagnosed before the age of 50.
Potential Biological Pathways
Scientists are investigating several biological mechanisms that could explain how chronic high blood pressure might contribute to cancer. One area of focus is chronic inflammation. Hypertension can promote a state of persistent, low-grade inflammation, and such inflammation can be a driver for cancer development by creating a cellular environment that fosters tumor growth.
Another proposed pathway involves the renin-angiotensin system (RAS), a hormone system that regulates blood pressure. The activation of the RAS in people with hypertension has been implicated in processes like cellular proliferation and tissue remodeling, which could elevate cancer risk. This system also stimulates angiogenesis, the formation of new blood vessels that tumors require to grow and metastasize.
A third mechanism is oxidative stress, an imbalance between free radicals and antioxidants in the body. High blood pressure can lead to increased production of reactive oxygen species, causing oxidative stress. This condition can damage cellular components, including DNA, and this accumulated damage can lead to mutations that initiate cancerous cells.
Researchers have also identified specific proteins that may serve as a molecular link. The G-protein coupled receptor kinase 4 (GRK4) protein, known to cause hypertension, has been found in breast cancer cells but not in normal breast tissue. This protein is regulated by an oncogene called c-Myc, suggesting a direct molecular connection between the two conditions.
Influence of Shared Risk Factors
The connection between high blood pressure and cancer is complicated by shared risk factors. Many lifestyle factors that contribute to hypertension also independently increase a person’s cancer risk. This overlap means the observed association may not be a case of one causing the other, but a third factor causing both, which makes it difficult to isolate the effect of hypertension alone.
Common examples include:
- Obesity, as excess body weight is a cause of high blood pressure and is linked to an increased risk for colorectal, breast, and kidney cancer.
- A diet high in processed foods and sodium.
- A sedentary lifestyle.
- Smoking, which is a major cause of lung cancer and also contributes to high blood pressure.
Hypertension Medications and Cancer Risk
The question of whether medications used to treat high blood pressure affect cancer risk has been a subject of scientific research. Over the years, some studies raised questions about potential links between certain classes of antihypertensive drugs and cancer. For example, early studies suggested a possible association between thiazide diuretics and renal cancer.
It is difficult to separate the effects of the medication from the effects of the hypertension itself, as the use of these drugs is highly correlated with the disease. More recent and extensive research, including meta-analyses of clinical trials, has provided a clearer picture. These large-scale analyses have not found conclusive evidence that blood pressure-lowering medications increase the overall risk of developing cancer or dying from it.
There have been separate issues related to impurities in some medications. Specific recalls of certain angiotensin II receptor blockers (ARBs) occurred due to contamination with N-Nitrosodimethylamine (NDMA), a substance classified as a probable human carcinogen. This contamination was a manufacturing issue, distinct from the primary mechanism of the drug itself.
Current evidence indicates that the major classes of blood pressure medications, such as ACE inhibitors, ARBs, and calcium channel blockers, do not inherently increase cancer risk.