Researchers say ACE inhibitors can increase your lung cancer risk, but other experts say the benefits outweigh the risks.

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ACE inhibitors can lower your blood pressure as well as reduce your risk for congestive heart failure. Getty Images

Heart disease kills more than half a million people every year in the United States.

Researchers now want to know if one of the most popular drugs prescribed to cut that cardiac risk is increasing the risk of lung cancer instead.

Angiotensin converting enzyme (ACE) inhibitors are heart medications that expand blood vessels, improving circulation and reducing the heart’s workload.

“ACE inhibitors are the mainstay of treatment, not just for high blood pressure, but also for congestive heart failure and to prevent heart attacks,” Dr. Syed Jafri, an oncologist with McGovern Medical School at UTHealth/UT Physicians and Memorial Hermann Hospital in Texas, told Healthline.

ACE inhibitors are even prescribed to prevent kidney damage in some cases of type 2 diabetes.

The most common side effect is a persistent dry cough. Other possible side effects may include headache, dizziness, or rash.

According to an observational study recently published in The BMJ, researchers found ACE inhibitors were associated with an increased risk of lung cancer when compared with a similar type of blood pressure medication known as angiotensin receptor blockers (ARBs).

“ARBs and ACE inhibitors work in very similar ways to control blood pressure, the biggest difference being that ACE inhibitors can increase levels of two substances in the lungs: bradykinin and substance P,” Jafri said.

“ACE inhibitors,” he added, “can also cause coughing in certain patients. In these cases, ARBs are usually substituted to relieve this symptom.”

Canadian researchers working at the Jewish General Hospital and the University of Toronto used the records of 992,061 British patients who were first prescribed blood pressure drugs between January 1995 and December 2015.

They identified 335,000 patients who were treated with ACE inhibitors, 29,000 with ARBs, and 101,000 who were prescribed both ACE and ARB inhibitors.

The most commonly prescribed drugs were ramipril, lisinopril, and perindopril.

All the study participants had at least one year of health records before and after their first prescription of an ACE inhibitor, ARB, or other blood pressure drug, including beta-blockers and calcium channel blockers.

Lung cancer was diagnosed in 7,952 of the 900,000 patient cohort over a six-year follow-up period.

After researchers considered smoking and other potential factors, ACE inhibitor use was associated with a 14 percent increased risk for lung cancer compared to ARB use.

That risk increased to 31 percent after 10 years.

Asked if the risk of lung cancer outweighed the benefits of taking ACE inhibitors, Jafri said, “I don’t think so. I think the benefit of using ACE inhibitors far outweighs the comparatively small risk of lung cancer.”

“However, in patients who are already at high risk due to heavy smoking, their doctor may want to discuss quitting before prescribing this type of medication,” Jafri cautioned.

Bradykinin is a type of peptide (protein chain) that causes blood vessels to expand. This helps reduce blood pressure.

ACE inhibitors work by preventing bradykinin from breaking down in the body.

In the study, researchers explained that taking ACE inhibitors causes bradykinin to accumulate in the lungs, which they wrote “has been reported to stimulate growth of lung cancer.”

They added that ACE inhibitor use also causes an accumulation of substance P, which is expressed in lung cancer tissue and “has been associated with tumor proliferation.”

This increased risk, however, wasn’t observed in participants who took ACE inhibitors for five years or less.

A randomized, double-blind, placebo-controlled trial of a medical treatment is the gold standard of research.

In this type of study, some of the participants are given a treatment and others are given a placebo, or fake, treatment. Neither the researchers nor the participants know which is which until the study ends.

This wasn’t that kind of study.

Jafri explains that an observational study can only draw inferences from a sample population. The independent variable — in this case ACE inhibitors — isn’t under researchers’ control.

The risk this type of study finds is relative — it’s the risk to a group.

So, an observational study can’t prove that something directly caused an outcome.

The United Kingdom’s National Health Service (NHS) responded to the study with this statement:

“This increase in risk for individuals is extremely small and is massively outweighed by known risk factors for lung cancer such as smoking. For example, smoking 15 to 24 cigarettes a day increases the risk of lung cancer in men by around 2,600 percent (making their risk around 26 times higher).

“What we can say with confidence is that untreated high blood pressure, which can cause heart attacks and stroke, is a far greater threat to your health than taking ACE inhibitors,” the organization stated.

“A large number of people were looked at for many years and compared with people who didn’t take this type of drug to find a very small increase in lung cancer risk,” Jafri noted. “This is definitely not the level of risk that should stop someone from taking ACE inhibitors to treat hypertension or heart disease.”

A peer-reviewed research study conducted in the United Kingdom and published in The BMJ concluded that taking ACE inhibitor drugs for five years or more increased the risk of lung cancer.

This was an observational study, so it couldn’t prove that it was these drugs that actually caused the cancer to develop.

According to the United Kingdom’s National Health Service, this study found the risk of developing lung cancer from using ACE inhibitors is actually quite small.