Blood pressure pills taken by millions of patients could raise the risk of lung cancer by almost a third, according to new research.
A study involving almost one million Britons found those on Ace inhibitors for at least 10 years (ACEIs) were up to 31 per cent more likely to develop the disease.
The drugs work by blocking an enzyme which narrows blood vessels, and raises blood pressure.
The risk rose over time, with those on the drugs for five years at 22 per cent risk, compared with other blood pressure lowering drugs such as beta blockers.
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Researchers warned that although the relative risk was small, the vast numbers that take the drugs make the results concerning. In 2017 the NHS issued around 22 million prescriptions for Ace inhibitors.
Lead author Prof Laurent Azoulay, a cancer epidemiologist at McGill University in Montreal, Canada: "Although the magnitudes of the observed associations are modest, ACEIs are one of the most widely prescribed drug classes.
"Thus, small relative effects could translate into large absolute numbers of patients at risk for lung cancer."
Previous evidence has linked ACEIs to lung cancer through the build-up of chemicals called bradykinin and substance P, which have both been found in tumours.
The study, published in The BMJ, was based on 992,061 men and women in Britain who started taking a new anti-hypertensive drug between 1995 and 2015.
They were at least 18 years of age, with no previous cancer, and were followed up for an average of 6.4 years, during which time 7,952 cases of lung cancer were identified.
The results held after taking into account factors that could potentially influence them such as age, sex, body mass index (BMI), smoking, drinking and history of lung diseases.
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