Certain blood pressure drugs may carry an increased risk of lung cancer, a new study suggests.
Researchers examined data on patients taking two different types of drug used to treat hypertension.
They analysed the use of angiotensin converting enzyme inhibitor drugs (ACEIs) compared with another group of blood pressure drugs called angiotensin receptor blockers (ARBs).
The study, published in The BMJ, saw researchers examine data from the UK Clinical Practice Research Datalink to compare patients taking these different types of drugs.
Experts from Northern Ireland and Canada looked at data on almost a million patients started on anti-hypertensive drugs between 1995 and 2015.
They then followed up patients for an average of 6.4 years.
A total of 7,952 lung cancer cases were identified during this timeframe.
The authors found that patients using the ACEI drugs were 14 per cent more likely to have developed lung cancer.
The length of time patients were on the drugs was also linked to an increased likelihood of developing the disease.
Those who had used the drugs for five years or more were found to have a 22 per cent increased risk and those who had used the drugs for 10 years or more had a 31 per cent higher chance of developing lung cancer, they found.
The study is an observational one, so no firm conclusions can be drawn about cause and effect, but the authors called for further research to explore the link.
"The use of angiotensin converting enzyme inhibitors was associated with a 14 per cent increased risk of lung cancer," they wrote.
"Associations were evident after five years of use and increased with longer durations of use, particularly in patients who used angiotensin converting enzyme inhibitors for more than 10 years.
"The magnitudes of the observed estimates are modest, but these small relative effects could translate into large absolute numbers of patients at risk, so these findings should be replicated in other settings."