Women who use antibiotics for more than two months at a time are at increased risk of suffering a heart attack or stroke, research suggests.
Experts believe the long-term use of the drugs wipes out healthy bacteria in the gut – creating an imbalance that increases inflammation, narrows blood vessels and ends up damaging the heart.
They think this creates a cumulative effect, so the more frequently a woman uses antibiotics during her lifetime, the greater the eventual risk.
The researchers, who tracked 36,500 women in the US, found over-60s who used antibiotics for more than two months were 32 percent more likely to develop heart disease in the next eight years than those not taking the drugs. For those aged 40 to 59, there was a 28 percent increased risk.
For younger women aged under 40, there was no discernible effect.
Researcher Dr. Yoriko Heianza, from Tulane University in New Orleans, said: ‘By investigating the duration of antibiotic use in various stages of adulthood we have found an association between long-term use in middle age and later life and an increased risk of stroke and heart disease during the following eight years.
‘As these women grew older, they were more likely to need more antibiotics, and sometimes for longer periods of time, which suggests a cumulative effect may be the reason for the stronger link in older age between antibiotic use and cardiovascular disease.’
The researchers, who published their findings in the European Heart Journal, stressed that even though the overall relative risk increased, for each individual the absolute risk remained small.
For every 1,000 women taking antibiotics for at least two months, just six would be likely to experience damage to their hearts or arteries, they said.
Antibiotics are designed to kill dangerous bacteria that cause illness and infection.