Taking antibiotics for a long time during late adulthood may be linked with a higher risk of death among women, according to the latest evidence.

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Antibiotics have saved millions of lives, but they may have a darker side.

Antibiotics have been commonly prescribed by doctors for 70 years.

These drugs have significantly reduced global rates of illness and death from infectious diseases.

However, their widespread use has allowed some infectious organisms to adapt and become resistant to antibiotics.

There are some side effects associated with antibiotics — including feeling sick, diarrhea, and fungal infections of the mouth, digestive tract, or vagina.

Antibiotics and gut microbiota

Scientists already know that the use of antibiotics is linked to changes in gut microbiota, which is the name given to the microorganisms that reside in our digestive tract.

Previously, Medical News Today have reported that a single course of antibiotics can disrupt the gut microbiome for a year. The authors of that study — which was published in the journal mBio — concluded that antibiotics should only be used when "really, really necessary."

In their paper, they write that even a single antibiotic treatment in a healthy person contributes to antibiotic resistance and long-lasting adverse effects in the gut microbiome.

"Gut microbiota alterations have been associated with a variety of life-threatening disorders, such as cardiovascular diseases and certain types of cancer," says new study co-author Lu Qi, a professor of epidemiology at Tulane University in New Orleans, LA.

"Antibiotic exposure affects balance and composition of the gut microbiome, even after one stops taking antibiotics; so, it is important to better understand how taking antibiotics might impact risks for chronic diseases and death."

Prof. Lu Qi

These findings were presented at the American Heart Association's (AHA) 2018 scientific sessions on Epidemiology and Prevention | Lifestyle and Cardiometabolic Health, held in New Orleans, LA.

Does age make a difference?

Prof. Qi and colleagues set out to investigate how antibiotic use at different times during adulthood, and for different durations, might be related to risk of death.

They studied data on antibiotic use from 37,510 women, aged 60 and older, in 2004–2012. The participants did not have heart disease or cancer at the start of the study.

The researchers found that taking antibiotics for at least 2 months in late adulthood was linked with a 27 percent increase in risk of death from all causes, compared with not taking them.

This link was stronger for women who also reported taking antibiotics during middle adulthood, or between the ages of 40 and 59.

Women who took antibiotics for 2 months or more were also at 58 percent higher risk of death due to heart problems, compared with women who did not use antibiotics. However, Prof. Qi's team found no association between antibiotic use and risk of death from cancer.

The researchers found that these associations were still strong even when factors such as lifestyle, diet, obesity, and use of other medications were taken into account.

Prof. Qi and colleagues point out that their research does not identify whether antibiotics contribute to cause of death — only that there is an association between long-term antibiotic use and risk of death.

As Prof. Qi concludes, "These results, however, contribute to a better understanding of risk factors for all-cause and cardiovascular death."

"We now have good evidence that people who take antibiotics for long periods during adulthood may be a high-risk group to target for risk-factor modification to prevent heart disease and death."