New research finds that, for women over 60, there's a link between long-term use of antibiotics and heightened odds for heart-linked death.
But the study of more than 37,000 U.S. women couldn't prove that the bacteria-fighting meds were the cause of the troubling trend, or whether the culprits were the illnesses the antibiotics were intended to fight.
"It isn't yet clear whether long-term antibiotic use is the specific cause of the association -- for example, women who reported antibiotic use might be sicker in other unmeasured ways," said lead researcher Dr. Lu Qi, a professor of epidemiology at Tulane University in New Orleans.
The study of women age 60 or older found those who took antibiotics for at least two months were 27 percent more likely to die from all causes over a period of eight years, and they had a 58 percent greater risk of dying from heart disease, specifically.
This was true even after the researchers considered other traditional risk factors, such as diet, obesity and the use of other medications.
But did the antibiotics themselves hike the risk?
It's possible, Qi's group said, because prior studies have shown that antibiotics can lead to chronic changes in the composition of bacteria living in the human gut, or "microbiota."
"Gut microbiota alterations have been associated with a variety of life-threatening disorders, such as cardiovascular diseases and certain types of cancer," Qi said in an American Heart Association news release.
"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."
The women in the study were divided into four groups based on their use of antibiotics: Those who never took them; those who were on them for less than 15 days; those who were on them for between 15 days and two months; those who were taking the drugs for two months or more. The researchers monitored the women from 2004 to 2012.
The link between antibiotic use and increased risk of death was more notable among the women who also reported using antibiotics earlier in life, from the age of 40 to 59, than those who didn't take the drugs when they were middle-aged, the study showed.
However, two heart specialists were leery of casting the blame on antibiotics.
"If any patient requires antibiotics for two months or more out of the year, they are inherently a sicker and more fragile population," said Dr. Rachel Bond. She helps direct Women's Heart Health at Lenox Hill Hospital in New York City.
Bond said that it's therefore "not surprising" that women who are sicker might also have frailer hearts.
Dr. Cindy Grines is chair of cardiology at Long Island Jewish Medical Center in New Hyde Park, N.Y. She agreed with Qi that "there have been numerous warnings about certain antibiotics being associated with sudden cardiac death due to arrhythmia -- erratic heart beats."
Therefore, "I personally tell my cardiac patients not to use antibiotics for mild to moderate infections such as bronchitis or sinusitis."
But Grines added that the risk to the heart typically occurs while the patient is taking the drug -- not years later, as was seen in the new study.
So, like, Bond, Grines suggests that "the prolonged antibiotics were given for a serious medical condition that ultimately contributed to the patient dying 20 years later."
The findings were to be presented on Thursday at an American Heart Association meeting in New Orleans. Findings presented at medical meetings are typically considered preliminary until published in a peer-reviewed journal.
The U.S. National Heart, Lung, and Blood Institute provides more information on risk factors for heart disease.
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