It found that nearly half of antibiotic prescriptions written for Ontario seniors in long-term care in 2010 were for treatment courses longer than seven days, which in most cases would be unnecessarily lengthy.
The prescribing habits of doctors rather than the needs of the patients appeared to be what was behind the longer-than-needed use of the drugs, the study also found.
"We're all creatures of habit in life, and more likely to do something the same way as we did previously," said Dr. Nick Daneman, first author of the paper, published Monday in the journal JAMA Internal Medicine.
"So if we get used to prescribing 14 days, we're more likely to be writing 14 days on most of our antibiotic prescriptions. If we get used to writing five days, we're more likely to write that on future prescriptions as well."
Daneman is an adjunct scientist at Toronto's Institute for Clinical Evaluative Sciences; his co-authors are also affiliated with the institute. Daneman is an infectious diseases specialist at Sunnybrook Health Sciences Centre in Toronto as well.
Antibiotic use is common among seniors, whose waning immune systems leave them susceptible to infections. In long-term care, antibiotics are most commonly used to treat urinary tract or respiratory tracts infections, or infections of the skin and soft tissue. Most of these infections can generally be treated successfully with seven or fewer days on antibiotics.
In this study, the researchers looked at records for Ontario seniors living in long-term care in 2010. They found nearly 78 per cent of residents of these facilities had at least one prescription for an antibiotic during the study period. And while seven days was the most common length of treatment course, 45 per cent of prescriptions were for longer than that.
"You don't need to treat for more than seven days for most of these infections. And yet what they found was even if you assume that all of the courses of antibiotics were appropriately decided upon, the duration was still inappropriately prolonged," said Dr. Andrew Simor, an infectious diseases expert who was not involved in the study.
Simor said some doctors may be trying to play it safe. "They often will say: 'We'll treat until they get better and then maybe a couple of extra days just to be sure.'"
But in fact, using antibiotics for longer than is needed isn't playing it safe. These drugs have side-effects. There's a greater risk of developing C. difficile diarrhea or of contracting an infection caused by an antibiotic resistant bacterium the longer a senior takes antibiotics.
Likewise, excessive use of these drugs in long-term care facilities contributes to the overall pressure antibiotic use places on bacteria, fuelling the development of so-called superbugs. Antibiotics typically kill susceptible bacterial strains, giving those that are naturally resistant to the drugs a chance to thrive and multiple.
"So there's no question that this is an issue that profoundly affects not only the community at large, but the individual who is being prescribed an inappropriately long course of antibiotics as well," said Simor, who is head of microbiology at Sunnybrook Health Sciences Centre.
Daneman and his co-authors tried to determine whether differences in the patients could account for the longer prescriptions. Maybe the patients who received antibiotics for 10 or 14 days were sicker or sick with different conditions? But they found that couldn't explain the differences.
They concluded it was an issue of individual prescribing patterns, with individual doctors generally prone to ordering short, average or long duration courses of antibiotics.
Interestingly, when doctors who wrote long antibiotic prescriptions were compared to those who wrote short and average-length ones, there were no clear demographic differences among the three groups. One couldn't predict, say, that male doctors would prescribe one way and females another. Nor did they break down by age, years in practice, or whether the doctor was trained in Canada or abroad.
The study suggests that if all doctors adopted the habits of those who treat with short courses of antibiotics, the overall number of days seniors in long-term care end up on antibiotics could drop by as much as 19 per cent.
Daneman said he thinks this is an exciting opportunity, an way to reduce the overall use of antibiotics that is within reach.
"It's easy to talk about and difficult to do, antibiotic stewardship," he said, referring to the term used to describe efforts to use the drugs wisely to protect their efficacy. Rates of resistance are rising at alarming rates in some bacterial diseases, raising the spectre of a return to a time when some infections might be untreatable.
"Shortening that tail end of treatment, at which point antibiotics are putting people at potential risk without any potential benefit, seems to be a real feasible way to reduce antibiotic overuse," Daneman said.
But Simor suggested changing this behaviour may not be easy.
Dementia is common among seniors in long-term care. So doctors may be trying to treat patients who cannot describe their symptoms, which complicates their care. As well, long-term care facilities don't typically have testing laboratories and pharmacists, which offer key support to hospitals struggling to reduce inappropriate use of antibiotics.
Said Simor: "All of this contributes to enormous diagnostic uncertainty that may drive inappropriate antibiotic use. And it's a real challenge.''