Patients with newly diagnosed comorbidities, such as chronic obstructive pulmonary disease (COPD), heart failure, or asthma, had an increase in rates of antibiotic prescribing in the months prior to their diagnosis, U.K. researchers found.
In the 1 to 3 months prior to diagnosis, rates of antibiotic prescribing increased at least two-fold for both COPD and heart failure, and were up 88% for asthma, reported Laura Shallcross, PhD, of University College London, and colleagues in Clinical Infectious Diseases.
They noted that patients with comorbidities are at higher risk of developing antibiotic resistance compared with healthy patients because of “their increased vulnerability to infection, frequent antibiotic exposure, and contact with secondary care where drug-resistant infections are prevalent.” Notably, diabetes, chronic lung, kidney, or vascular disease may increase a patient’s susceptibility to bacterial infection or increase their risk of infection-related adverse outcomes, they said.
Researchers examined data from the Clinical Practice Research Datalink, a primary care database of U.K. patient records, from January 2008 to December 2015. They looked at monthly rates of antibiotic prescribing before and after diagnosis of several comorbidities and compared those to a group of control patients without comorbidities.
Comorbidities were included that were “previously listed in national guidance” as those that were relevant to a doctor prescribing an antibiotic, including:
- Heart failure
- Peripheral artery disease (PAD)
Overall, about a million patients were eligible for inclusion in the study. They were an average age of about 49 and about 52% of patients were women. There were 106,540 patients who were newly diagnosed with one of the included comorbidities, with the most common new diagnosis being diabetes (2.7%). In addition, 106,540 patients were selected as matched controls based on age at index, sex, and month of index diagnosis.
The authors reported that 1 to 3 months prior to diagnosis, there was a 2.3-fold increase in antibiotic prescribing versus baseline prior to COPD diagnosis (RR 2.28, 95% CI 2.17-2.39), a two-fold increase for patients with heart failure (2.03, 95% CI 1.83-2.26) and an 88% increase prior to asthma diagnosis (RR 1.88, 95% CI 1.79-1.96).
But the authors noted that after diagnosis, rates of antibiotic prescribing for patients diagnosed with COPD and heart failure were down to 42% and 32% above baseline, respectively, while asthma patients returned to baseline levels immediately after diagnosis.
Patients with diabetes experienced a 55% increase in the rate of antibiotic prescribing versus baseline at 1 to 3 months prior to diagnosis (RR 1.55, 95% CI 1.48-1.61). They also stated that rates of prescribing increased by 34% among patients with new-onset PAD (RR 1.34, 95% CI 1.16-1.54). Interestingly, rates of antibiotic prescribing remained high following diagnosis of stroke, coronary heart disease, and PAD, with a 30% to 39% increased rate of prescribing versus baseline 12 months after diagnosis.
Examining control patients, the authors noted that baseline rates of antibiotic prescribing were up to 43% lower in controls versus comorbid patients.
They offered a hypothesis for their findings, writing that “this pattern of prescribing is likely to be driven by difficulties in distinguishing first presentation of asthma, heart failure and COPD from respiratory tract infections in primary care.”
But they added that another explanation could be that repeat infections could trigger the onset of specific chronic diseases. While there is evidence of viral infections linked to acute events such as myocardial infarction and encephalitis, the evidence for bacterial infections is less clear, they said. However, they suggested that “a rapid increase in frequency of antibiotic prescribing may be a useful warning sign for the onset of chronic disease.”
Study limitations included its observational nature, and that the authors only examined antibiotic prescribing in a primary care, not a hospital, setting and did not include comorbidities such as cancer or rheumatological conditions that might influence a patient’s susceptibility to infection.
“Onset of respiratory symptoms may be misdiagnosed as respiratory tract infection. Earlier diagnosis and treatment for these comorbidities in primary care represents an opportunity to reduce unnecessary antibiotic prescribing for these patients,” they concluded.
The study was supported by the U.K. Economic and Social Research Council.
Shallcross disclosed support from a National Institute of Health (NIHR) Research Clinician Scientist Award grant. A co-author disclosed support from a NIHR Senior Investigator award.