Underestimating cough duration may skew antibiotic perceptions

By Caroline Price, Senior medwireNews Reporter

US researchers suggest that one reason patients request antibiotics for respiratory infections is that they greatly underestimate how long it usually takes for acute cough illness to resolve.

According to their study, patients believe an acute cough should only last around 7-9 days, whereas published evidence on the natural history of acute cough illness suggests the usual duration is at least twice that, at around 18 days.

Writing in the Annals of Family Medicine, the authors reason that better informing patients about how long it can take for a cough to clear up could help to reduce inappropriate antibiotic use.

"If a patient expects that an episode of acute cough illness should last about 6 or 7 days, it makes sense that they might seek care… and request an antibiotic after 5 or 6 days," write Mark Ebell and colleagues from the University of Georgia in Athens.

"Furthermore, if they begin taking an antibiotic 7 days after the onset of symptoms, they may begin to feel better 3 or 4 days later, with the episode fully resolving 10 days later. Although this outcome may reinforce the mistaken idea that the antibiotic worked, it is merely a reflection of the natural history of acute cough illness."

Ebell and colleagues conducted a systematic review of observational studies and placebo/control groups of randomized clinical trials to determine the average duration of undifferentiated acute cough illness. This covered acute bronchitis, but excluded cases with a suspected cause of cough, such as influenza, pneumonia, sinusitis or anthrax.

Analysis of the 19 eligible studies revealed that the mean duration of any cough was 17.8 days, with a range of 15.3 to 28.6 days. Between 86% and 95% of patients still had cough at 8 days after onset in three studies reporting this outcome, while the percentage with cough at the end of the study was 91% at 16 days in one study, 73% at 17 days in a second, and 82% at 21 days in a third.

To assess patient reports of cough duration, the team surveyed 1131 people from the state of Georgia, of whom 493 responded. Among the 395 who responded specifically to the question on expected duration of cough, the median estimate was 5 to 7 days, and the mean 7.2 to 9.3 days, depending on the scenario. People tended to ascribe a longer duration of illness to episodes characterized by green sputum rather than yellow sputum or dry cough (8.7 vs 7.6 days).

Analysis showed that nonWhite respondents, those with no more than college education, and those who had previously been given antibiotics for an acute cough were all around twice as likely as their counterparts to believe that antibiotics are "always helpful."

"We believe that education of the general public, the media and physicians should emphasize appropriate expectations regarding the natural history of acute cough illness in order to reduce inappropriate demands for antibiotics," the authors conclude.

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