How Long Does a Cough Last? Comparing Patients’ Expectations With Data From a Systematic Review of the Literature

To the editor:
This is a significant paper describing a well-designed study investigating evidence and expectations regarding the duration of "acute cough illness" (ACI).[1] It actually describes two sub-studies, one a random digit dial telephone survey carried out in the U.S. state of Georgia, the other a systematic review of literature regarding the duration of ACI. The main reported finding is that there "is a mismatch between patients' expectations regarding the duration of ACI and the actual duration based on the best available evidence." The authors suggest that this "mismatch" may be a factor contributing to inappropriate antibiotics prescriptions for ACI.

This is all quite reasonable, and this paper is clearly an important contribution to the literature. Nevertheless, there are limitations, alternative interpretations, and unresolved questions deserving of consideration. Let us begin with two quotes from Arthur Kleinman: A) "Modern physicians diagnose and treat diseases (abnormalities in the structure and function of body organs and systems), whereas patients suffer illnesses (experiences of disvalued changes in states of being and in social function; the human experience of sickness);"[2] and B) "Two levels of academic endeavor in primary care should develop if family medicine and the other primary care disciplines are to become viable academic enterprises: (1) practical applied studies of discrete salient health care problems ... and (2) concepts, theoretical models and research approaches that can contribute to a unique scholarly discourse on primary care and that can provide the intellectual foundation for self-contained research programs which together create a science of clinical medicine."[3]

Where better to focus attention than acute illness characterized by cough? Cough is a discrete salient health problem experienced by patients and investigated by scientists. Cough has a central place in the theoretical and applied science of acute respiratory infection. So, what exactly is "acute cough illness," and how long do ACI episodes last? The search strategy used by these authors focuses on acute infectious reasons for cough, with "bronchitis," "respiratory infection," and "chest cold," as inclusion terms, and "asthma," "allergies," "sinusitis," "pneumonia," and "chronic lung disease" as exclusions. Identified studies shown in their Table 1 include adults and older children typically described as having "bronchitis" or "productive cough."

While the people in these published studies may be similar to many of the patients who present in clinic with prolonged productive cough, they may not represent all people having acute illness with cough. It might be that people whose coughs are more severe or last longer are more likely to seek medical care (and to enter bronchitis studies) than the general population of people experiencing coughing illness. Additionally, there may be other factors to consider. A study of resource use and ACI costs in 13 European countries found wide variation in antibiotic prescribing.[4] Health systems specifics, including incentivized compensation plans and availability of advanced diagnostic testing, were implicated, along with general medical culture and practice.

To shed some light on the issue of cough duration, we looked at our own database of n=1,194 people who participated in four studies in Madison, Wisconsin, over the past decade.[5-8] To be enrolled in these studies participants had to have a Jackson score of 2 or more,[9] an acute nasal and/or throat symptom arising in the previous 48 hours, and state that they "have a cold" or "are coming down with a cold." Two of these studies were observational, designed to test the WURSS questionnaire.[5-6] Two were randomized trials, testing echinacea, placebo, doctor-patient interaction, meditation, and exercise.[7-8,10-11] As most of the interventions tested did not lead to clearly demonstrable effects, we feel that these data can be used to investigate the natural course of acute respiratory infection. Only the meditation group in the latest (and smallest) of these studies[8] showed statistical significance when compared to randomized control.

The figure portrayed here [annfammed.org/site/misc/TRACK/BarrettFigure.doc] suggests that the vast majority of people with colds also have cough, and that most colds and most coughs resolve within 2 weeks of onset. Of the 915 people who reported cough the day after enrollment, only 136 (15%) were still sick with a cough 2 weeks later. Median cough duration falls between day 8, when 503 still coughed, and day 9, when only 426 reported coughing. Unfortunately, most of our studies followed people only to a maximum of 14 days, complicating the calculation of mean duration. The meditation and exercise study,[8] however, followed people up to 21 days, and found that of 93 colds, 67 had cough on the 1st day, but that only 6 of these people still had a cough 3 weeks later.

On face value, our data seem more consistent with expectations assessed in the Georgia telephone poll (5 to 9 day ACI duration) than with literature data summarized by Ebell et al. (mean 17.8 days of ACI).[1] There are several ways to explain these discrepancies. Different people in different places have different health behaviors and risks, and are exposed to different varieties of pathogens at different times of the year. Various studies use varying methods to enroll people and to monitor symptoms, employing a variety of definitions, cutoffs and analytic methods. Our own studies took in people with early colds, many of them quite mild. Cough was common, but not required. Very few reported fever and productive cough. The Georgia poll first asked people to "Suppose that you get sick and the main symptom is a cough" and that they were "coughing up yellow mucus and have a slight fever (100.5 degrees)," and then asked them to prognosticate on the duration of illness. Published bronchitis studies enrolled people with more severe and prolonged illness, but did not ask about expectations. We have asked participants to predict duration and severity of acute respiratory illness, and found no evidence they could beat chance in doing so.[12] As far as we can tell, no study to date has been specifically designed to investigate ACI duration as the primary outcome.

Which brings us back to Kleinman. Three decades have gone by since those words were published. In the interim there have been important advances in knowledge relevant to family medicine and primary care, with numerous "practical applied studies of discrete salient health care problems." There has been some progress toward "theoretical models and research approaches that can contribute to a unique scholarly discourse." One of the greatest achievements has been the movement from a disease- oriented paradigm to one seeking to understand and redress human illness. Landmarks include introduction of the biopsychosocial model,[13] the call for patient-oriented evidence that matters (POEMs),[14] and the increasing use of symptomatic and functional assessments as primary outcomes in clinical trials.[15]

And yet we are left with huge gaps in both knowledge and method. Data available to answer the basic question "How long does a cough last?" are rudimentary at best. Few of the studies available are large enough to adequate statistical power, and none were designed to be representative of a population. The largest prospective cohort studies were done decades ago,[16-19] before PCD-based viral identification and advanced computerized statistical methods were widely available. These early studies (which seem to have eluded the scrutiny of Drs. Ebell et al.) did examine natural course of illness, but did very little in the way of investigating determinants and mediators. As for treatment effectiveness, apart from the fact that antibiotics are at most marginally efficacacious,[20] we know very little. The most common cough suppressants, such as dextromethorphan, codeine, and benzonatate, have not been tested in large, well-designed randomized trials.[21] In summary, it must be concluded that we lack the most basic knowledge regarding the natural course and treatment effectiveness of ACI. Perhaps even more problematic is the failure to develop appropriate theory and methods to reconcile evidence and perspectives related to patient-oriented illness and scientific disease frameworks of knowledge.

There is little doubt that experiencing the symptoms of acute coughing illness can have a profound impact on one's quality of life. Among other things, ACI can interrupt sleep, cause one's body to ache, and interfere with any of a number of daily life activities. Life during acute coughing illness can be miserable indeed. It may be that some people are overly optimistic regarding the duration of ACI, and that more realistic expectations might reduce both clinic visits and antibiotic prescriptions. Clearly, there is much to be learned about the nature of ACI, including the duration and severity among various populations and sub-classes of illness. Methodologies and paradigms taking account of both popular and professional perspectives will be needed to build a sound intellectual foundation towards a valid science of clinical medicine.

Reference List
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Competing interests:   None declared