When I was a young doctor working in the countryside I contracted pneumonia. It took me a long time to recognize my main symptom – breathlessness – because I thought that symptoms were what patients, not doctors, had, and that therefore I could not myself have any. I therefore considered my feeling of being unwell to be an illusion. In the abstract I knew that doctors got ill and died, of course, but I found it difficult to believe this in practice, especially in my own case. When the symptom was severe enough, however, the penny dropped, and I looked at my own x-ray with something akin to pride.
Pneumonia, like almost all infectious diseases, is much less common now than it was then, but still remains a common enough cause of hospital admission and of death among the elderly. But according to a paper published in a recent edition of the New England Journal of Medicine, the annual cost of pneumonia requiring hospital treatment is $10 billion, a modest sum compared with the estimated costs of other diseases that one reads about in the same journal. Perhaps hospitals should try harder to raise their prices for treating pneumonia.
The paper is titled “Community-Acquired Pneumonia Requiring Hospitalization among U.S. Adults” – community being everywhere except the hospital, one of the commonest places to catch pneumonia. For eighteen months they enrolled all adults aged 18 and above whom physicians at five hospitals diagnosed as having pneumonia and needing to be admitted to the hospital. They then used a variety of diagnostic tests for bacterial and viral pathogens to be found in these patients, and compared them with a sample of patients attending one of the hospitals for non-respiratory problems.
By assuming that all patients in the hospitals’ catchment areas who needed hospitalization for pneumonia were admitted to the five hospitals and no others, they worked out the population rate of admission for hospitalization for pneumonia: 2.48 cases per year per thousand of population at risk. Assuming (what is almost certainly false) that having had pneumonia once does not mean increased susceptibility to having it again, the figure means than an adult has about a one in seven chance of being admitted to the hospital for pneumonia at some time in his life.
Unsurprisingly, the risk increased enormously with age. Between the ages of 50 and 64 you are 4 times more likely to need hospitalization for pneumonia than between the ages of 18 and 49, 9 times more likely between the ages of 65 and 79, and 25 times more likely after the age of 80. This makes me rather proud, the member of a small elite in fact, to have had pneumonia when I was only 27.
I was rather surprised by the frequency, or rather the infrequency, with which a causative organism for the pneumonia was found, and this after much more extensive testing than would normally be done on a patient with pneumonia. The investigators found evidence of at least one pathogenic organism in only 38 percent of cases: they found viruses in 27 percent of cases and bacteria in 14. Obviously, then, there were some patients with both.
One of the reasons for the low detection rate of bacterial pneumonia might have been that some of the patients had already been treated with antibiotics before they ever reached the hospital. The authors do not provide any information on this point, although such information might have been easy to gather. There are chemical and other causes of pneumonia, among them the aspiration of gastric contents. But still, the figure of 62 percent of indeterminate cause surprises me.
The triumph of medicine over infectious disease is perhaps the greatest of its achievements. But evidently there is still much to learn – as there always will be.
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