Readers who just scanned the headlines announcing the dramatic increase in CJD deaths in Great Britain might have had good reason to be alarmed. “CJD deaths ‘quadrupled since 1995′” the BBC headline read; CNN tagged their story with “Human form of mad cow disease on the increase.” But is the latest look at CJD rates in Great Britain really cause for alarm? Probably not.
To its credit, the BBC (unlike most other news reports), actually reproduced the data on CJD cases and deaths since 1994 which is reproduced in the table below:
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Year
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New CJD Diagnoses
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CJD
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First, the obvious thing to note is that the number of cases of CJD in Great Britain have remained relatively stable over the 5-year period of 1995-1999. The BBC spun this by saying that “the number of reportec cases of vCJD has increased by an average of 23% each year since 1994,” which is true, but this is the same as saying that on average over the past 5 years an average of 12.5 people are diagnosed with CJD each year.
Of course a prevalence rate of 13 or so people a year isn’t as compelling as CJD deaths quadrupling. Neither would it be much fun, if you’re a BBC reporter, to point out that in any disease where the number of new cases remains relatively constant, the total number of deaths will by definition at least quadruple over a 4-5 year period. Yet, I don’t remember the “Malaria Deaths Quadrupled” or “Cholera Deaths Quadrupled” stories, although in fact the number of total deaths from these diseases did quadruple over the period 1995-1999.
Second, the biggest problem with the statistics is it is very hard to put them into any sort of long-term context. Diagnosing CJD is a very time consuming and difficult business. According to the CNN report on the increase in cases and deaths, “The disease can only be confirmed by examining the brains of victims after they have died and scientists have only been able to establish the onset of infection by asking the victims’ relatives when symptoms first occurred.”
Since the Mad Cow scare started in the late 1990s, of course, physicians and others have been much more circumspect about such inquiries and examining the brains of suspected victims, but of course prior to the furor over the Mad Cow infection there was nowhere near the awareness about and throughness to uncover cases of CJD. As a result, it is extremely difficult to know whether the fact that there were no reported cases of CJD nor no reported deaths from CJD is a result of there simpy being no CJD or rather there being little or no effort to look for it (in fact there has been speculation that a considerable number of people who were diagnosed with alzheimer’s and alzheimer’s like diseases might instead have been misdiagnosed CJD sufferers).
CJD deaths ‘quadrupled since 1995’. The BBC, August 4, 2000.
Human form of mad cow disease on the increase. CNN. August 4, 2000