Posts Tagged ‘Epidemiology’

No mask needed, just don’t breathe

August 25, 2020

There are some who believe that epidemiology is a science. Others believe it is an art and yet others that it is the study of social behaviour based on gut-feel and science.

Whatever it is, it is not settled science.

An enveloped virus such as the Wuhan virus can survive for up to 2 months in a refrigerated corpse.

In studies looking at how bird flu (avian influenza virus, an enveloped virus) survives in chicken carcasses, 90% of the virus was inactivated in around 15 days when the carcass was left at room temperature. But if the carcass was held at refrigerator temperatures (4C/40F), the virus lasted 4.5 times longer—that’s more than two months.


Epidemiology is still more art than science and sometimes just speculation

July 24, 2020

The Wuhan virus, after 6 months, is still not under control.

I have grown a little tired of being told by all kinds of people that they are just following the science in the fight against the Wuhan virus. What science? There is a widespread delusion that epidemiology is a “settled science”. Epidemiology is, in reality, a mix of science and art and of “social science” (which is always a politicized view of behaviour). It is about “the frequency and pattern of health events in a population”. With a little known virus, as in this case, epidemiology relies on models and speculation. When the speculation is garbage, the model results are also, necessarily, garbage. The model results have ranged from the ridiculously complacent to the grotesquely alarmist, but what they all have in common is that they are/were wrong. Nothing surprising in that. That is the nature of modelling. A mathematical model is nothing more than a crystal ball and model results are always forecasts of the future. The problem lies in the delusion that epidemiology is an exact science and that model results give a sound and certain basis for public policy.

In the absence of a vaccine we are being led (or misled) by politicians blindly following the epidemiologists’ speculations about both the characteristics of the unknown virus and about social behaviour. In the space of 4 months the “best” epidemiologists at the WHO have changed their view of the Wuhan virus from being “non communicable between humans”, to “communicable by liquid droplets between humans”, to now be of “air borne transmission”. The experts have been divided whether transmission is from the symptomatic or from the asymptomatic. There are as many speculative views about when herd immunity can be achieved as there are epidemiologists. No one really knows. Art not science. Herds are always moving and herd immunity depends upon leaving the weak behind. Public policy is floundering as it staggers from lockdowns to no lockdowns to social distancing, from masks to no masks to some masks to masks for some, and from testing those with symptoms to restricted testing to mass testing. There is no certainty about whether testing is to be for the virus or for antibodies to the virus.

The Center for Disease Control has this definition of epidemiology:

Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.

But then they go on:

…. the practice of epidemiology is both a science and an art.

The reliance on speculation and the resulting weaknesses of epidemiology are well known and there are many scientific articles about spurious but statistically significant epidemiological forecasts. This article in the BMJ from 2004 is just an example.

The scandal of poor epidemiological research

Something surely must be wrong with epidemiology when the new editors of a leading journal in the field entitle their inaugural offering, “Epidemiology—is it time to call it a day?” Observational epidemiology has not had a good press in recent years. Conflicting results from epidemiological studies of the risks of daily life, such as coffee, hair dye, or hormones, are frequently and eagerly reported in the popular press, providing a constant source of anxiety for the public.  In many cases deeply held beliefs, given credibility by numerous observational studies over long periods of time, are challenged only when contradicted by randomised trials. In the most recent example, a Cochrane review of randomised trials shows that antioxidant vitamins do not prevent gastrointestinal cancer and may even increase all cause mortality. 
Now Pocock et al describe the quality and the litany of problems of 73 epidemiological studies published in January 2001 in general medical and specialist journals. …… Worryingly, Pocock et al find that the rationale behind the choice of confounders is usually unclear, and that the extent of adjustment varies greatly. They also confirm that observational studies often consider several exposures, outcomes, and subgroups. This results in multiple statistical tests of hypotheses and a high probability of finding associations that are statistically significant but spurious. 

Modern epidemiology starting from – say – the 1854 London cholera outbreak has vastly improved public health. But it is not just a science and it is certainly not a “settled science”. The Wuhan virus is not under control. The various public policy interventions (lockdowns of various kinds and the deselection of the old for treatment) have prolonged, rather than shortened, the outbreak. The lockdowns may have protected health systems while maximizing the number of deaths. In fact, politicians have often abdicated responsibility for public policy to epidemiologists and bureaucrats who have not been best-suited to make political decisions. In other cases public policy has exploited epidemiology to protect the system rather than protecting people.

This is not so much to criticize epidemiology as to criticize the manner in which public policy has misused epidemiology. Epidemiology can only be an input for determining public policy. It cannot replace common sense. And it is not a convenient shelter for politicians to hide behind.


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