20 Oct 2014

What the group can tell us about our health

Epidemiology can’t predict an individual’s health prospects but it is a powerful tool to assess risk. Adam Jenney reviews a new book that celebrates this under-appreciated branch of medicine.

Enigmas of health and disease: How epidemiology helps unravel scientific mysteries
Alfredo Morabia
Columbia University Press (2014), RRP $30.00

Telling a patient they have a serious illness is one of the challenges of clinical practice. And it is even harder to answer the question that is invariably asked when the news sinks in: “What happens now?”

It is impossible to know exactly. Everyone is different and there is no crystal ball. But, as Alfredo Morabia elegantly explains, epidemiology makes a good fist of it as long as we think in terms of groups, not individuals. By comparing groups with certain risk factors or conditions, epidemiologists demonstrate a truth for that group. This can go a long way to answering a patient’s questions without predicting that individual’s future. It allows a sensible discussion about risk, life expectancy and the chance of cure. 

Morabia is a medical graduate from Switzerland who works as an academic epidemiologist in New York. This book is aimed at a general audience, but there’s plenty here for medical experts too. He describes historical triumphs in epidemiology on a broad canvas and tells some fascinating stories. 

In London, John Snow linked a cholera outbreak in 1854 to a particular water pump through rigorous data collection. In mid-19th century Vienna, Ignaz Semmelweis saved the lives of many mothers by making doctors wash their hands before delivering babies. 

Is epidemiology art, science, medicine or maths?

Morabia succinctly explains Richard Doll and Austin Bradford Hill’s breakthrough when, in the 1950s, they were set the task of showing tobacco smoking causes lung cancer. They pointed out that the number of non-smokers diagnosed with lung cancer (2.1 per 100,000) was tiny when compared to the incidence of lung cancer in smokers (17 per 100,000). While most smokers won’t get lung cancer it is impossible to tell which individuals will succumb; epidemiology was able to demonstrate at a population level that smoking causes cancer. 

The map of Soho in London by John Snow showing the clusters of cholera cases in the epidemic of 1854. We've coloured the map to help make the clusters stand out. Meticulous work led Snow to identify one water pump in Broad Street (centre of the map) as responsible for spreading the disease.

Morabia is not afraid to show when his subject lets us down. He admits epidemiology can be used for nefarious purposes (eugenics) and manipulated by zealots (high dose vitamins). He draws his subject matter from both the anglophone and non-English speaking worlds, which gives a richness to his thesis without labouring any particular point.

So what is the purpose of the book? Certainly it informs and entertains. Is epidemiology art, science, medicine or maths? I don’t believe Morabia cares. He loves what he does, writes like an historian with an eye to humanistic philosophy, but is always faithful to the science. He is passionate about his subject and wants to share it. 

Until now epidemiology has largely been kept hidden in the universities. Morabia wants it taught in schools everywhere – and now so do I. And probably the best way to start the education process is with this book.

Adam Jenney is an infectious disease physician and clinical microbiologist.