Saturday, April 17, 2010

William Farr- the inventor of medical statistics?

In 1858, a British epidemiologist named William Farr set out to study what he called the “conjugal condition” of the people of France. He divided the adult population into three distinct categories: the “married,” consisting of husbands and wives; the “celibate,” defined as the bachelors and spinsters who had never married; and finally the “widowed,” those who had experienced the death of a spouse. Using birth, death and marriage records, Farr analyzed the relative mortality rates of the three groups at various ages. The work, a groundbreaking study that helped establish the field of medical statistics, showed that the unmarried died from disease “in undue proportion” to their married counterparts. And the widowed, Farr found, fared worst of all.

Farr’s was among the first scholarly works to suggest that there is a health advantage to marriage and to identify marital loss as a significant risk factor for poor health. Married people, the data seemed to show, lived longer, healthier lives. “Marriage is a healthy estate,” Farr concluded. “The single individual is more likely to be wrecked on his voyage than the lives joined together in matrimony.”

While Farr’s own study is no longer relevant to the social realities of today’s world — his three categories exclude couples living together, gay couples and the divorced, for instance — his overarching finding about the health benefits of marriage seems to have stood the test of time. Critics, of course, have rightly cautioned about the risk of conflating correlation with causation. (Better health among the married sometimes simply reflects the fact that healthy people are more likely to get married in the first place.) But in the 150 years since Farr’s work, scientists have continued to document the “marriage advantage”: the fact that married people, on average, appear to be healthier and live longer than unmarried people.

via NYT

The following bit about him was also interesting;

There was a major outbreak of cholera in London in 1849 which killed around 15000 people. Early industrialisation had made London the most populous city in the World at the time, and the River Thames was heavily polluted with untreated sewage. Farr subscribed to the conventional theory that cholera was carried by polluted air rather than water - the miasmic theory.

As a result of studying this outbreak, the physician John Snow proposed what is now known to be the actual mechanism for transmission - that people were infected by swallowing something and that it multiplied in the intestines.

There was another epidemic in 1853, and Farr gathered statistical evidence to try to support the miasmic theory. He demonstrated statistically that cholera was spread by polluted air by showing that the likelihood of dying of the disease was linked to the height that the victims lived above the River Thames. He interpreted this as support for the miasmic theory - the air at lower altitudes being dirtier. However he also obtained details of where different water companies drew their water, and generated statistics on the number of deaths per water company. He discovered that people supplied with water from two companies in particular- the Southwark & Vauxhall and the Lambeth water companies - which drew their water directly from the Thames were particularly likely to suffer. Although he did not agree with Snow's waterborne theory, he gave him a great deal of help in collecting data to support it; in particular by providing the addresses of people who had died.

There was a further epidemic in 1866, by which time Snow had died. Farr had by now come around to believe Snow's explanation. He produced a monograph which showed that mortality was extremely high for people who drew their water from the Old Ford Reservoir in East London.

We recommend the The Ghost Map by Steven Johnson

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