Monday, April 25, 2011

More Spirit Level confusion

Here is a line in Kate Pickett and Richard Wilkinson's The Spirit Level: Why Equality is Better for Everyone, arguing that following the decline of infectious diseases in the 20th century:

...we are left with the so-called diseases of affluence - the degenerative cardiovascular diseases and cancers.

Later they explain this:

As we described in Chapter I, when infectious diseases lost their hold as the major causes of death, the industrialized world underwent a shift, known as the 'epidemiological transition', and chronic diseases, such as heart disease and cancer, replaced infections as the major causes of death and poor health.

This is a little unclear because it does not explain whether or not cancer and heart disease are caused by modern affluence. Dan Gardner's Risk: The Science and Politics of Fear describes multiple examples of confusion over this very thing, explaining that declines in infectious disease lethality simply left more survivors to get cancer. Gardner gives the example of Canadian biologist David Suzuki, who argued that industrial chemicals were increasing cancer rates to the point where cancer had surpassed heart disease as Canada's 'number one killer':

But it is not true, as Suzuki seems to assume, that cancer's rise to leading killing means cancer is killing more people. It is possible that heart disease is killing fewer people. And that turns out to be the correct explanation. Statistics Canada reported that the death rates of both cardiovascular disease and cancer are falling but 'much more so for cardiovascular disease'.

Risk of developing cancer soars as individuals get older. As a result, rising deaths from cancer could actually indicate massive improvements in health, as more young people manage to survive into old age. A World Health Organisation comment that 'Deaths from cancer worldwide are projected to continue to rise to over 11 million in 2030' could actually imply global improvements in health.

We can compare a developing country with a richer developed country for an example. In 2009, the leading causes of death for males in England and Wales were as follows:

1) Ischaemic heart diseases 17.4%
2) Malignant neoplasm (cancer) of trachea, bronchus and lung 7.2%
3) Cerebrovascular diseases 7.1%

Comparing this with male deaths in South Africa we see that cancer drops way down the list:

1) HIV/AIDS 23.5%
2) Interpersonal violence 8.4%
3) Tuberculosis 6.8%
...13) Trachea, bronchus and lung cancer 1.7%

Someone could observe that lung cancer is the thirteenth highest cause of death for men in South Africa, but the second highest cause in England and Wales, and guess that Britons face greater danger from cancer than South Africans do. But the truth is that England and Wales are protected from TB, violence, AIDS and a range of other causes of death. In South Africa many people never get the chance to age long enough to develop cancer or heart disease.

So The Spirit Level's description of a 'shift' of risk from infectious disease to cancer and heart disease seems a little unclear. Rather than a shift there was a decisive decline in many lethal diseases, letting people grow old enough to develop other ailments. That's a 'shift' we should celebrate.

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