Medical researchers and statisticians have always had problems explaining the data for certain countries. Take Japan, for instance. The Japanese per capita consumption of cigarettes is among the highest in the world, yet Japanese life expectancy is also the highest (at least for larger countries). If the British results, which – if you remember – give non-smokers a ten-year edge over smokers, were applicable, Japanese women, 41% of whom smoke, could expect to live an extra four years on average. That would take them up to an incredible eighty-nine-year life expectancy. Overall life expectancy in Japan would exceed eighty-six, if both men and women didn’t smoke. And if we could rule out all the other risk factors, Japanese life expectancy would rise to well over 100 on the basis of table 2.
In the international smoking league tables, the first place goes to Greece, while Norway has the smallest per capita cigarette consumption in the developed world. Yet life expectancy in Norway is only three and a half months longer than in Greece, a country where physical exercise is famously unpopular and where hospital access is patchy – many islands don’t have hospitals at all.
What about high-fat diets and cholesterol intake? France is perhaps the most well-known paradox in this respect. Life expectancy in Metropolitan France is more than eighty years – the tenth highest in the international rankings – although the French diet is notoriously rich in fat. If we go into further detail, we find that deaths from cardiovascular disease are lower than in other nations (39.8 per 100,000 as opposed to 196.5 per 100,000 in the USA). In particular, Périgord, the region in south-west France famous for producing the high-cholesterol delicacy foie gras, has a particularly fatty diet, with plenty of butter, and duck and goose products. Yet life expectancy is higher than in the rest of France and cardiovascular death rates even lower. Back on the national scale, if we compare France to Norway, we find that per capita cigarette consumption is 2.8 times higher in the former, and fat intake significantly lower in the latter. But – you guessed it – the French live on average about a year longer than Norwegians. The only possible conclusion is that there must be factors other than smoking and cholesterol to explain the difference in life expectancy between France (and in particular Périgord) and the USA, Norway, or many other developed nations, where public health campaigns against these two “vices” have had more effect.
By focusing entirely on the negative aspects of the risk factors – and the worst-case scenarios at that – these public health campaigns tend to raise falsely positive expectations about how we individuals can improve our chances of living longer. The message may be that “doctor knows best.” But the deeper we dig into the evidence, the most charitable interpretation is the “doctor is telling us to be on the safe side.” And, strangely, there’s been comparatively little medical research about why the Japanese, Greeks, and French live longer than medical research suggests they ought to. If we’re going to make reasoned choices about how to live our lives, we need more objective and accurate cost-benefit analyses of the many different activities that influence longevity.
© Spyros Makridakis, Robin Hogarth and Anil Gaba, 2009