A massive study of 12 169 men rehabilitating after myocardial infarction, coronary bypass surgery, or ischaemic heart disease found the best prognostic indicator was the volume of oxygen taken up during maximum exercise (Circulation2002;106:6-21). This measure of cardiovascular fitness may be improved by taking exercise, and the authors conclude that “even a small exercise induced gain in aerobic power should greatly improve both functional capacity and the prospects for survival.”

Screening for lung cancer is controversial, partly because of the paradox that as more cases are detected the mortality from the disease either remains static or actually falls (Chest2002;122:328-37). Earlier diagnosis improves survival (the percentage of patients alive five years after diagnosis), but mortality may actually rise because the screening procedure is not without risk. The fundamental problem is that 30 doublings of the tumour mass are required before the tumour achieves a diameter of 1 cm (the threshold for radiological diagnosis), and few of the cancers that are detected are curable.

In the United States between 1980 and 2000 infant mortality in white babies fell from 10.9 to 5.7 per 1000 …