Jellyfish stings and other stories . . .

Across all the centuries that Minerva can remember, adults have worried that children of the next generation will be soft and unfit for the rigours of life. The latest expression of this Spartan anxiety comes in a study of resting pulse rates in 9-11 year old children in the UK between 1980 and 2008 (Arch Dis Child 2013, doi:10.1136/archdischild-2013-304699). There has been a tiny but steady drift upwards in the mean resting pulse of children of both sexes over this period, much amplified by the scale of the graphs in this paper. Only a small part of this is attributable to obesity, so the authors conclude that the rest is probably the result of reduced physical activity.

But at the other end of the human life cycle, there is some good news. A histological study of brains from elderly people shows that amyloid deposition decreased by 24% from 1972 to 2006 (Neurology 2013, doi:10.1212/WNL.0000000000000069). This matches other evidence that …