For a change it was nice to read good news (Fewer people developing dementia, says study, 20 April). Carol Brayne says “physical health and brain health are clearly highly linked” but only suggests at the nature of the link. The idea seems to be that for some reason men working independently of each other to improve their lifestyles over a number of years were acting in sufficient numbers to have a significant impact on the data as a whole. This seems somewhat surprising. However, there may be a more passive factor at work that correlates with the period of the study, 1990-2013. During the first part of this period the use of leaded petrol in cars was steadily being reduced, leading to a ban in 1998. The detrimental effect of lead in the environment on the developing brains of young people was well documented. Perhaps its long-term effect on the brains of older people was simply overlooked.
Ray Perham
Ilford, Essex
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