David Owen argues that Joe Biden and Donald Trump are both too old to be president

SOME PARTS of most people’s brains that are involved in higher cognitive thinking are subject to an ageing process starting from 60-70 years of age and continuing until death. In particular, there is a shrinkage of the brain’s frontal lobe and, deeper in, of an area called the hippocampus. The brain’s surface areas can also thin and nerve fibres shrink, which slows the way the brain processes information. Among the chemical changes that researchers think occur during brain ageing are a decrease of neurotransmitters, particularly dopamine, serotonin and acetylcholine, in parts of the brain.