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

SOME PARTSMP of most people’s brains that are involved in higher cognitive thinking are subject to an 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.I was a neurologist, a doctor of medicine who specialises in the brain, and a research fellow at St Thomas’s hospital, across the Thames from Britain’s House of Commons, before I became a Labour in 1966. I continued to do medical research after going into politics as the Commons in those days didn’t sit until the afternoon. I was lucky enough to have as co-researcher David Marsden, who was by then already on the road to becoming one of the world’s best neuroscientists specialising in dopamine. In 1968, when I became a minister, I stopped working as a doctor.