Should we be worried about older politicians?

Brain volume diminishes over time. In healthy people, the prefrontal cortex is the region of the brain with the most age-related volume loss, of roughly 5% per decade. Through its connections to other parts of the brain, it helps manage executive function: a complex set of mental processes that has been likened to a thermostat or the conductor of a symphony. It’s key to discussions of leadership capacities because it’s involved in areas like problem-solving, goal-setting and impulse control.

Executive function declines gradually during a person’s 30s, and this accelerates as we enter our 70s. White matter disease – a group of conditions caused by damage to the white matter in the brain – also contributes to executive dysfunction, and affects about a third of people aged 65 and older. Executive dysfunction can show up in reduced impulse control and increased repetition of thoughts and behaviours.

A significant proportion of people over 65 have some impairment of executive function, “I think as a general break point, 65 is reasonable,” says Mark Fisher, who directs the Center for Neuropolitics at the University of California, Irvine. Other structural changes in the brain become solidified around this age as well – mental processing speed has been shown to decline from around the age of 60 in a study using US data. 

The very loose threshold of 65 applies to the US, where the overall life expectancy at birth is 76. However, it may be different in countries with markedly different life expectancies and health systems (and there is also substantial racial and other inequality within the US that affects longevity). For example, the life expectancy for men in the US is 73. This is lower than in the top countries, but much higher than the life expectancy of 60 for men in Cameroon, whose president, 90-year-old Paul Biya, is said to be the world’s oldest national leader.