Hello and welcome to more or less on the BBC World Service. We are weekly guide to the

numbers all around us and I'm Tim Halfard.

Later we'll ask whether pets are eating 20% of the world's meat. But first we're going

to look at the long-running American presidential election and we'll be tackling head-on

an issue that's often only hinted at dementia and all these septicenarians running for the

presidency.

President Trump was 70 when he was inaugurated. That's the oldest of any first time president.

He's not getting any younger and all three of the leading challengers would beat that record

if they were elected. Elizabeth Warren would be 71 years old on an

auguration day. Joe Biden would be 78. Bernie Sanders would be 79. Trump of course would be

74 if reelected. So without considering any particular candidate should American voters

be taking the risk of dementia seriously or is it something that looms larger in the

imagination than in the data? Demographer Dr Ezra Fisherman has studied the probability

of developing dementia at older ages. I asked him what the risk is that someone in their

70s might develop dementia over the next few years.

It's low but it's not trivial. My estimates depending on the precise ages could be something

in the area of 5 to 8% chance. It depends on the exact ages.

And that's over a single presidential term over the next four years.

Right. Yeah, 5 to 8%. So you say it depends on the ages. So give us some examples and

we can link them to particular candidates but obviously you are talking about population

averages here. You're not speculating on any individual.

That's correct if we take for instance a male would have, I estimate about 8.7% chance

...