The 90-year-olds at the cutting edge of brain-ageing research
BBCWhen Hamish McKenzie took a test in 1947 as part of a study into how Scots performed intellectually, he did not expected to still be having his brain power measured 80 years later.
Hamish, who was a pupil at George Watson's College in Edinburgh, was one of more than 70,000 11-year-olds who sat the test as part of the Scottish Mental Survey.
Eight decades later - as Hamish and his peers reach 90 - there are 150 taking part in the latest stage of a project looking at how the brain ages.
They were originally part of the 1936 Lothian Birth Cohort study, run by the University of Edinburgh.
Hamish still remembers taking the first test with the other boys at school.
It involved tasks such as finding the final element after being given a four-item pattern.
"We were quite competitive," he says.
"We didn't want to get left behind.
"I did want to do well."
The results of the 1947 test were significant at the time but were stored away and almost forgotten, until academics at the University of Edinburgh realised how valuable they could be if they could trace the participants to see how their brains had fared over the years.
So the study was resurrected in 2004.
Original participants from the Lothian area were traced as they approached 70 and continue to be monitored as they all turn 90.
Their answers over the decades have yielded some of the best information available on how the brain ages, according to the director of the study, Prof Simon Cox.
He says being able to track their brains from 11 to 90 is extremely unusual and incredibly valuable.
"One of the most interesting findings related to the mapping between the early life functioning test and the same test at age 70," Prof Cox says.
"Cognitive scores were relatively stable and so what that means is that people who were doing pretty well at age 11 were still those doing pretty well in older age.
"A lot of the signals that we were getting when we measure cognitive functioning in older adulthood is actually attributable to differences that were pre-existing and present at childhood and that motivates the question, what else?"
Iain Bruce, who has just celebrated his 90th birthday, says he is pleased he's been part of an important study.
"I think what can be achieved is for the next generations and generations to come, because the mind to me has not been investigated enough," he says.
"If we can avoid people getting dementia and Alzheimer's because of information that's been accumulated through this cohort, that 's wonderful.
"It won't do me any good, but I can look back down and say it was partly due to me that these people are now having a better life."
The study has sparked hundreds of international academic papers.
Prof Cox says it hasn't come up with any single solution for ageing but rather points towards a range of factors, such as lifestyle, genes and activity.
"Each individual effect that we look at or each individual candidate predictor of cognitive ageing on its own really doesn't explain a huge amount of the differences that we see," he says.
"But if you add them all up together there's an incremental additive effect whereby lots and lots of small effects would add up to explain quite a lot of the differences in cognitive ageing.
"So, it's more marginal gains and less magic bullet."
And today's teenagers are also benefitting from 1936 Lothian Cohort study.
Pupils from Boroughmuir High School have used the research to design their own projects on keeping brains healthy and they've been passing on tips to younger pupils.
S6 pupil D'arcy said: "We made a powerpoint and activities to take out to a P1 class, just teaching them general simple facts about the brain.
"We also spoke to them about how they could keep their brain healthy by eating healthy and physical exercise.
"We also talk about neurons and what happens in the brain, and we look at scans from the births cohorts, looking at healthy and not so healthy brains."
Ninety-year-old Mary Groat is an advocate for finding ways to keep your brain healthy.
She did the test in 1947 and decades later she's still doing them, and she has a few tips on how to live well into your nineties.
"I do code words which is just like a crossword," she says.
"I don't watch a lot of television. I go out to the community centre for a little game of bingo and then my family comes around so they keep me busy. "
Fellow participant Margaret Dryden says she has thoroughly enjoyed being part of the research.
"You were welcomed, you felt as though you counted," she says.
"It mattered and that's not always the case, especially when you get to 90.
"But it was a delight to have these conversations and learn more about yourself and other people."
After decades of giving their time to research, the participants have embarked on another wave of tests.
Prof Cox says they are leaving behind a rich seam of information.
"This study has led to many more studies, discoveries and contributions to broader scientific questions about ageing and beyond, which we could never have imagined at the beginning," he says.
"When you ask the participants 'Why do you take part?' they say 'This is for future generations'."
Prof Cox adds: "It's my job to ensure we realise the potential of the data. "
