By Tahiat Mahboob  

It was June 4, 1947. As part of the Scottish Mental Survey 1947, 70,805 school children born in 1936 took the same standardized cognitive intelligence test. The test results of these 11-year-olds were recorded in ledgers and archived.

Forgotten for nearly five decades, they resurfaced when Professor Ian Deary of the University of Edinburgh and Professor Lawrence Whalley of the University of Aberdeen learned about them. The ledgers are helping scientists understand how and why people’s thinking skills change with age.

How To Keep Your Brain Young

"We have baseline cognitive function from when people were healthy in early youth," Deary said in an interview with the BBC. "It means we can estimate each individual's change in cognitive function across the life-course from childhood to old age, and then study them within old age."

Scotland is the only country in the world to have ever tested the intelligence of an entire age group. Organised by the Scottish Council for Research in Education, the 1947 survey used a validated intelligence test known as the Moray House Test No. 12. The test contained a variety of problem sets: following directions, same–opposites, word classification, analogies, practical items, reasoning, proverbs, arithmetic, spatial items, mixed sentences, cypher decoding, and other items. It had previously been administered in 1932 to 87,498 children born in 1921.

Those who took the test were nearing the age of 70 in the early 2000s — an important age for studying thinking skills in later life. Deary and his team reached out to these test-takers living in Edinburgh and the surrounding Lothian area and invited them to participate in an aging research project, known as The Disconnected Mind. One thousand and ninety-one former test-takers agreed to take part. They came to be known as the Lothian Birth Cohort 1936 (LBC1936).

Since the project began in 2004, the LCB1936 has been tested four times, every three years, at ages 70, 73, 76 and 79. Each time the participants repeat the same test they took in 1947 along with 15 other ones that test their thinking skills. Also, they undergo an MRI brain scan, provide blood for genetic and biological testing, take medical and physical tests and provide information on their activities, diet, home life, mood, personality, well-being and more.

The information is recorded in a database and analyzed in numerous ways to learn how people’s brains and thinking skills change with age and what factors are involved.

Here are two key findings:

How important is white matter?

The human brain consists of gray matter and white matter. The gray matter contains the nerve cells. The white matter is composed of nerve fibers and myelin. These nerve fibres form the connections between the nerve cells. The project found that the health of white matter and thinking skills are connected. The healthier the white matter, the sharper people tend to be in later life. Based on the LBC1936 research, a paper in the Journal of Neuroscience led by Dr. Stuart J. Ritchie at the University of Edinburgh shows that declines in white matter in the LBC1936 over three years (measured in the same way on the same scanner) is significantly related to three-year declines in general thinking skills (on the same tests, over the same period).

How much do genes actually control?

The Disconnected Mind project team studies how genetic and environmental influences contribute to change in cognitive function as people age. They have discovered that approximately 24 per cent of that change (between ages 11 and 70) is due to genetic influences. Three-quarters of the change in cognitive function are influenced by other factors including lifestyle choices. That means people do have some control over how their cognitive functions evolve as they grow older. It’s not all because of genes.

Ian DearyDr. Ian Deary holding a 3D model of a human brain

According to Deary, cognitive aging research isn’t the only thing the LBC1936 data is helping. Collaborators from Edinburgh, the United Kingdom and around the world are using the data in other studies, such as conditions relating to blood clotting, the immune system and eye health.

As for his area of study, Deary knows just the way in which the research will have an impact.

“Understanding brain aging will give us a rational basis for the future design of new ways to prevent and treat age-related cognitive impairment,” Deary said in an interview with Age UK, a charity that provided funding for The Disconnected Mind.

Watch How To Keep Your Brain Young.