Lothian birth-cohort studies facts for kids

The Lothian Birth Cohort studies are two important research projects. They look at how people's intelligence and health change as they get older. These studies especially focus on how smart someone was as a child affects their mind and body in old age.

The studies follow people from the Lothian area of Scotland. These people took part in special tests called the Scottish Mental Surveys in 1932 and 1947 when they were children. By checking on them again when they are much older, researchers can see how their early intelligence connects to their thinking skills, mental well-being, and physical health later in life.

A lot of what these studies have found is about how stable intelligence is from childhood to old age. They also look at how genes affect our thinking skills and how our brains change over time. These studies are also leaders in a field called cognitive epidemiology. This field explores how intelligence is linked to different health outcomes. Professor Ian Deary leads the Lothian Birth Cohort studies. He works at the University of Edinburgh.

Understanding the Studies: A Look Back

The Lothian Birth Cohort (LBC) studies are follow-ups to older surveys. The LBC 1921 study checks on people who took part in the Scottish Mental Survey of 1932 (SMS1932). The LBC 1936 study follows those from the Scottish Mental Survey of 1947 (SMS1947).

These Scottish Mental Surveys were unique. No other country has ever tried to measure the intelligence of almost every child born in a specific year. Because the LBC studies could find these people again in old age, they could learn a lot. They could study how thinking skills change over a lifetime and how intelligence affects health. This was possible because they had a record of the participants' intelligence from when they were children.

Both Scottish Mental Surveys used a test called the Moray House Test No. 12. A person named Godfrey Thomson created this test. It's a good intelligence test with 75 different types of questions. These questions include following directions, classifying words, solving analogies, and doing math problems.

The Scottish Mental Surveys of 1932 and 1947

The SMS1932 was paid for by the Carnegie Corporation. It was part of a bigger project to study exams around the world. Its main goals were to find out how many children in Scotland had "mental deficiencies." It also wanted to gather information on how intelligence was spread across all Scottish students. This survey happened on June 1, 1932. It tested nearly all 87,498 children born in Scotland in 1921.

The SMS1947 was created to test a theory. This theory suggested that average intelligence in the United Kingdom was getting lower. This was thought to be because families with more children often had children with lower intelligence. This survey took place on June 4, 1947. It tested 70,805 children. This was almost all of Scotland's population born in 1936.

Finding the Old Data Again

The data from these Scottish Mental Surveys was lost for a while. Then, in the late 1990s, Professor Ian Deary and Lawrence Whalley found it again. The data was stored in a building at the University of Edinburgh. This building was called Charteris Land.

After the data was found, other follow-up studies began. These were called the Aberdeen Birth Cohorts of 1921 and 1936. They started recruiting participants in 1997 and 1999.

How the Studies Work and What They Aim For

A main goal of the LBC studies is to understand why people's thinking skills change differently as they age. The studies are also used for many other types of research. This includes looking at social, medical, and genetic factors.

Each time data is collected, researchers usually gather several types of information. This includes results from thinking tests and details about people's lives. They also record health habits, current health, fitness levels, and body measurements. They also take samples to check for certain substances in the body called biomarkers.

Many different groups have provided money for these studies. These include the Biotechnology and Biological Sciences Research Council, the Medical Research Council, and Age UK.

Lothian Birth Cohort 1921 (LBC1921)

Recruiting participants for the LBC1921 study started in 1999. Researchers mainly found people by tracing those who took the SMS1932 in the Edinburgh area. They used a health index to do this. Then, doctors contacted these potential participants to ask them to join the study.

The first main goal of the LBC1921 study was to find genetic markers. These markers could show who might have healthy thinking skills as they age. This included looking at how a specific gene, APOE, affects thinking skills. Later, the research focused on other genetic changes. These changes were linked to how the body handles stress. The third and fourth times data was collected, the main goal was to test a theory. This theory suggests that declines in physical and thinking abilities in old age share a common cause.

Lothian Birth Cohort 1936 (LBC1936)

Participant recruitment for the LBC1936 study began in 2004. Researchers found potential participants using the same health index. Then, the Lothian Health Board sent them a letter about the study.

The LBC1936 study started with a broader goal. It wanted to explore many different things that affect thinking skills in old age. This included looking at how money, health, feelings, and social life play a role. For the second wave of data collection, a special focus was placed on brain health. Researchers wanted to find out how the brain's white matter gets damaged. They also looked at how this damage relates to thinking skills declining with age.

Key Discoveries from the Studies

The LBC data has been used for many different research projects. For example, LBC1921 participants helped in a study. This study checked a test used to measure thinking skills in people with dementia. LBC1921 data also showed that having a more symmetrical face might be linked to better thinking skills in old age. Data from both studies has helped researchers understand changes in social class over time. It also showed that people's personality traits stay very stable in old age.

How Stable is Intelligence Over Time?

Path diagram showing how Moray House Test scores are linked at different ages in the LBC1921.

Studies using the LBC1921 data have given us the longest look at how stable intelligence is. They found that intelligence in childhood is strongly linked to intelligence in old age. This link exists because intelligence is a very stable trait. It's not because childhood intelligence protects against a decline in thinking skills later on.

The LBC1921 participants took the Moray House Test at ages 11, 79, 87, and 90. Their scores at all these ages were strongly connected. For example, the scores at age 11 were closely related to scores at ages 79, 87, and 90. This shows that intelligence stays very stable throughout a person's life.

Even though intelligence at age 11 is linked to intelligence in old age, it doesn't seem to affect how much intelligence changes between ages 79 and 87. This means that childhood intelligence is important because intelligence itself is stable. It doesn't mean that being smart as a kid stops your brain from changing as you get very old.

The LBC1936 participants also retook the Moray House Test in old age. In this larger group, there was a strong link between their scores at age 11 and age 70.

The Role of Genes in Thinking Skills

A picture of Apolipoprotein E.

One of the clearest findings from the LBC studies is about a gene called APOE. A specific version of this gene, called the E4 allele, is known to increase the risk of Alzheimer's disease. The studies found that this E4 allele is also linked to worse thinking skills and changes in those skills, even in people without Alzheimer's.

In an early LBC1921 study, having the E4 allele didn't affect test scores at age 11. But at age 80, those with the E4 allele scored lower. This suggests the allele increases the risk of thinking skills declining. Later research found that having the E4 allele was linked to a greater decline in abstract thinking and memory. In the LBC1936, the E4 allele was also linked to lower overall thinking ability at age 70.

Large-scale genetic studies, called Genome-wide association (GWA) studies, have confirmed these findings. These studies look at many genes at once. A GWA study that included both LBC studies found that the APOE E4 allele was linked to harmful changes in thinking skills. Another big study in 2015, combining data from many groups including the LBC studies, also found that the APOE gene was linked to overall thinking ability.

Data from both LBC studies also helped show that intelligence is influenced by many genes, not just one. The studies also helped estimate how much of the stable part of intelligence throughout life is due to genes. They found that most of it is due to genes, not the environment.

The Lothian Birth Cohort data has also been used in GWA studies for other health issues. These include cancer, stroke, and lung function.

Understanding White Matter in the Brain

A detailed image showing the white matter structure of the human brain.

Brain scans from LBC1936 participants have shown something important. The health of the brain's white matter is linked to how well people think as they age. White matter is like the wiring that connects different parts of the brain. One study found that the health of white matter explained 10% of the differences in general intelligence. This effect seemed to happen because of how fast people could process information.

The health of white matter also seems to be linked to changes in thinking skills. For example, healthy white matter in a specific part of the brain called the splenium is a sign of healthy brain aging. Also, having less damage in the white matter is linked to better overall thinking ability and faster processing speed at age 73. This was true even after considering their intelligence at age 11.

Additionally, white matter in some brain areas has been found to be weaker in people with the APOE E4 allele. This weaker white matter might explain some of the harmful effects of the E4 allele on thinking skills as people age.

Health, Habits, and Brain Aging

In the LBC1921 study, smoking was linked to a greater decline in thinking skills at age 80. The average IQ of people who currently smoked was lower than those who used to smoke or had never smoked.

Being physically fit was also linked to healthy brain aging in the LBC1921. This was measured by things like lung function, grip strength, and how fast someone could walk. In the LBC1936, being physically active was also linked to better overall thinking ability and faster processing speed at age 70. This was true even after considering their intelligence at age 11.

One great thing about the LBC studies is they can test for "reverse causation." This means they can see if an association between intelligence and something else is actually caused by earlier intelligence. For example, if a link between intelligence and caffeine use disappears after considering childhood intelligence, it suggests that being smart earlier might have influenced caffeine habits later. Reverse causation has been found for links between intelligence and caffeine use, body weight, alcohol use, and inflammation in the LBC1936 study.