Why a higher IQ means a longer life

Having a high IQ at a young age increases the likelihood of leading a long and healthy life. But it’s not just down to genetics. Our cognitive abilities are not static – starting school early, having a long education and physical activity are best for training the brain.

Illustration: Katrin Rodegast

Text: Maja Lundbäck, First published in Medicinsk Vetenskap nr 3 2021

They exercise more, are healthier, richer, fitter and have lower rates of mental illness – they also live longer than most. Those with high intelligence really have won the best prize in the lottery of life – or – is it a lottery?

Torkel Klingberg is a professor of neurology at the Karolinska Institute and is interested in how our various circumstances – our genes, socioeconomic circumstances and length of education – can affect how our cognitive abilities develop.

Intelligence predicts success

“Intelligence can predict success, such as how a person will do in school, and what kind of job, income and life satisfaction they’ll achieve,” he explains.

But it’s not the same thing as intelligence being statistical. We used to think of intelligence as innate and more or less stable. But now, more and more studies are showing that it’s not just a question of heritage – first and foremost, it’s clear that the time we spend at our school desks is very important.

“But do you choose a long education because you are intelligent or is it that education improves your intelligence? We need to figure out the causality – and research has made a lot of progress in this area,” says Torkel Klingberg.

Torkel Klingberg. Foto: Sara Mac Key

Several variants of intelligence

There are various definitions of intelligence, but for research purposes, we usually base intelligence on something that we can measure using cognitive tests, such as intelligence tests.

Researchers, regardless of whether they work within the field of neurology, pedagogy, public health or psychology, usually now differentiate between different types of intelligence: fluid or crystallised intelligence. We sometimes also talk about working memory and visualisation ability.

Crystallised intelligence is our collective knowledge and experience bank, and this can continue growing into our old age. Those with high crystallised intelligence have good general knowledge, good verbal understanding and often get full marks on quizzes. Fluid intelligence relates to the ability to think, reason and solve new and unfamiliar tasks quickly, regardless of our collective experience. Younger people up to 30 years old are usually best at this.

A definition of intelligence

On 13 December 1994, 52 intelligence researchers agreed on a definition of intelligence which was published in the Wall Street Journal:

“Intelligence is a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. It is not merely book learning, a narrow academic still, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings – “catching on”, “making sense” of things, or “figuring out” what to do.”

Correlated with health and lifespan

French psychologist Alfred Binet invented the first intelligence test just over 100 years ago when he developed tests in order to identify children with learning difficulties. In Sweden, the Wechsler scale is used to generate a person’s IQ (intelligence quota). The Wechsler scale tests a person’s numeric, spatial and verbal abilities. For examining children with neuropsychiatric diagnoses or intellectual disabilities, the WISC (Wechsler Intelligence Test for Children) is used. This test measures IQ based on the four cognitive abilities verbal function, perceptual function, working memory and speed.

It is primarily the G factor, general intelligence, that we are interested in determining. Intelligence tests are designed so that if a person performs well in one area, they also tend to do well in other areas.

We now know that there is a reverse correlation between high intelligence on the one hand and illness and death on the other. If you compare the 25% of people with the highest intelligence with the 25% with the lowest intelligence, the latter are at twice the risk of dying prematurely.

Anton Lager Photo: Anna Molander
Anton Lager Photo: Anna Molander

“But it’s not only those at the lower end of the scale that suffer from diseases. The higher your intelligence, the lower your risk of becoming ill and dying prematurely. This correlation applies across the entire intelligence scale,” says Anton Lager, researcher in public health at the Department of Global Public Health at the Karolinska Institute.

A few years ago, Anton Lager showed in a thesis that boys born in 1928, who were followed from the age of 10 up to 70, lived longer the higher their IQs. However, the same study showed that girls with high IQs did not live any longer than women of the same age with lower IQs, in fact it was the opposite. He did not know the reasons behind the difference between the genders in his study, but he guesses that it may be to do with smoking.

However, other studies have not found this gender disparity. He therefore still believes that each extra IQ point prolongs our time on Earth – for both men and women. People who qualify for Mensa, the society for people with high IQs, and who are therefore smarter than 98% of the population, on average live longer than those who do not qualify.

Intelligence can change

Anton Lagers interest in IQ centres around the relationship between health, class and intelligence – and his research was triggered by hearing about a study that shocked him. American psychologist Linda Gottfredson suggested that working class people died earlier than middle class people due to lower intelligence.

“I thought this was terrible, especially if you also believe that intelligence is innate and stable. But it still became the background for my thesis. What makes the connection between class, intelligence and health so interesting is that intelligence can be influenced,” he says.

So maybe it’s not only at birth when we have the chance to win the IQ lottery. That the brain can be moulded and developed based on what we do has fascinated Torkel Klingberg for a long time. He discusses how Norwegian researchers have proved that an extra two years in school increases a child’s IQ by around one point on average. When Norway introduced extended schooling, it was implemented one region at a time, which made it easy to compare how the IQs of students of the same age developed depending on how long they went to school for. The introduction of nine-year compulsory education in Sweden was shown to have the same affect in a later study by Anton Lager.

Illustration: Katrin Rogestad

Education increases IQ 

The effect on schooling on IQ has been proven in several ways, for example by comparing children born early compared with late in the year.

“By comparing the number of months spent in school since birth, you can see that schooling influences intelligence and working memory more than chronological age,” he explains.

Studies also show that people monitored for 20 years, from 12 years of age, gained a higher IQ the longer their education.

But what role do genes and environment play in successful schooling and the opportunities to develop your intelligence? In a recently published study of just over 300 children, Torkel Klingberg and his colleague Bruno Sauce looked at how genes influence the development of working memory, partly in line with children growing up, and partly depending on how much working memory training children receive.

“Working memory increased not only with age, but also with education. The same genes affected both education and development. This also points to the fact that children’s development is largely an effect of education,” says Torkel Klingberg.

However, one thing that still bothers Anton Lager is the fact that children that are above average from the start find it easier to benefit from teaching. He believes disadvantaged children would therefore need more education than they currently receive.

“Of course, school is supposed to even out differences, but if that were the main objective, children with the greatest difficulties would be given the longest education. As things stand at present, school increases disparities,” he says.

Fact: One child in every class is particularly gifted

One in every twenty children, just over one in each class, is considered to be particularly gifted. These students stand out in their capacity for nuanced reasoning, abstract thinking and understanding complex ideas. They usually learn quickly, have a good memory and learn from experiences beyond the obvious. Some children that are particularly gifted may underperform in school, either to fit in or because they’ve lost the desire to learn. According to the Swedish Education Act, since 2010, students who easily achieve knowledge objectives have had the right to receive guidance and stimulation to progress further in their knowledge development.

Source: Swedish National Agency for Education

Erika Jonsson Laukka Photo: Maria Wahlberg
Erika Jonsson Laukka Photo: Maria Wahlberg

Easier in young age

But we still don’t seem to know how long we have to improve our IQs. In any case, it’s now less proven that you can increase your IQ as a middle-aged or elderly person. It might then be about maintaining your abilities and skills. Erika Jonsson Laukka is a researcher in psychology at the Aging Research Center, Karolinska Institute and studies changes in cognitive abilities in connection with ageing.

“Intelligence is largely established during the first half of our lives, when we’re children, growing up and studying at university. If you performed well in an intelligence test when you were young, and the various cognitive domains that these measure, you will maintain your abilities as you get older,” she says.

Crystallised intelligence can stay intact up until your eighties, according to Erika Jonsson Laukka.

“The function that is most affected in line with ageing is mental speed. Many intelligence tests and cognitive tests are timed. Pure speed tests peak among those aged 25-30. The memory is usually maintained stably up until your 60s and after that a decrease can be seen,” she says.

However, the older we get, the greater the variation researchers see in how we perform in cognitive tests.

It could of course be early onset dementia which negatively affects cognitive abilities. But it is also common for cardiovascular disease to cause damage to the brain. If you have high blood sugar or blood pressure and don’t do anything about it, you run a higher risk of damage.

“Even small blood vessels in the brain can be affected. This might not lead to rupture or a heart attack, but it can still make the blood flow more slowly so that less damage arises, which affects the brain’s communication ability,” she says.

This could affect, for example, episodic memory, a complex cognitive ability which involves several regions of the brain. This manifests itself by not being able to remember things from your own life, which you did yesterday or last week.

Illustration: Katrin Rodegast

Brain health can always be improved

However, improving brain health is possible, and it’s good to start no later than in your 50s. Good health at this age from a cardiovascular perspective is very important as regards how you age cognitively. You should avoid diets that make you overweight. The Mediterranean diet contains a lot of fruit and vegetables, and healthy fats which the brain needs. A lifestyle factor that is also very important for how we cognitively age is exercise.

“Physical activity can help us to keep cardiovascular-related risk factors in check,” says Erika Jonsson Laukka.

Breaking a sedentary lifestyle is mainly what promotes brain health in those who are a little older.

“We’ve looked at older people and seen that the most important thing is to not end up in the worst category, which involves exercising less than four times a month,” she says.

Research has also shown that cognitive training can cause the brain’s grey matter to increase in volume and positively affect the neural pathways in the white matter, which promotes communication between different parts of the brain.

“It’s always good to activate the brain, learn new things, such as a new language, a new dance or how a computer works. It’s about challenging yourself and doing things you haven’t done before. Social interaction is also stimulating and good; it’s important for the brain to have company,” says Erika Jonsson Laukka.

But if it´s a long life you’re mainly after, there are also other things you can do to maximise your chances.

“It’s not like rich people are healthier because they’re smart. They’re healthier because they generally have higher incomes, better jobs and live in better areas. Anyone can try to acquire these advantages that are often associated with those with high intelligence and good socioeconomic backgrounds. You can stop smoking, monitor your blood pressure and try to surround yourself with people who are good for you,” says Anton Lager.

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