An international team of scientists has discovered that genetic factors are likely to influence how much a personâ€™s intelligence changes, in comparison to their peers, throughout their lifetime. The study of nearly 2,000 people, which was part-funded by Alzheimerâ€™s Research UK, is the first of its kind to look at a large sample of people tested on two occasions more than half a century apart.
Scientists from the University of Edinburgh and the University of Aberdeen collaborated with researchers in Queensland, Australia to study unique cohorts of people, known as the Lothian and Aberdeen Birth Cohorts. The participants had all taken an IQ-type test at the age of 11, as part of the Scottish Mental Surveys of 1932 and 1947. Decades later, the researchers tracked down surviving members and asked them to re-take the same and other cognitive tests at age 65, 70 or 79. This allowed them to see how peopleâ€™s intelligence test scores had changed from childhood to old age. By collecting a wealth of extra information on the participants â€“ such as their medical history and social and environmental factors â€“ the scientists aim to uncover different things that influence mental ageing.
In the current study, the DNA of 1,940 people was analysed using a genetic chip that tested more than half a million genetic markers. The researchers set out to discover whether changes â€“ and stability â€“ in intelligence over a lifetime could be down to genetic factors.
Using a new, complex statistical method, the team was able to estimate how far genetic variations were likely to contribute to intelligence over a lifetime. Their results, which are published online in the journalÂ Nature, suggest that genetic factors contribute to intelligence in childhood and old age, and to about a quarter of the changes in between. The scientists explain that further study is needed to identify the exact genetic causes of changes in intelligence.
Dr Simon Ridley, Head of Research at Alzheimerâ€™s Research UK, said:
â€œCognitive decline in old age is a known risk factor for Alzheimerâ€™s disease, and understanding what may cause or protect against this decline is crucial for dementia research. This study has identified a possible genetic cause for changes in cognitive ability over time, and it will now be important to discover exactly how our genes may contribute to cognitive decline. If we can understand how our genes influence cognitive decline, this may provide new clues for developing effective treatments for Alzheimerâ€™s.
â€œWeâ€™re delighted that funding from Alzheimerâ€™s Research UK has helped make this study possible, and itâ€™s now essential that these results are followed up. With 820,000 people affected by dementia in the UK, we urgently need to find new ways to treat and prevent the condition, and that means we must invest in research.â€
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