Having a professional rather than manual job was also related to a slight improvement in thinking and memory performance in older people. Those who had worked in professional jobs tended to recall an average of 12 details from a short story, compared with 11 for those who had worked in manual jobs.
"Finding these predictors is important because if we can understand what influences an individual's cognitive performance in later life, we can determine which aspects might be modifiable by education or lifestyle changes like exercise, diet or sleep, which may in turn slow the development of cognitive decline," said Dr Jonathan M Schott, the study author, of University College London and a member of the American Academy of Neurology.
"We found that childhood cognitive skills, education and socioeconomic status all independently influence cognitive performance at age 70."
The study involved 502 people born during the same week in 1946 and took cognitive tests when they were eight. Between the ages of 69 and 71, they took tests again. One involved looking at various arrangements of geometric shapes and identifying the missing piece from five options. Other tests evaluated skills such as memory, attention, orientation and language.
The findings suggest that the early years of development may be crucial for mental health in later life and questions the theory that cognitive decline could be delayed through lifestyle choices in later adulthood.
Some scientists have suggested that keeping the brain active in middle age, such as by doing crosswords, can help build up cognitive reserve and stave off dementia. But others now think the effect is caused by reverse-causality, with those who enjoy crosswords already having greater cognitive skills.
Dr Carol Routledge, director of research at Alzheimer's Research UK, said: "This study sheds more light on the complex relationship between memory and thinking skills in early life and our cognitive ability as we get older." The research was published in the journal Neurology.
