Children born to older mothers are more likely to do better in intelligence tests than those born to younger women, new research has found.

Children born in 1970 to mothers aged 25 to 29 were more likely to perform better in tests of cognitive ability than those born to mothers who were 10-years older.

The same was true of children born in 1958, so modern results appear to have reversed the result.

The "dramatic" new results come from children born in 2001 and researchers have suggested that they are influenced by the increased resources and attention that first-born children receive from their parents.

Women in the older bracket were likely to be bearing their "third or fourth child", not their first, the study found.

Older mothers in recent years also tend to be more advantaged than similar women in the past, with better education and jobs and a lower probability of being smokers during pregnancy.

The study was carried out by the London School of Economics (LSE) and the Max Planck Institute for Demographic Research.

"Our research is the first to look at how the cognitive abilities of children born to older mothers have changed over time and what might be responsible for this shift," said the paper's lead author, Dr Alice Goisis. "It’s essential to better understand how these children are doing given that, since the 1980s, there has been a significant increase in the average age of women having their first child in industrialised countries."

She added: "Cognitive ability is important in and of itself but also because it is a strong predictor of how children fare in later life—in terms of their educational attainment, their occupation and their health."

Researchers studied data from three long-term studies in the UK, the 1958 National Child Development Study, the 1970 British Cohort Study and the 2001 Millennium Cohort Study. Children’s cognitive ability was tested when they were 10 or 11.

They said: "When the researchers took the mothers’ social and economic characteristics into account, the differences across cohorts disappeared.