Children with a limited vocabulary at the age of five may be at increased risk of poor literacy as adults, according to a study.

UK researchers found that among more than 11,000 34-year-olds followed since childhood, those who had shown "very limited" language development at age five were at increased risk of low literacy.

As adults, one-third still showed a "poor grasp" of reading and writing skills, the researchers report in the journal Paediatrics.

Still, the researchers say, the flip side of that finding is that two-thirds of children with significant language problems went on to develop competent literacy. And certain characteristics of children's home life seemed to make a difference in whether early language problems persisted.

One of those was whether parents read to their children on a regular basis.

"There is ample evidence that reading to a child can help prevent early problems in child development and learning," said lead researcher Ingrid Schoon, of the University of London.

"Our study suggests that reading to a child might also have long-term beneficial effects," she said.

The findings are based on 11,349 UK adults who were part of a long-term national study of children born in 1970. At the age of five, participants took a standard vocabulary test where the child is shown a set of pictures, then asked to pick the one that is associated with a particular word. At the age of 34, they took a test of basic literacy.

Overall, four per cent of participants were found to have "very limited" language skills at the age of five. These children were nearly seven times more likely than their peers with normal language skills to later score poorly on the adulthood literacy test.

However, that risk was diminished when the researchers accounted for other factors that commonly went hand-in-hand with childhood language difficulties.

Children from families with no income from paid employment were at greater risk of poor adulthood literacy, as were those who lived in crowded homes. Time spent reading with parents also mattered; five-year-olds whose parents read to them daily had a lower risk of adulthood literacy problems.

The effects of those factors, Dr Schoon's team found, were independent of language problems in childhood, and suggest ways to help overcome such early difficulties with words.

"Without attempts in improving the socioeconomic and housing conditions, as well as the literacy environment experienced by the child during the early years," the researchers write, "the likelihood of success in improving language and literacy skills may be diminished".