Boys are at greater risk for delayed language development than girls, according to a new study using data from the Norwegian Mother and Child Cohort Study. The researchers also found that reading and writing difficulties in the family gave an increased risk.
"We show for the first time that reading and writing difficulties in the family can be the main reason why a child has a speech delay that first begins between three to five years of age," says Eivind Ystr-m, senior researcher at the Norwegian Institute of Public Health.
Ystr-m was supervisor of Imac Maria Zambrana, a former PhD student at the Norwegian Institute of Public Health who conducted the research in this study as part of her doctoral research.
The researchers used data from questionnaires completed by the mothers who are participating in the Norwegian Mother and Child Cohort Study (MoBa). The study included more than 10,000 children from week 17 of pregnancy up to five years of age.
"MoBa is a large study with a normal cross-section of the population. It gives us a unique opportunity to examine changes over time, the scope and any risk factors for delayed language development," says Ystr-m.
Mostly boys
The researchers classified the language difficulties at three and five years of age in three groups: persistent delayed language development (present at both times), transient delayed language development (only present at three years) and delayed language development first identified at five years old.
Boys are in the majority for the groups with persistent and transient language difficulties. Ystr-m explains that boys are biologically at greater risk for developmental disorders in utero than girls. British scientists have measured the male sex hormone (testosterone) in amniotic fluid and they found that the levels were related to the development of both autism and language disorders. Ystr-m points out that boys are generally a little later in language development than girls, but that most catch up during the first year. Therefore, many boys could be at risk of persistent language impairment and increasingly have transient language difficulties that disappear before school age.
The researchers found that gender was irrelevant for the third group who have language difficulties that begin sometime between three and five years of age.
Hereditary factors
We have good knowledge about normal language development in children. Many genes are important for language development and research suggests that different genes are involved in different types of language difficulty.
"Reading and writing difficulties in the family are the predominant risk factors for late-onset language difficulties. We see no language problems when the child is between 18 months and three years old. They are latent" says Ystr-m.
The researchers believe that both specific genes and factors in the child's external environment can lead to delays in language development at three to five years of age.
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