One in four kindergarten age children have sub-optimal developmental health.

That's the latest research finding from the long-term Growing up in New Zealand study.

The four-and-a-half-year-olds at a social and economic disadvantage, Maori and Pasifika children are more likely to be in that category.

Lead author Dr Jin Russell told Heather Du Plessis-Allan there needs to be investment in children's early years.

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