The effectiveness of salt iodisation in improving the mental development of young children has not been assessed. We implemented a community-based cluster-randomised effectiveness trial in sixty randomly selected districts in the Amhara region of Ethiopia. We randomly allocated each district to treatment and randomly selected one of its villages. In parallel to national salt iodisation efforts, iodised salt was brought early into the markets of the thirty intervention villages before it became widely available in the thirty control villages 4–6 months later. The primary outcome was children’s mental development scores on the Bayley Scales. This was an intention-to-treat analysis using mixed linear models adjusted for covariates and clusters. The trial was registered at ClinicalTrials.gov, NCT013496. We assessed 1835 infants aged 5–11 months at baseline. The same children (85 % of the sample) were re-assessed at 20–29 months when all villages had iodised salt. At endline, urinary iodine concentration was higher in children in the intervention group compared with those in the control group (median 228·0 v. 155·1 µg/l, P=0·001). The intervention group had higher scores compared with the control group on the Bayley composite score (raw scores:130·60 v. 128·51; standardised scores: 27·8 v. 26·9; d=0·13; 95 % CI 0·02, 0·23) and three of the four subscales: cognitive (53·27 v. 52·54, d=0·13; 95 % CI 0·03, 0·23), receptive language (20·71 v. 20·18, d=0·13; 95 % CI 0·03, 0·24) and fine motor (35·45 v. 34·94, d=0·15; 95 % CI 0·04, 0·25). The introduction of iodised salt contributes to children’s higher urinary iodine concentration and mental development.

The motor and language skills, emotional and behavioural problems of 245 children were measured at school entry. Fine motor scores were significantly predicted by hyperactivity, phonetic awareness, prosocial behaviour, and the presence of medical problems. Gross motor scores were significantly predicted by the presence of medical problems. The fine motor scores of Māori children were poorer than those of Pākekā or children of other ethnicities, and right-handed children had better fine motor scores than left-handed children. There was some evidence that left-handed boys performed particularly poorly on tasks requiring fine motor skills. Children with medical problems had poorer gross motor scores than children without medical problems. Implications for the identification of problems at school entry are discussed.

This study investigated subgroup and task specificity of self-paced timing in children with developmental coordination disorder (DCD). Self-paced tempo (intertap interval) and timing stability (coefficient of variation) were measured in three repetitive tasks—hand tapping, foot tapping, and jumping in place—in 37 children aged 6 to 9 years classified into gross motor impaired (GM), fine and gross motor impaired (F&G), or coordinated control (CC) groups. Results showed that, although tempo did not vary between coordination groups, timing stability for the hand was significantly worse for the F&G motor impaired group (p < .05). Discriminant function analysis correctly classified 75% of CC, 67% of F&G, and 67% of GM children. Although timing inconsistency of hand tapping identified a coordination subgroup, these tasks provide only moderate prediction of group membership.