This review assessed the effects of early intervention on motor development in infants at high risk for, or with, developmental motor disorders. The authors concluded that pre-term infants benefit most from interventions simulating the intra-uterine environment, and term age infants benefit most from developmental programmes. The exclusion of studies based on publication limits the reliability of the authors' conclusions.

To review the effects of early interventions on motor development in infants at high risk for, or with, developmental motor disorders.

MEDLINE, CINAHL, AMED, PsycINFO and PEDro were searched from inception to July 2004; the keywords were reported. The reference lists of relevant reviews and primary studies were also checked. It was not reported whether any language restrictions were applied. Only articles that were published in journals with impact factors of at least 0.3 were considered eligible for inclusion.

Study designs of evaluations included in the review

No specific inclusion criteria relating to study design were described. The study designs included: randomised controlled trials (RCTs) (level one evidence); non-randomised controlled trials, or prospective cohort studies with a control group (level two evidence); case studies with control participants, or cohort studies with a historical control group (level three evidence).

Specific interventions included in the review

Studies that included an intervention that aimed to improve motor development, where the onset of the intervention in at least 50% of the participants was between birth and the (corrected) age of 18 months, were eligible for inclusion. The specific interventions identified in the review included methods to reduce stress, sensory stimulation, motor interventions, or strategies to enhance parent-infant interaction.

Participants included in the review

Studies that included infants with high biological risk for, or with, developmental disabilities were eligible for inclusion. The majority of studies included infants at high risk of developmental disabilities; other study groups included infants with cerebral palsy, Down syndrome, central nervous system injury, or delayed cognitive or motor development.

Outcomes assessed in the review

No specific inclusion criteria relating to outcomes reported were described. The studies included in the review reported a wide range of outcomes, such as various neuromotor and developmental tests.

How were decisions on the relevance of primary studies made?

The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.

The internal and external validity were the determinants for the methodological quality of each of the studies. The studies were rated as high, fair or low for both internal and external validity. Decisions about the internal validity were based on participant assignment, contamination, cointervention and blind assessment; decisions about the external validity were based on information about generalisability. Two reviewers independently assessed the internal and external validity of each study. Any disagreements were discussed until a consensus was reached. Agreement between the two reviewers was assessed using Cohen's kappa statistic.

The authors did not state how the data were extracted for the review, or how many reviewers performed the data extraction. Data were extracted on the specifics of the intervention programmes, the location of the intervention, and parental involvement. The interventions were also categorised according to whether they contained specific elements: procedures to reduce stress; sensory stimulation; motor intervention strategies; parent-infant interaction strategies.

How were the studies combined?

The studies were grouped according to the age of the infant at evaluation: interventions applied at the neonatal intensive care unit (NICU); interventions applied between discharge from the NICU and a corrected age of 9 months; interventions started between the corrected ages of 9 and 18 months. The studies were then combined in a narrative.

How were differences between studies investigated?

The results were discussed with reference to methodological quality, focus of the interventions, statistical significance of the results and measures of outcome assessment.

Thirty-four studies were deemed eligible for inclusion in the review: 23 RCTs (n=2,552), 4 level two studies (n=501) and 7 level three studies (n=202).

Agreement between reviewers for the validity assessment was rated as high using Cohen's kappa (0.86 for judgements of internal validity and 0.95 for external validity).

Internal validity was rated as high in 11 studies, fair in 15 and low in 8. External validity was rated as high in 5 studies, fair in 16 and low in 12.

Interventions applied at the NICU (17 studies).

Two fair- to high-quality RCTs demonstrated a significant positive effect of the intervention on motor outcome. The interventions in these studies focused on stress reduction combined with general sensory stimulation and general infant development using general sensory stimulation, stimulation of motor development, passive handling techniques and enhancement of parent-infant interaction. Five of the 9 studies that were rated as lower methodological quality suggested a positive effect of the intervention. The interventions in these studies included procedures to reduce stress, multimodal sensory stimulation, passive motor intervention strategies, or the facilitation of parent-infant interaction.

Interventions applied between discharge from the NICU and a corrected age of 9 months (8 studies).

Four fair- to high-quality studies evaluated the effects of neurodevelopmental treatment (NDT); however, none found statistically significant effects. Two high-quality studies assessed programmes that stimulated infant motor development; both studies reported statistically significant effects.

Interventions started between the corrected ages of 9 and 18 months (6 studies).

One high-quality study demonstrated a positive effect of specific motor training on motor development of infants with Down syndrome, while another high-quality study found that a general infant stimulation programme facilitated motor development more than NDT. The other high-quality study showed no significant effect. One of the 3 lower quality studies found a beneficial effect of general programmes on stimulating motor development.

Interventions applied between discharge from the NICU and a corrected age of 18 months (3 RCTs).

All 3 studies were rated as moderate to high validity. One study that evaluated NDT for half a year reported a positive effect on motor development.

The type of intervention that might be beneficial for infants at pre-term age differs from the type that is effective in infants who have reached at least term age. Pre-term infants seem to benefit most from interventions aimed at simulating the intra-uterine environment, whereas for infants after term age, intervention by means of specific or general developmental programmes has positive effects on motor development.

The review question was clear in terms of the participants and interventions. A wide range of interventions, study designs and outcomes assessed in the primary studies were included in the review. Several electronic databases were searched, but it was unclear whether any language restrictions were employed. Studies were excluded on the basis of publication, which means that there is a distinct possibility that publication bias is present. The methods used to select studies and extract the data were not reported, so it is not known whether any efforts were made to reduce reviewer bias and error. Aspects of the internal and external validity of the included primary studies was assessed and taken into account in the discussion of the results. Given the diversity of the outcomes, study designs and the interventions evaluated, a narrative synthesis was appropriate. The exclusion of unpublished studies and studies published in journals with a low impact factor, and the lack of reporting of review methods, limit the reliability of the authors' conclusions.

Practice: The authors stated that interventions in children at risk of developmental disabilities should be adapted to the infant's age (interventions beneficial for infants at pre-term age differ from those beneficial for those who have reached at least term age).

Research: The authors stated that further studies assessing training and developmental programmes are needed to answer the question of whether the age at which the intervention starts is significant.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.