Discussion
This systematic review and meta-analysis summarized the currently available research related on the prevalence of DCD in preterm children, exploring subgroups by gestational age, assessment tools, and different cut-off scores on standardized assessments. Our results demonstrated that the overall prevalence of DCD among preterm children was 21% based on the 32 studies involving 31184 preterm participants. The analysis also showed that preterm children are two times more likely to have DCD than their full-term peers. The prevalence and risk of DCD vary according to gestational age and different assessments tools and cut-off criteria.
Up to our knowledge, this is the first systematic review and meta-analysis exploring DCD in different gestational age groups. The estimate rates were higher as gestational age decreased, aligned with previous studies.9,48.The pooled prevalence of DCD in extremely, very, and moderate/late preterm children was 26%, 23%, and 12%, respectively. It is well known that extremely preterm children are at higher risk for several adverse outcomes, impacting their global neurodevelopment compared to other preterm groups.2Our results corroborate previous studies analyzing DCD or other motor impairments, showing a higher rate of delays in extremely preterm children.2 However, these results could be more accurate if all studies in this review had reported prevalence according to gestational age. The studies that described only very preterm participants, moderate/late preterm, or even preterm below 37 weeks of gestational age, usually consider all preterm children below the specific cut-off point. That means that in a very preterm cohort, extremely preterm children may be included, as well in a moderate/late preterm cohort. We hypothesized that if all these data were broken down by gestational age, the differences between rates in extremely, very, and moderate/late preterm children would be higher.
We found similar results from previous systematic reviews when considering prevalence according to assessment tools and cut-off point criteria for DCD. The pooled estimate rate for DCD in studies using the 5th percentile on MABC was 18.7% and 31.1% with the 15th percentile. Whereas Williams and colleagues (2010)10 reported an overall pooled estimate of 19% of DCD in preterm children when the studies used the 5th percentile, and 40% with the 15th percentile in the same assessment tool. There is a divergence in the literature about the percentile cut-off to be used; 12 studies used the 5th percentile while 10 studies used the 15th percentile. The MABC seems to be the most used standard tool to detect DCD in children from 3 to 16 years old. However, in its manual, the categorization is described as: ≤ 5th percentile = significant motor difficulty; 6-15th percentile = careful monitoring suggested; and > 15th percentile = no significant motor difficulty.49 Thus, the DCD condition criteria are unclear, giving scope to different interpretations. While some studies prefer to consider the most restricted criteria for DCD (5thpercentile),6,21,23,24,26,27,29,35,39,42,44,46 others report the children “at risk for DCD” (6-15thpercentile) in the same group for analysis.19,20,28,30-32,36,40,41,45 That said, there is a large range between the results and the need to establish standard cut-off criteria to compare the results of different studies, populations, and regions.
Further, the second most used tool presented in this systematic review was the DCDQ. The pooled estimate rate from studies using this instrument was 20% of DCD in preterm children. The DCDQ is a brief parent questionnaire designed to screen for coordination disorders in children aged 5- to 15-year-old, while LDCDQ assesses children from 3 to 4 years old.50 As with all other self-reported questionnaires, its subject to biases as interpretations of the questions, honesty, memory, and others. In contrast, this could be the best tool to assess a large sample as a population-based cohort, which is the case in 4 of the 6 studies found in this review with this assessment tool.9,35,38,48
We also found 18 studies comparing DCD in a preterm and full-term group, the present analysis showed that preterm children are two times more likely to have DCD than their full-term peers. This result is different from two previous systematic reviews on this topic. The first one reported that premature children are at risk three to four times higher,10 and the second one reported six to eight times higher11 than the general population. This may be justified because one of these reviews, although had addressed the DCD throughout the article, included studies with “motor impairments, excluding cerebral palsy”,10 which may embrace other neurodevelopmental problems besides DCD. The other systematic review included studies only with very preterm or very low birth weight children, which does not consider the moderate/late preterm group that presented the lowest prevalence rate in our review.
Therefore, we advanced the previous systematic reviews10,11 by comparing DCD prevalence across different classifications of prematurity and full-term children. It was observed that the risk of having DCD increases as gestational age decreases. Extremely preterm are at over 3 times higher risk than full-term children, while very preterm children are at over 2 times higher, and moderate/late preterm at 1.5 times higher risk. Two previous studies34,42 that assessed full-term groups and different preterm groups according to gestational age have also found similar results.
Regarding cut-off criteria and assessment tools, comparing between preterm and full-term children demonstrates a similar quantity of studies using each criterion. There were also different results for each analysis. Preterm children are at over 3 times higher risk of DCD than full-term peers when using the MABC 5th percentile cut-off, and over 2 times when using the 15th percentile. Analyzing studies that used DCDQ, preterm children were 1.5 times at higher risk for DCD. It was observed that the stricter the criteria, the higher the risk, which may represent the sensibility and specificity of the instrument.
Interestingly, no studies were found with preterm adolescents or adults. This systematic review did not limit participants’ age, but all studies ranged from 3 to 13 years old. Only one of the studies assessed the same children at three time points, 5, 7, and 13 years. The authors showed a decreased rate of DCD in very preterm children from 47.9% at 5 years of age, to 28.5% at 7 years and 27.8% at 13 years of age.45 Considering that, future systematic reviews should analyze the DCD rates by age at assessment, and future original studies should focus on the older preterm population to comprehend the impact of prematurity late in life.
Furthermore, only two studies in this systematic review were from LMIC.9,37 The lack of studies on LMIC may portray the difficulties that researchers face with the high-cost national studies. The follow-up care of preterm children is expensive as appropriate standardized assessment tools, making it difficult for researchers and professionals in these countries to assess these children longitudinally for research or clinical practice. Besides, the lack of diversity in published research, especially from non-WEIRD countries, has been reported in the literature on children’s development - around 10 % of study participants in research are from Asia, Africa, South / Central America, or the Middle East;51 although in these regions lived the majority of the world population.
This review highlights the magnitude of DCD risks in preterm children. DCD is considered a subtle motor difficulty and may be undetected by parents and clinicians, requiring standardized assessments. Since this condition is not identified before 3 years old, attempting to detect early soft signs and longitudinal follow-up with children at risk is essential. Even before the DCD diagnoses, these children could benefit from early intervention as soon as a motor delay could be identified in the first years of life to take advance children’s neuroplasticity. Further, the results demonstrated a higher risk for DCD in extremely preterm children; therefore, this population should have even more attentive care for motor difficulties in the first years of life until preschool and school age.
A limitation of this systematic review is the high heterogeneity between included studies. Some reasons may help in explaining this heterogeneity. First, the population was different in each study; we tried to minimize these differences by analyzing gestational age groups. Even so, some studies analyzed only one combined preterm group (born before 37 gestation weeks), and others categorized the groups by gestational age. Therefore, the isolation of this variable was challenging. Second, the assessment tools and cut-off points used were different, portraying different results. We also control the different cut-offs as much as possible. However, even then, some studies were excluded from the analyses lacking other studies with the same tool.
Moreover, third, the age at assessment may have some impact on prevalence outcomes. This variable was not analyzed in the present review for the high complexity of separating also the age groups, as we had separated the gestational age in the analysis. We suggest future research and reviews trying to control the age at assessment.