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.