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Physical Activity Levels of Children With Down Syndrome

Fox, Bianca, MS, SPT; Moffett, Gwendolyn E., MAT, SPT; Kinnison, Clara, SPT; Brooks, Grace, SPT; Case, Laura E., PT, DPT, MS, PCS

doi: 10.1097/PEP.0000000000000556
SYSTEMATIC REVIEWS

Purpose: This systematic review of literature analyzed accelerometer use to measure physical activity (PA) in individuals 21 years and younger with Down syndrome (DS).

Summary of Key Points: Comprehensive search strategy conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Eight articles met inclusion criteria. Six studies reported children with DS are not meeting PA guidelines; 4 studies found intensity levels decline with age. Three studies reported children with DS engage in significantly less vigorous PA than control groups. Determination of intensity levels varied, limiting additional comparisons.

Conclusions: Children with DS engage in less PA than peers developing typically and are not meeting PA guidelines across age groups, increasing risk for numerous health conditions secondary to decreased activity.

Recommendations for Clinical Practice: Promotion of more appropriate levels of PA and elimination of barriers to participation in PA are important for individuals with DS.

This systematic review of literature analyzed accelerometer use to measure physical activity in individuals with Down syndrome.

Division of Physical Therapy, Department of Orthopaedics, Duke University, Durham, North Carolina.

Correspondence: Bianca Fox, MS, SPT, Doctor of Physical Therapy Division, Duke University, 2200 W Main St, Durham, NC 27705 (bianca.fox@duke.edu).

At the time this article was written, Bianca Fox, Gwendolyn E. Moffett, Clara Kinnison, and Grace Brooks were students in the Doctor of Physical Therapy Program at Duke University, Durham, North Carolina.

Supplemental digital content is available for this article. Direct URL citation appears in the printed text and is provided in the HTML and PDF versions of this article on the journal's Web site (www.pedpt.com).

The authors declare no conflicts of interest.

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INTRODUCTION

Down syndrome (DS), defined by the presence of part or all of a third 21st chromosome, is the most common chromosomal congenital disorder in the United States, affecting 1 out of 790 infants.1 Common characteristics include cognitive impairments, distinctive facial features, short stature, and hypotonia.2 Children born with DS are at increased risk for heart defects, visual and hearing impairments, and childhood obesity, among numerous other health conditions.2 , 3 In addition, the natural history of individuals with DS typically includes delays in gross motor development accompanying low muscle tone, ligamentous laxity, and excessive flexibility, with development of abnormal secondary patterns of alignment and movement at the foot, ankle, knee, and hip.2 , Down syndrome. Am J Ment Retard. 2001;106(5):470–478. doi:10.1352/0895-8017(2001)106<0470:AOAKDW>2.0.CO;2.','400');" onMouseOut="javascript:ImageWrapperControl_ImageMouseOut();">4 , 5 Subsequently, children's ability to engage and participate in physical activity (PA) may be decreased,3 increasing their risk for the progression or exacerbation of associated health conditions.

Regular PA is important for promoting overall health and well-being across the lifespan. Benefits of regular PA in pediatrics include improvement of cardiorespiratory fitness, development of a strong musculoskeletal system, and reduced risk of developing health conditions such as heart disease, cancer, type 2 diabetes, high blood pressure, osteoporosis, and obesity.6–9 The 2008 US Physical Activity Guidelines for Americans recommends children and adolescents aged 6 to 17 years should engage in 60 minutes or more of PA each day.10 Although there are currently no specific PA guidelines for children with DS, recommendations for individuals with intellectual disabilities include a large variety of recreational activities dispersed throughout the day.10

Wearable activity monitors such as accelerometers are one way to objectively measure PA. Using sensors that measure the acceleration of moving objects, accelerometers attached to certain points, such as the wrist, hip, or ankle, can capture data reflecting the intensity and frequency, and in turn energy expenditure, of human movement.11 When compared with subjective assessments, the proven reliability and validity of the objective data obtained from accelerometer measurements for children with DS makes it the preferred method of tracking PA in this population.3

With the exception of one review published in 2013 that provides a general overview and underscores the importance of physical fitness and activity levels in pediatric populations with DS,3 there are no reviews that specifically use activity monitors to examine the PA levels of children with DS. Noting the need for further research in methodologies to determine PA levels,3 such work could help guide future research and clinical practice. The purpose of this systematic review is to analyze the use of accelerometers to measure PA in pediatric populations diagnosed with DS.

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METHODS

Search Strategy

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines12 and registered with PROSPERO (registration number CRD42017075511). A comprehensive search strategy was performed in August 2017 in collaboration with university librarians trained in systematic review methods. PubMed, Embase, and CINAHL were searched for studies published through July 2017 (Supplemental Digital Content 1, available at: http://links.lww.com/PPT/A230). Relevant studies and systematic reviews were also hand searched by going through the reference lists of all articles included after the screening of titles and abstracts.

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Selection Criteria

Search results were limited to studies published in English; editorials, letters, comments, and case reports were excluded. Titles and abstracts were independently screened by 2 reviewers (87.8% agreement, κ = 0.75), with full-text articles reviewed independently by 2 additional reviewers (93.3% agreement, κ = 0.83). Articles were included using the following criteria: (1) participants were 21 years or younger and diagnosed with DS; (2) activity monitors were used for data capture; and (3) PA was reported in terms of frequency, duration, or intensity. Discrepancies were resolved through discussion between reviewers.

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Data Extraction and Assessment of Methodological Quality

Data from included studies were extracted, but not manipulated, independently by 1 reviewer using a standardized form developed for this review. Extracted data included study population size, demographics of participants, activity monitor used and measurement procedure, comparison group and/or PA guidelines, and results. A second reviewer confirmed accuracy of data extraction.

Quality of included studies was independently evaluated by 2 reviewers (81.7% agreement, weighted κ = 0.66) using a modification of the Downs and Black tool, a tool to quantify risk of bias in articles on randomized and nonrandomized control trials. The original tool includes 27 items covering the following domains: reporting, external validity, internal validity (bias and confounding), and power,13 and has been identified as among the best tools for evaluating the quality of nonrandomized control trials.14 For our purposes, we omitted the power item (item 27) based on inconsistencies in how, if at all, it is scored in other studies using the tool, and concerns in literature about using the item due to its ambiguity.15 Separate scores were obtained for each section, and a total score was determined out of a possible 27 points for our modified version. Based on the total score, studies were rated as “excellent” (24-27 points), “good” (19-23 points), “fair” (14-18 points), or “poor” (≤13 points) based on the numerical rating scale from O'Connor et al,16 adjusting down 1 point from the maximum total to account for the omitted item. Any discrepancies between the 2 reviewers were resolved through discussion, with inclusion of the 4 reviewers when necessary.

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RESULTS

The full search strategy identified 74 articles after duplicates were removed. Title and abstract screening excluded 44 articles. Of the 30 articles obtained for full review, 22 were excluded. Reasons for exclusion included providing only a general overview on PA levels, examination of a separate intervention rather than purely measuring PA levels, the use of accelerometer data from 1 initial study17 for analysis of possible health correlations, and having a population that did not solely focus on patients with DS. This left a total of 8 studies for final review (Figure); 5 were cross-sectional studies,17–21 1 was a pilot study,22 and 2 were longitudinal studies.23 , 24 The articles selected for full review all reported results on PA levels measured by wearable accelerometers and had a clearly defined population of children with DS. Table 1 summarizes the data extracted from the included studies.

Fig

Fig

TABLE 1

TABLE 1

The age range of participants encompassed 3 months to 20 years, with a higher proportion of males to females. All studies excluded participants who had other physical disabilities or health conditions that would impact PA levels. Four studies used children developing typically as a comparator.19–21 , 24 Six studies also compared participant outcomes to PA guidelines of at least 60 minutes of moderate to vigorous PA per day17–20 , 22 , 23; 1 study used a guideline of 30 minutes of moderate PA per day.21

When tracking activity levels, 7 studies used accelerometers for activity tracking over 7 days17–23 while 1 study tracked activity for 48 hours once a month over the span of 4 months.24 One study used the Actical worn on the hip set to 15-second epoch18; 2 studies used the ActiGraph worn on the lower back set to 2-second17 and 10-second23 epochs, respectively; 2 studies used the ActiTrainer worn on the hip set to 15-second epochs19 , 20; 1 study used the RT3 worn on the waist set to 1-minute epoch22; 1 used the Actitrac worn on the waist set to 30-second epoch21; and 1 study used the Actiwatch worn on the ankle set to 15-second epoch.24 Participants in all studies were instructed to wear the activity monitors for all activities except for water-based activities, as well as for sleeping in 6 studies. Requirements for inclusion in data analysis ranged from no defined minimum wearing time to at least 8 to 10 hours per day and for at least 3 to 6 days. Cut points for determining intensity of activity varied greatly across all studies.

Results from the assessment of quality are shown in Table 2. Most of the studies (5 of the 8) fell into the “fair” category,18 , 20 , 22–24 with 2 rated as “good”17 , 21 and 1 as “poor.”19 Studies tended to be strong in the reporting category, but were weaker in the internal and external validity categories. In particular, studies tended to lose points due to issues with blinding (participants could not be blinded to the fact that they were wearing an accelerometer, and the act of wearing it may have influenced their activity level), recruitment (samples were not likely to be representative), and confounding (lack of randomization).

TABLE 2

TABLE 2

Table 3 presents results in more detail. The overarching results of the full-text review supported that children with DS are not meeting the recommended PA guidelines of at least 60 minutes of moderate to vigorous PA daily. Four of the studies, including the longitudinal studies, found younger children with DS engaged in more PA of higher intensity than older children.17 , 18 , 23 , 24 In 6 of the 7 studies that investigated PA guidelines, the percentage of participants with DS meeting activity guidelines ranged from 0% to 43%.17–20 , 22 , 23 The study by Whitt-Glover et al21 reported up to 93% of children participating in at least 60 minutes per day of moderate PA and 40% in vigorous PA, but this included both children with DS and children developing typically and the cut points used were much lower than those of the other studies. Two studies found that no participants engaged in vigorous PA of 20 continuous minutes.21 , 22 The longitudinal study by Izquierdo-Gomez et al23 also found that those participants who met PA guidelines at the baseline measurement showed a greater decline in activity levels over the 2 follow-up years while those participants who did not meet guidelines at baseline maintained their activity levels. No significant difference was found between activity levels during the week versus weekend or between during school versus after school.17 In addition, the only differences found between males and females was males were more active than females during the weekend17 and engaged in more vigorous PA over a 2-year follow-up.23 For those studies with control groups, 3 found that children with DS engaged in less vigorous PA,19–21 and 2 found that children with DS engaged in more light PA and less sedentary and moderate PA than the children in the control group.19 , 20 One study found that infants with DS, while as active as their peers who were developing typically, engaged in low intensity activities for longer periods during the day at 3, 4, and 6 months of age and had different motor activity patterns from 4 to 6 months of age.24

TABLE 3

TABLE 3

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DISCUSSION

This review provides objective information on the PA levels of children with DS. Although there are limitations due to the nature of the included studies, it provides important insight into the current activity levels that can inform future research and efforts to increase PA levels of children with DS.

Overall, studies found that children with DS are not reaching recommended guidelines of 60 minutes of moderate to vigorous PA each day. In addition, studies found that PA, particularly more intense PA, tended to decrease with age while sedentary time tended to increase. Furthermore, in studies that included a control of children with typical development, children with DS tended to engage in more light-intensity PA than moderate or vigorous PA as compared with the controls developing typically. This is concerning, not only because children with DS are at risk for health conditions for which PA can have a positive effect (eg, obesity),6 , 7 but also because decreased physical fitness in this population has been found to result in functional activity impairments.25 Individuals with DS spent less time in a sedentary state than controls who were developing typically. Although studies did not provide a reason for this trend, several possibilities exist. For example, controls developing typically may be spending more time seated completing school and homework. Alternatively, individuals with DS may be more restless, given that individuals with DS have higher rates of psychiatric and behavioral disorders, including attention-deficit hyperactivity disorder, than other children.2 , 26 As individuals with DS are inclined to move, but are engaging in less moderate to vigorous PA, it is important to investigate barriers to participation in PA and to consider efforts to promote increased levels of higher intensity PA.

The control group participants were not meeting PA guidelines. This agrees with a study that examined activity levels of US youth with accelerometers,27 and the most recent US Report Card on Physical Activity for Children and Youth.28 This supports a growing awareness that a further increase of PA and a decrease of barriers to PA participation may need to be incorporated into the daily lives of all children.

While this review provides insight into the PA levels of children with DS based on objective, accelerometer data, there are limitations to the review that impact conclusions. Included studies varied in accelerometers and epochs used as well as the cut points for activity intensity levels. Using different epochs and different cut points can result in different classifications of activity level. Furthermore, cut points used in these studies often were based on cut points suggested for children developing typically. Given that children with DS can have related cardiovascular and musculoskeletal impairments,2 , 3 these cut points may not reflect the true activity intensity level for children with DS, possibly resulting in an underestimation of time engaged in moderate to vigorous PA. That is, children with DS may be engaging in more intense activity than children developing typically at the same accelerometer counts because impairments associated with DS may make movement less efficient.3

In addition to these limitations based on data collection and analysis, there are limitations related to influences on activity due to wearing the accelerometer. The accelerometers provide an objective measure of PA throughout the day, reducing the risk of bias associated with self-report measures. However, children (and their parents) knew their activity was being monitored, so this may have altered their normal activity levels leading to bias. If children are bothered by the accelerometer, they may engage in less activity. Conversely, knowing that activity is being monitored, children may make more effort to engage in PA during that time and/or their parents may encourage more activity during that time. In this case, PA levels may be overestimates of habitual activity.

Finally, recruitment efforts in these studies may have resulted in study populations that were not representative of the general DS pediatric population. In particular, parents who have a strong belief in the importance of PA and/or who encourage their children to engage in higher levels of PA may have been more inclined to volunteer for these studies. No indication was given as to what, if any, prior physical therapy and other rehabilitative services the children may have received. It is conceivable that those children who received more services before the studies might have higher levels of PA. As a result, these studies may have overestimated the amount of PA typical of children with DS in the broader population. There may have been overlap in participants in some included studies, thus affecting representativeness. The Izquierdo-Gomez et al studies,17 , 23 due to the longitudinal design, reported on PA levels for the same cohort at different time points. In addition, the Matute-Llorente et al studies,19 , 20 given their similar timeframe and recruitment strategies, may have reported on data from the same cohort of participants. However, it is not clear from the articles whether these were in fact 1 cohort or 2 separate cohorts. As a result, although 8 studies are included, they may only represent 6 distinct groups of participants, which could further limit generalizability.

The limitations described earlier are important to consider and suggest areas for further research. While PA may have been overestimated due to the nature of wearing a device to monitor activity and/or the representativeness of the sample, overall, children with DS were not meeting PA guidelines. However, activity level cut points may have underestimated the actual intensity at which these children engaged in activity. Appropriate cut points should be determined for children with DS to ensure that conclusions about the time spent in moderate to vigorous PA are accurate. Despite these limitations, these studies suggest that efforts should continue to promote more PA in children with DS and to reduce barriers for this population to engage in PA so that they can build healthy activity habits that will carryover as they age.

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CONCLUSIONS

The results of this review suggest children with DS are engaging in less PA than their peers who are developing typically and are not meeting PA guidelines across age groups, with intensity of activity levels declining as children enter adolescence. However, the majority of studies only had “fair” quality and varied greatly in determination of intensity levels of activity, indicating a need for further research. Regardless, noted decline and lack of more vigorous PA poses functional and general health risks for this population. Areas for future research include validation and standardization of cut points for children with DS and analysis of characteristics of activity levels, both throughout the day and across the lifespan. Future research should examine the effect of early physical therapy and explore the potential benefits of physical therapy across the lifespan on PA and on neuromusculoskeletal issues characteristic of DS known to affect PA (eg, alignment, posture, muscle tone, strength, endurance, and cardiorespiratory fitness). Focused study of times of increased risk and vulnerability and times of transition characterized by decreased PA and participation will be important, as well as studying how increasing PA impacts the health and well-being of children with DS.

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ACKNOWLEDGMENTS

We would like to thank Leila Ledbetter, MLIS, for her assistance with this project.

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Keywords:

accelerometer; Down syndrome; pediatric; physical activity

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