Elsevier

Sleep Medicine Reviews

Volume 16, Issue 5, October 2012, Pages 463-475
Sleep Medicine Reviews

Clinical review
Use of actigraphy for assessment in pediatric sleep research

https://doi.org/10.1016/j.smrv.2011.10.002Get rights and content

Summary

The use of actigraphs, or ambulatory devices that estimate sleep–wake patterns from activity levels, has become common in pediatric research. Actigraphy provides a more objective measure than parent-report, and has gained popularity due to its ability to measure sleep–wake patterns for extended periods of time in the child's natural environment. The purpose of this review is: 1) to provide comprehensive information on the historic and current uses of actigraphy in pediatric sleep research; 2) to review how actigraphy has been validated among pediatric populations; and 3) offer recommendations for methodological areas that should be included in all studies that utilize actigraphy, including the definition and scoring of variables commonly reported. The poor specificity to detect wake after sleep onset was consistently noted across devices and age groups, thus raising concerns about what is an “acceptable” level of specificity for actigraphy. Other notable findings from this review include the lack of standard scoring rules or variable definitions. Suggestions for the use and reporting of actigraphy in pediatric research are provided.

Introduction

Actigraphy is an objective, non-intrusive method for estimating sleep–wake patterns using activity-based monitoring. The use of actigraphy in research has gained significant popularity over the past 20 years, to the extent that the recent growth in published research studies that used actigraphy have outpaced studies that used polysomnography (PSG).1 Actigraphy can be a particularly valuable methodology for use among pediatric populations, where the common reliance on parental report alone may limit the range and accuracy of information about children's sleep. Consistent with the growth of actigraphy use across sleep research domains reported by Sadeh,1 there has also been significant growth in the report of actigraphy specific to pediatric studies (Fig. 1), with the number of studies published in 2010 alone (n = 41) similar to the total number of studies published from 1991 to 2001 (n = 38).

The 2007 American Academy of Sleep Medicine practice parameters state that, “Actigraphy is indicated for delineating sleep patterns, and to document treatment responses in normal infants and children (in whom traditional sleep monitoring by polysomnography can be difficult to perform and/or interpret), and in special pediatric populations”.2 Despite this recommendation and the growth in the number of studies that utilize actigraphy, there are currently no practice standards regarding recording parameters and scoring of the recorded actigraphy signals. Thus researchers and clinicians have little guidance in the use of this technology with little consistency across the body of literature reporting actigraphy results. This lack of uniformity has resulted in the inability to compare data values across studies. Further, despite the common use of these devices, no normative values are available for pediatric populations.

Another area of particular concern and utmost importance is the validity of actigraphy as a measure of sleep–wake patterns among children and adolescents of all ages. Many studies discuss the validity of actigraphy compared to PSG, but then cite studies validated on adult samples.3, 4, 5 Actigraphy output provides valuable information about activity levels that are ideal for visual analysis, which is useful for evaluating clinical treatment efficacy or to corroborate parental report of child sleep. However, actigraphically measured sleep estimates among pediatric samples (e.g., total sleep time or wake after sleep onset) should only be used when the recording device and particular sleep value are established as valid in comparison to a ‘gold standard’ measure such as PSG or direct observation.

Correlation statistics are often used to evaluate the validity of actigraphy when compared to a gold standard like PSG. However, correlations alone are not an appropriate way to validate these devices. A perfect correlation can be found between any two instruments, even if they have widely divergent measurement scales, as long as both measures increase at the same proportional rate. Some validation studies have relied only on correlation analyses, while others have overemphasized high sensitivity and underemphasized low specificity. Sensitivity and specificity bear further explanation because they are the most appropriate statistical method for validity assessment.

Sensitivity and specificity are most commonly used in the biomedical field for determining the quality of a novel diagnostic instrument. Sensitivity describes how accurately an instrument identifies people with a disorder (“true positive” cases); the more people who are inaccurately identified as not having the disorder (“false negative” cases), the less sensitive the instrument. On the other hand, specificity describes how accurately an instrument identifies people who do not have the disorder (“true negative” cases); the more people inaccurately identified as having the disorder (“false positive” cases), the less specific the instrument.

An ideal test accurately identifies 100% of both positive cases (is highly sensitive) and negative cases (is highly specific). When it comes to actigraphy, researchers have established a convention of considering sensitivity to be the proportion of epochs scored as sleep using polysomnography that are accurately identified as sleep by actigraphy. Specificity, on the other hand, is the proportion of polysomnography-scored wake epochs accurately identified as wake by actigraphy. An actigraph, or algorithm, that incorrectly scores sleep as wake has low sensitivity, and an actigraph, or algorithm, that incorrectly scores wake as sleep has low specificity. For example, if an actigraph scores an entire sleep period as sleep, it would be 100% sensitive at the expense of poor specificity in identifying wake during the sleep period. Both sensitivity and specificity are inherently important since the incorrect scoring of sleep or wake can result in under or overestimates of reported sleep variables (e.g., total sleep time, wake after sleep onset).

Thus, examinations of sensitivity and specificity, and the relation between the two (represented by the “likelihood ratio”), are necessary for establishing the extent of actigraphy's validity. Another assessment technique commonly used to examine instrument validity is the Bland–Altman concordance technique.*6, 7 This approach provides a visual representation of agreement by plotting the new method against the gold standard. The difference between the measures for each participant are fitted to lines that represent the ideal (no difference), plus either standard deviations or time discrepancies to show each participant's deviation from the ideal.

For a more detailed description of validation and reliability issues pertaining to use of actigraphy, the reader is referred to several comprehensive reviews.*1, 8, 9

The purpose of this paper is to provide a comprehensive review and synthesis of the research literature that used actigraphy as a measure of sleep–wake patterns or circadian rhythms among pediatric populations (ages 0–18 years, inclusive). This review highlights areas that should be considered in the design, execution, and report of sleep–wake variables in pediatric research studies that utilize actigraphy. In addition, a thorough description of the existing research that has examined the validity of these devices is provided. It is important to note that the purpose of this paper is not to provide recommendations about which brand to use or specific ways to improve existing technologies. Further, the clinical utility of actigraphy is beyond the scope of this review. Rather we objectively report on the use of existing technologies, as well as provide evidence-based recommendations for the proper use and reporting of actigraphy in pediatric research.

Section snippets

Methods

A literature search was conducted using the Cumulative Index to Nursing and Allied Health (CINAHL), PsychInfo, and Pubmed. Search terms were (actigraph* or accelerometer or actimeter or actiwatch) and (newborn or infant or toddler or preschool* or child or children or adolescent* or adolescence* or youth or pediatric or premature infant*) and (sleep or rest or circadian). In addition to the electronic search, reference lists from the identified articles and other review papers were reviewed for

Study sample

Using the previously described search terms, 491 abstracts for papers published through December 2010 (including electronic publications ahead of print) were identified. An additional 15 articles were identified through a review of reference lists of eligible articles or review papers. Based on a review of these 506 abstracts, 269 papers met inclusion criteria for review. An additional 41 papers were excluded during full paper review because they included primarily adults (n = 10), the outcome

Use of actigraphy in pediatric sleep research

The purpose of this review was to describe methodological issues with actigraphy in pediatric sleep research. Although actigraphy is by no means a “gold-standard” measure of sleep, the rapid growth in its use over the past 20 years in pediatric research and the sheer volume of studies published that utilize actigraphy demonstrate the importance of these devices as an estimate of sleep–wake patterns. Despite the growth in actigraphy use, this review highlights several notable concerns for how

Considerations for the use of actigraphy in pediatric sleep research

A comprehensive review of the methodological challenges and considerations for the general use of actigraphy can be found in a recent review of actigraphy use with adult populations by Berger et al.32 The following provides a highlight of these considerations specific to pediatric sleep research.

Concluding remarks

Actigraphy has become a central part of pediatric sleep research in the past 20 years. While there are a number of benefits to actigraphy, researchers and consumers of the literature also need to be aware of the limitations and threats to validity, most notably poor specificity to detect wake after sleep onset, how artifact influences results, and the lack of consistency in terms of scoring rules and reported variables. Although we have provided some suggestions based on this review, the field

Conflict of Interest Statement

The authors have no conflicts of interest to disclose.

Practice points

  • 1.

    Actigraphy provides a non-intrusive, cost-effective way to objectively estimate pediatric sleep–wake patterns for an extended period of time within the child's natural environment.

  • 2.

    The use of actigraphy also requires concurrent sleep diaries in order to identify artifact and to corroborate or guide identification of sleep periods on actigraphy output.

  • 3.

    The selection of devices, scoring algorithms or sensitivities, and device

Acknowledgments

We thank Devon Ambler for her assistance with the references. Support for this manuscript was provided by K23 MH066772.

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    Tel.: +1 304 293 2001x610; fax: +1 304 293 6606.

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    Tel.: +1 412 246 6943.

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    Tel.: +1 215 662 3189.

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    Present address: University of Pennsylvania, PA, USA.

    *

    The most important references are denoted by an asterisk.

    Overlapping studies.

    i

    Studies that include children with autism spectrum disorders.

    k

    Studies that include children with intellectual disorders.

    l

    Studies that include children with chronic medical illnesses.

    m

    Studies that include children with ADHD.

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