subject: Ambulatory monitoring of sleep disorder [print this page] Ambulatory monitoring of sleep disorder Ambulatory monitoring of sleep disorder
AbstractBackground: Behavioural and functional activitymonitoring has a long history in sleep research. The term"Actigraphy" refers to methods using computerized wristwatch-size devices (generally placed on the wrist, but also onthe ankle or trunk) to record the movement it undergoes.Collected data are displayed on a computer and analyzed forchange in rhythm parameters that in turn provide an estimateon wake-sleep parameters (such as total sleep time, percent oftime spent asleep, total wake time, percent of time spentawake and the number of awakenings). Actigraphy providesa useful, cost-effective, non-invasive and portable method forassessing specific sleep disorders. The present review is anamalgam of current knowledge with proposed clinicalapplication and for research of actigraph. Conclusion:Actigraphy cannot stand alone as a diagnostic tool for allclinical groups. Particularly so with those diagnosed withsleep disorders with significant motility or long catatonicperiods of wakefulness during sleep.IntroductionPatterns in human body movements (activity) are ofinterest for many scientific disciplines. Application ofaccelerometers using miniature motion sensors to study themacro (gross) and micro- (barely discernible) activitiesassociated with human motion has been termed actigraphy.Advances in accelerometry technology resulted in devicesthat miniaturize these monitoring systems to the size of adigital wristwatch. Nowadays, the terms actigraph andactigraphy have been widely applied in sleep research. In thisreview, the term actigraph will refer to the sensor, whereaswrist-mounted actigraphy will refer to the use of the sensoron the wrist platform.Actigraphy has been broadly used to study sleep/wakepatterns for over 25 years. Although polysomnography (PSG)is the gold standard for sleep studies, the advantage ofactigraphy over traditional polysomnography lies in itscontinuous ambulatory recording for a day, to weeks or evenlonger. Since its conception in 1920s, actigraphy wasdeveloped to objectively measure and quantify sleep patternsbased on body movements. For example, Szymansky in 1922constructed a device that was sensitive to the gross bodymovements of subjects while lying in bed.1 However, theadvent of electroencephalograph (EEG) recording along withthe development of EEG-based polysomnographic standardsfor the scoring of sleep stages resulted in a shift, distancingthis approach from movement-based measurements of sleep.2A resurgence of interest in the use of movement-basedmeasurement of sleep occurred when wrist-mountedaccelerometry was developed in the 1970s and 1980s at theWalter Reed Army Institute of Research (AIR) and theNational Institutes of Health (NIH). Wrist-mountedaccelerometers were based on technological advances that,for the first time, made long-term portable measurement andrecording of movement data feasible.3In 1995, Sadeh and colleagues under the auspices ofthe American Sleep Disorders Association (now called theAmerican Academy of Sleep Medicine, AASM), reviewedthe literature pertaining to the role of actigraphy in theevaluation of sleep disorders. They concluded that actigraphyprovided useful information and that it may be a "costeffective method for assessing specific sleep disorders butmethodological issues have not been systematicallyaddressed in clinical research and practice".4 Based on thattask force's report, the AASM Standards of PracticeCommittee in 1995 concluded that actigraphy was notindicated for routine diagnosis or for assessment of severityor management of sleep disorders, but might be a usefuladjunct approach for diagnosing insomnia, circadian rhythmdisorders or excessive sleepiness.5Nowadays, wrist-mounted actigraphs have movementdetectors and sufficient memory to record for up to severalweeks. Analysing programmes are to derive levels ofactivity/inactivity, rhythm parameters and sleep/wakeparameters.6In addition, PubMed - a service provided by theUS national library of Medicine and NIH - shows over 913citations using actigraphy or actigraph with human subjects,of which 677 are investigating adult individuals (age 19 andover), of which 8 are reviews. Since new devices, sleep-wakescoring algorithms, and operating procedures are constantlydeveloped and up-dated, in this review, we have chosen toelide discussing technical merits of the various instruments,modes of operations, and specific brand names. Furthermore,we position this paper in the light that no consensus ofopinion has been reached among clinicians and researchers asto which device or algorithm is best. Additionally
