What is actigraphy? Discover how it can be applied to different areas of medicine
By understanding how actigraphy works, it is possible to apply the method in several areas.
Actigraphy (or actimetry) is the method of monitoring activity-rest cycles. Through it, constant non-invasive data capture occurs, as well as the compilation and processing of information aimed at the analyses of the pace of sleep/wakefulness over long periods of time, identifying phases of activity and rest.
This is how we practically and directly define actigraphy. However, we think it is important to go deeper into the subject, and we will do so throughout this article by detailing the definitions, getting to know new technologies and presenting answers to questions such as:
- How does actigraphy work?
- What are the advantages of actigraphy?
- Are there other applications of actigraphy besides sleep medicine?
- How do actigraphs work nowadays?
The day and night cycle
It is common for most living beings to continuously interact with a constant period of environmental change: the cycle of day and night, which results from the rotation of the Earth.
This phenomenon had a strong influence on the evolutionary process so that a series of physiological and behavioral oscillations are expressed synchronously whilst the interaction with said periods took place.
The consequences of the interaction of day and night cycles are also observed in humans, where physiological events such as a decrease or increase in respiratory rate, hormone release, thermoregulation, among others, present oscillation in periods of approximately 24 hours and can be analyzed longitudinally, so that it is possible to get a complete overview of what happens in the human body over the course of a day.
The importance of actigraphy resides in the possibility of a full understanding of this overview
How does actigraphy work?
Actigraphy is performed through an actimeter, a device that normally looks a lot like a watch and is commonly used on the individual’s non-dominant arm.
The equipment records movement with the use of an accelerometer. The measurement normally takes place every minute. Modern actigraphs have other sensors, such as temperature and light, among others, that can contribute to the analysis of sleep and circadian rhythm.
The actigraph is, essentially, responsible for capturing the data used to:
- Detect the existence of sleep disorders and circadian rhythmicity, assessing sleep quality, estimate time spent in bed, detect episodes of sleep during the day, as well as estimate levels of physical activity and stability of circadian rhythm in the individuals’ routine.
- Monitor movements from actigraphy for later use in studies in the field of sleep medicine, psychiatry, occupational medicine, behavioral psychology, among other areas of knowledge in which the analysis of circadian rhythmic expression has a fundamental role for deeper understanding of the disorders.
Over the years and after several technological and scientific innovations, today’s actigraphs can provide information on circadian rhythm and sleep parameters via data generated through detailed analyzes by pre-established parameters:
✓ Exposure to light during the day;
✓ Expression of the rhythmicity of body temperature;
✓ Events during sleep stages;
Thus, actigraphy plays an important role in gathering information and helping make more robust and assertive diagnoses.
The circadian rhythm
Circadian rhythm (or circadian cycles) is defined as the biological cycles that have an approximate duration of 24 hours.
The interaction between natural environmental information (light/dark cycle) and the individual’s circadian oscillating system plays an essential role in regulating the body’s various physiological and behavioral events.
The most commonly analyzed events are:
– Cell renewal;
– Protein synthesis;
– Anti-inflammatory activity;
– Temperature control;
– Sleep-wake states.
It is in the last event that most people notice that the expression of rhythm occurs around a 24-hour duration.
From the monitoring of physiological and behavioral fluctuations throughout the day, it is possible to produce a temporal organization taking several parameters into account, including the interaction with environmental events.
The chart at the beginning of this section is an example of how the internal temporal organization of different circadian rhythms can occur. It is possible to identify at what time of the day certain physiological states stand out and, through the analysis of these states, to indicate possible dysfunctions that may point out physical and/or psychological health problems.
The advantage of actigraphy over other methods
Many of these events, which have the circadian expression as a characteristic, can only be monitored using specific behavioral testing protocols, as well as being conducted invasively and within a laboratory setting.
The greatest advantage of actimetry is that it provides information on people’s habits in their natural environment, taking place for a long period of time in a non-invasive approach. Through the actigraph, it is possible to extract data that support or discards the previously raised hypotheses, in addition to other information that make up a more complete diagnosis.
Clinical application of actigraphy
Known for its application in the field of sleep medicine and chronobiology, the use of actigraphy can be applied in other areas of research and medicine, providing data for diagnosis and clinical treatments in other fields, as shown by a series of scientific articles published in several countries found in the Pubmed database.
The following are some areas of medicine that have used actigraphy:
– Actigraphy and Cardiology
An article in the New York Heart Classification describes the use of the actigraph in 35 elderly people with Type I to III heart failure. The patients used the device on the non-dominant wrist for 9 months and, through the information collected, it was possible to verify a lack of disposition with less movements and more circadian changes. Additionally, the authors mention that the lack of daily disposition is a predictor for a greater number of hospitalizations.
– Actigraphy and Chronobiology
Several studies in the chronobiology field use actigraphs to observe the expression of circadian rhythmicity. It is possibly one of the areas in which the use of actigraphy occurs routinely. Through actigraphy, it is possible to detect changes in the expression of circadian rhythmicity in treatments, monitor the activity-rest rhythm of shift workers, identify rhythm disturbances, as well as studies that identify seasonal fluctuations in behavior.
A recent study entitled “Sleep misalignment and circadian rhythm impairment in long-haul bus drivers under a two-up operations system”, which evaluates bus drivers through actigraphy, observed that high-risk work routines have a negative effect on the expression of circadian rhythmicity associated with sleep fragmentation.
– Actigraphy and Sleep Disorders
The study “Behavioral correlates of sleep-disorder breathing in older men”, using data obtained through actigraphy and polysomnography, followed 2849 men over 65 years with untreated sleep apnea. It was observed that the total sleep time evaluated by the actigraphs was associated with daytime sleepiness, poor sleep quality and disturbances during sleep.
In another study, entitled “Comparison of sleep quality assessed by actigraphy and questionnaires to healthy subjects”, the authors identified that healthy individuals presented an association of parameters commonly used for the analysis of circadian rhythmicity with self-declared sleep quality.
– Actigraphy and Chronic Pain Pictures
In the pilot study “Objective and subjective assessment of sleep in chronic low back pain patients compared with healthy age and gender matched controls”, the sleep of people with chronic low back pain was quantitatively and qualitatively evaluated, where 15 of them had symptoms and another 15 consisted in a control group.
Objective data (quantitative) were obtained through actigraphy and subjective data (qualitative) were collected through a questionnaire. It has been observed that in individuals with chronic low back pain sleep quality is worse and is associated with increased daytime sleepiness.
– Actigraphy and Women’s Health
The study “Effect of external motion on correspondence between infant actigraphy and maternal diary” was carried out with 112 women and aimed to objectively measure the impact of sleep fragmentation and its influence on postpartum depression. Through the use of actigraphy, it was found that sleeping at least one hour during the day indicated a correlation with lower rates of postpartum depression.
– Actigraphy and Neurology
The actigraph was applied to patients who had difficulty performing polysomnography all night, such as, for example, people with dementia. Actigraphy was also used to collect data for a report entitled “Melatonin fails to improve sleep or agitation in doubleblind randomized placebo-controlled trial of institutionalized patients with Alzheimer disease”, aiming the improvement of the expression of circadian rhythmicity in patients with probable Alzheimer’s disease diagnosis, as well as the analysis of the effects of melatonin on their sleep.
However, from the actigraphy analysis, it was possible to observe that there were no differences in sleep and rhythm parameters, which perhaps could be affected by the use of questionnaires.
– Actigraphy and Psychiatry
The study “Anxiety symptoms and objectively measured sleep quality in older women”, carried out with 3040 elderly women (86 years old on average), aimed to establish a correlation between sleep patterns and anxiety.
In the methodology, the actigraph was used to collect data on total sleep time, sleep efficiency, latency and other parameters. Poor quality sleep and greater sleep fragmentation has been observed in older women and is not associated with other types of behavioral disorders.
In the article “Activity/rest rhythm of depressed adolescents undergoing therapy: case studies”, teenagers with depressive disorders were observed for 13 consecutive weeks with the help of actigraphy. A connection between high scores on the CDRS-R (questionnaire that evaluates depression symptoms) and a steadily decreased activity-rest rhythm was perceived.
Combined with other methods, tests and equipment, or through its exclusive use, it is clear that actigraphy has proven to be of great value in improving data capture, diagnostics and hypothesis validation in various fields of medicine and health sciences, both in the clinical and scientific fields, guiding professionals from different areas to prescribe more assertive and efficient treatments.