Actigraphy, also called actimetry, is the measurement of body movements. This is a measurement taken at the wrist to determine activity levels during sleep and wakefulness. This is a different method of measuring activity than polysomnography. Polysomnography is only suitable for laboratory conditions and has fewer practical applications than actigraphy. This is due to its focus on measuring sleep stages. It does this through EEG (electroencephalograms), EMG (electromyograms) and EOG (electro-oculography). These measure the electrical activity of the brain, muscle activity in various parts of the body, and eye movement, respectively. Studies show that actigraphy is as effective as polysomnography in measuring sleep-wake activity.
An actimeter is a device worn on the wrist that performs actigraphic measurements. It measures periods of activity and rest. Actimeters are worn day and night. They provide insight into circadian rhythms. A circadian rhythm, commonly known as the “biological clock”, is a 24-hour cycle that our bodies align to in order to function properly.
Circadian rhythms are essential for telling our biological processes when to start and when to end. They allow us to maintain healthy functional capacity. This includes the hormonal releases and inhibition of melatonin and cortisol that cause us to sleep and wake up, our reception to blue light levels related to energy release and digestion, and most importantly, our cognitive and physical functions. Actimeters measure these rhythms so we can see how strong they are and how healthy a person is.
Polysomnography is cumbersome, expensive, and has few practical real-world applications. Actigraphy is much more accessible, discreet and profitable. It measures activity over long periods of time and builds a complete picture of changes in rhythms over time. It is extremely sensitive – the Vivago Care Watch is over 96% polysomnography sensitivity.
But polysomnography is not specific in what it measures, it only tracks activity and rest. This means it is exceptional for measuring daytime and nighttime activity levels. But it’s not descriptive of why people’s circadian rhythms change over time. Given the complexity of human biology and environmental and health factors, the latter is impossible to achieve at this stage. Fortunately, trained medical professionals can use actigraphy to see if a patient’s health is improving or declining.
Actigraphy has played a prominent role in research on sleep performance in different environments. Studies have shown that 40-70% of older people have sleep problems and sleep deprivation is common in nursing homes. Research also shows that recovery times decrease when good quality nighttime sleep occurs and daytime sleep is avoided. This leads to better physical and mental functioning.
Many neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease have the same mechanistic origins as abnormal sleep. By measuring sleep patterns, it is possible to predict cognitive decline and identify potential neurodegenerative disorders. This allows professionals to act quickly to manage them.
Measurements taken by an actimeter can be plotted on a graph to show activity over time. These are called “activity curves” or “activity graphs” and give an overview of long-term condition changes.
It is easy to see how an individual behaves and whether their rhythms are strengthening or weakening. A circadian rhythm score can be produced. This is done by dividing the average nighttime activity by the average daytime activity. The scores obtained show the consistency and strength of the circadian rhythm. A score close to “0” shows a strong circadian rhythm, and a score close to “1” or above shows a weak circadian rhythm.
Below are examples of activity curves showing strong and weak circadian rhythms.
A strong correlation exists between the strength of circadian rhythms and perceived wellbeing. It is possible to determine whether a person’s health is improving or deteriorating by studying activity scores and curves.
There are many practical and useful applications for actimetry. The high sensitivity means that even falls and accidents resulting in immobility are indicated in the activity curves. Poor quality or disturbed sleep is also recorded. When monitored in real time, it means help can be lifted and a crisis can be averted.
A powerful use of actimetry is to assess the effectiveness of the care service and medications. By reviewing activity curves and information such as titration and drug delivery, it is possible to understand how recovery is affected. Practices can be refined to ensure their effectiveness. The same is possible when comparing circadian activity to care visits and practices. Similarly, activity curves can predict functional outcomes in rehabilitation and recovery. By comparing measurements between individuals with similar conditions, resources can be better managed.
An actimeter like the Vivago Care watch takes actimetry to a new practical level. In addition to monitoring circadian rhythms and providing extremely accurate activity curve data, it has a personal alarm function. This allows patients to sound an alarm when urgent help is needed. The Vivago watch is linked to a base station that integrates with on-site emergency alarms, telecare services and care service providers. This means that rhythms can be monitored in real time. Alerts are also received when patient health deteriorates, and automatic alarm calls are triggered when a fall or other serious issue is detected. This enables emergency services to respond quickly to patient needs. It saves lives where time is such an important factor.
“Objectively measured data can be shared with the multi-professional team involved in the client’s care, such as doctors, nurses and physiotherapists.
The Vivago solution helps healthcare professionals to more accurately assess the status of their clients. When the assessment of the person’s situation is based solely on their verbal description, or even on hand-written sleep or mood diaries, all the relevant information is not always conveyed. Information is subjective, easy to forget and often difficult to interpret. Adding a component that produces objective data will help the clinician better understand their patient.
Objectively measured data can be shared with the multi-professional team involved in the client’s care, such as doctors, nurses and physiotherapists. – Vivago Oy, Finland
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