Article Archive

September/October 2009

New Perspectives on Elders’ Sleep
By Majd Alwan, PhD, and David C. Mack, PhD
Aging Well
Vol. 2 No. 4 P. 18

Technology provides innovative methods to identify and treat sleep disorders in older adults.

For thousands of years, sleep was widely regarded as a passive process, with dreams considered only short interruptions to this state of reduced awareness and sensitivity. It wasn’t until well into the 20th century that key discoveries about the neurological and physiological activity associated with sleep debunked this long-held perspective. Once it was realized that sleep was not passive, it opened a new era in sleep research.

Sleep is now correctly characterized as a dynamic state controlled by specific and complex mechanisms. In his 1989 book Sleep, J. Allan Hobson, MD, rightly emphasized the impact of this progress by stating that “more has been learned about sleep in the past 60 years than in the preceding 6,000.” Despite the advancements made in sleep research, there is still no clear consensus about why sleep is necessary. Some postulate that sleep allows the body time to repair itself on the cellular level, while others focus on what happens when people are sleep deprived. Sleep loss affects cognitive function, mood, hormone balance, and immune system function and could hold clues to why we require that downtime each day.

Aging and Sleep
Slow wave (deep) sleep decreases as individuals age (around 2% per decade) from early adulthood to about the age of 60. Individuals aged 60 and older show decreases in sleep efficiency (actual sleep period divided by time in bed) and an advancement of their circadian rhythms (i.e., earlier bed times and earlier wake times). Inconsistencies of environmental and behavioral cues contribute to the change in circadian patterns, while increasing health problems generally contribute to sleep disruption.

According to the National Sleep Foundation’s 2003 Sleep in America Poll, which focused on the sleep of older adults, nearly one half (48%) frequently had at least one symptom of insomnia. The main cause of insomnia is related to waking up in the middle of the night and not being able to return to sleep. Part of this results from the nearly two thirds of older adults (65%) who report having to get up to go to the bathroom at least a few nights per week. This fragmentation of sleep leads to decreases in sleep quality and increases in daytime sleepiness. Some of the rise in the prevalence of these conditions can be attributed to independent factors associated with aging, including bereavement of a loved one who has passed away and mental health deterioration, but it is still clearly an important area of interest.

Sleep is necessary to maintain physical, mental, and emotional health, and the changes that occur in older adults over time with regard to their sleep can affect how well rested they are each day on each of these levels. There is a need to gain a better understanding of older adults’ sleep problems and any role they may play in cognitive decline. This could be crucial to unlocking secrets related to dementia and Alzheimer’s disease.

Furthermore, there is a need to establish a baseline of the changes in sleep that occur with aging, so treatments can be properly targeted to elders who most need them. Longitudinal studies, especially those centered on circadian patterns, are necessary to accomplish these goals, and new noninvasive technology acceptable for use in the home environment should be implemented to enable large-scale, long-term studies to be conducted in a natural setting. This objective data could offer a clear look at the sleep patterns and habits of older adults, potentially providing answers to some of the questions about cognitive decline and changes in sleep behavior.

Importance of Sleep
In the 2005 Sleep in America Poll, there appeared to be a decreasing trend in the amount of sleep Americans are getting. Only 26% of adults get at least 8 hours of sleep per night during the week (down from 38% in 2001), and 49% get that amount on the weekends (down from 61% in 2001). Additionally, 45% of Americans are voluntarily willing to reduce their amount of sleep, with 68% suffering from decreased concentration and 66% experiencing difficulty handling stress as a result of sleep deprivation.

While people who voluntarily lose sleep can often resolve this problem without treatment, about 50 million to 70 million Americans (between 15% and 25%) are suffering from sleep-related problems or clinical sleep disorders that disrupt sleep and create a detrimental effect on their health. On a broader level, about 75% of Americans indicated that they have at least one symptom of a sleep problem a few nights per week (up from 69% in 2001). However, the same survey indicates that 76% of Americans do not believe they have a sleep problem, and only 45% would report it to their doctors if they felt they had sleep issues. Untreated sleep disorders lead to losses in productivity totaling around $46 billion annually in America, and health problems, including a higher risk of stroke or even death, with an estimated 38,000 deaths annually attributed to complications from a particular disorder called sleep apnea.

Numerous conditions disturb the normal sleep cycle. For example, sleep apnea, more broadly labeled sleep-disordered breathing, is prevalent in the American population, affecting at least 12 million Americans. The most prevalent form of sleep-disordered breathing is obstructive sleep apnea. Many sufferers do not undergo examination because of the cumbersome nature of both the diagnosis and treatment, leaving their conditions undiagnosed. This is potentially dangerous since undiagnosed obstructive sleep apnea could lead to an increased risk of heart attack, stroke, diabetes, or having an accident caused by excessive daytime sleepiness.

Obstructive sleep apnea is quantified by counting events termed apneas (stoppages of breathing during sleep for at least 10 seconds) and hypopneas (reduced breathing below a threshold for at least 10 seconds) that may occur only a few times per hour in normal subjects or beyond 15 times per hour. Sleep-disordered breathing severity is reported using the apnea-hypopnea index, which calculates the number of those events per hour of sleep. According to the American Academy of Sleep Medicine, patients are said to have obstructive sleep apnea syndrome if they have an apnea-hypopnea index greater than 5 and have excessive daytime sleepiness not associated with another cause or two or more other symptoms of disturbed sleep without another cause.

The standard therapy to treat sleep-disordered breathing uses constant positive airway pressure devices generally composed of a mask and an air pressure system that forces the airways to stay open during sleep. These tend to be cumbersome and expensive yet may be the only way an individual with severe obstructive sleep apnea syndrome may be able to consistently sleep well. The Centers for Medicare & Medicaid Services criteria for reimbursement requires the patient to have an apnea-hypopnea index of greater than 15, or an apnea-hypopnea index of greater than 5 with one or more of the following conditions: hypertension, stroke, sleepiness, ischemic heart disease, insomnia, or mood disorders.

Sleep Assessment Technologies
Established as the clinical standard for sleep analysis, conventional overnight polysomnography records many physiological characteristics to provide a comprehensive analysis of sleep. Developed in the 1950s and expanded in the 1960s to include cardiac and respiration monitoring with the discovery of sleep apnea, the goal of polysomnography is to provide comprehensive monitoring of many physiological parameters, quantification of sleep patterns and stages, and diagnosis of noncircadian sleep disorders, such as sleep-disordered breathing or periodic leg movement. Highly detailed and thorough in its analysis of sleep, it usually involves monitoring brain wave patterns, eye movements, muscle activities, cardiac function, and blood oxygen saturation along with respiratory airflow and effort over a single night, with a trained technician performing the equipment setup, observation, and data scoring.

When someone needs to be observed for multiple nights to address circadian-related problems, a device known as an actigraph is used as the standard analysis tool. Employing an accelerometer, actigraphs are wristwatch-sized devices that output different numeric values with respect to changes in a person’s limb orientation and the speed with which the change occurs. These values are sampled multiple times per second, aggregated over a set epoch (usually one minute), and stored locally on the device for later retrieval. The data aggregation allows the actigraphs to record movements for many days in a row, providing longitudinal data about circadian rhythms and the individual’s activity patterns. However, the American Academy of Sleep Medicine does not recommend this technology for use in diagnosing specific sleep disorders but sees it as useful for providing objective data for different sleep patterns and characteristics in addition to subjective sleep diaries.

Passive Sleep Monitoring
In its most basic principle, ballistocardiography is a recording of minute movements associated with cardiac contraction and relaxation, as well as the movement of blood throughout the vasculature. Most of the forces recorded by ballistocardiography are a result of the blood being pumped out of the heart and around the aortic arch. Under normal conditions, the displacement caused by the reaction force of the body is very small and often unnoticeable unless measured with sensitive equipment while the individual is isolated from the ground.

One of the first modern technologies to employ this technique is the static charge sensitive bed. It uses two thin metal sheets that vary the electrical charge between them based on electrostatic buildup from an individual’s movements in bed. The growing recognition of adverse effects from poor sleep and sleep disorders has prompted more interest in developing physiologic monitoring techniques that can provide longitudinal monitoring of individuals’ health conditions. This is evident from recent studies that attempt to monitor vital signs and/or sleep with alternative methods, many of which involve pressure, vibration, or fiber optic sensors. One example of this kind of low-cost, passive sleep monitoring technology is called the Non-Invasive Analysis of Physiological Signals system.

Researchers from the Medical Automation Research Center at the University of Virginia developed the ballistocardiography-based monitoring system to measure heart rate, breathing rate, and musculoskeletal movement. The system relies on its highly sensitive pressure transducer pneumatically connected to its resilient force-coupling pad, which can be installed on top of the mattress of any standard bed. An individual simply lies down on the bed to interact with the system. The pad is 2 inches wide, so there is the option to use multiple pads to acquire data from different parts of the body. The system is sensitive enough to gather data even when sheets and blankets are applied over the pad. Once the signal is acquired from the sensor, it employs a combination of analog signal processing and automated postprocessing algorithms to generate usable data.

Even before undergoing more rigorous testing, the Non-Invasive Analysis of Physiological Signals System proved useful as a qualitative sleep assessment tool in an assisted living environment. During two clinical trials involving 60 subjects conducted at the University of Virginia, the system demonstrated strong agreement with standard measurement techniques of heart rate (electrocardiogram) and breathing rate (inductance plethysmography). The performance of the system was maintained over a wide range of heart rates and subject demographics. Additionally, the system had a high correspondence with actigraphy movement, proving qualitatively to be more sensitive to subtle movements. By using these three basic parameters of heart rate, breathing rate, and movement as a foundation, algorithms were developed to analyze sleep architecture (quantification of the various stages of sleep) and sleep apnea severity. It performed as well as actigraphy in distinguishing periods of wakefulness and sleep throughout the night when both techniques were compared with polysomnography. Interestingly, the system outperformed actigraphy in distinguishing sleep onset. In addition, it was able to objectively report when the individual was in or out of bed.

The system also performed well for classifying the severity of sleep apnea and has the potential to be used as a screening tool for sleep apnea classification. An additional algorithm, developed during the clinical trials, aims to classify people into three categories with respect to needs for sleep apnea treatment: polysomnography no treatment required, diagnostic polysomnography recommended, and treatment necessary. The system correctly classified 29 of 30 subjects using these three categories and recommended that only 12 of 30 go through diagnostic polysomnography. Though more studies are necessary to fully substantiate these conclusions, the system appears to be a promising tool for use in longitudinal, unattended home sleep studies.

Applications for the Non-Invasive Analysis of Physiological Signals system are numerous, as it has the versatility to be a low-cost, long-term monitoring apparatus for environments such as assisted living and skilled nursing facilities, as well as the home. It has the ability to provide objective data to nurses to assist them in making adjustments to their patients’ care plans to improve elders’ quality of life. It also allows them to detect health conditions early on when the system is used with daytime activity monitoring equipment. Clinically, the system has a potential application as a detailed sleep analysis tool that can provide a more comfortable, nonrestrictive approach to sleep studies for the screening and detection of sleep apnea. It can also be used as a tool to evaluate the effectiveness of medications or various treatments.

New technologies and approaches for the measurement, assessment, and quantification of physiologic variables during sleep are needed. Evolving methods such as the Non-Invasive Analysis of Physiological Signals System have shown promise providing the necessary quantitative accuracy and are likely to gain broader acceptance and wider applications to different settings, including the home and older adult care settings. Additional information can be found in the Sleep Assessment Technologies chapter of Eldercare Technology for Clinical Practitioners.

— Majd Alwan, PhD, is director of the Center for Aging Services Technologies at the American Association of Homes and Services for the Aging in Washington, DC.

— David C. Mack, PhD, is the director of research and development at WellAWARE Systems in Charlottesville, VA.