Sleep

Insufficient sleep is common: almost 30% of adults in the United States report sleeping six or fewer hours per day. Inadequate sleep can cause symptoms of drowsiness, drowsy driving, fatigue, irritability, incoordination, and attention deficits; and is associated with heart disease, obesity, and increased mortality.

The National Sleep Foundation recommends that adults aged 18 to 64 years sleep seven to nine hours per night [1]. For those 65 years of age and older, seven to eight hours is recommended. Infants, children, and teenagers require more sleep than adults.

Maiaa, et al found that 3.6% of people in the general population reported incidences of drowsy driving (defined as nodding off or falling asleep, even just for a brief moment) during the past 30 days. People who slept less than 6 hours per night were 1.9-2.0 times more likely to report drowsy driving than 7 hour sleepers, and people who slept less than 5 hrs were 3.6-3.8 more likely [2].

A frequent sleep disorder is sleep apnea (interrupted breathing), which affects an estimated 22 million Americans. People with sleep apnea may snore and gasp for air throughout the night, causing chronic sleepiness and increasing their risk of heart disease, hypertension, Type 2 diabetes, depression, and erectile dysfunction. Sleep apnea has been reported to be the single most important preventable medical cause of excessive daytime sleepiness and driving accidents.

The most common type of sleep apnea is known as obstructive sleep apnea. This occurs when the upper airway collapses in on itself due to low muscle tone during sleep, preventing air from reaching the lungs. This can result in frequent potentially dangerous pauses in breathing while asleep termed apnea, which in turn may cause oxygen levels to drop, and blood pressure and heart rate to rise. Loud snoring and waking may occur because of the struggle to breathe.

The American Sleep Apnea Association developed a screening quiz for sleep apnea [3]:

Are you a loud or regular snorer?
Have you ever been observed to gasp or stop breathing during sleep?
Do you feel tired or groggy when you wake up? Do you wake up with a headache?
Are you often tired or fatigued during the day?
Do you fall asleep while sitting, reading, watching television or driving?
Do you often have problems concentrating or remembering things?

Furthermore, the American Sleep Apnea Association states:

If you have one or more of these symptoms, you are at higher risk for having obstructive sleep apnea. If you are also overweight, have a large neck and/or have high blood pressure the risk increases even further.

People with these symptoms should discuss them with their healthcare provider and consider sleep testing.

The quality and quantity of sleep can be assessed by questionnaire and sleep log. A more objective assessment of sleep can be obtained with actigraphy. Actigraphy records movement sensed by an accelerometer usually worn on the wrist at home. Actigraphy is well validated and correlates with formal sleep studies done in a sleep lab. It provides useful information about sleep duration and sleep quality.

Actigraphy equipment can be obtained from a sleep specialist for short term testing at home. Alternatively, people with more chronic sleep conditions can purchase a device worn on the wrist for home use called Actiwatch actigraphy system manufactured by Phillips.

In recent years multiple manufacturers have developed Consumer Sleep Technology (CST) devices that purport to assess sleep, and are available at lower cost than the Actiwatch system. However, it is important that these devices be validated for the measurment and analysis of sleep-wake periods.

The American Academy of Sleep Medicine (AASM) has released a position statement about Consumer Sleep Technology [4]:

It is the position of the AASM that CST must be FDA cleared and rigorously tested against current gold standards if it is intended to render a diagnosis and/or treatment. Given the unknown potential of CST to measure sleep or assess for sleep disorders, these tools are not substitutes for medical evaluation. However, CSTs may be utilized to enhance the patient-clinician interaction when presented in the context of an appropriate clinical evaluation.

The AASP concluded:

CST is widespread and may improve patient engagement. Benefits of CST include increased awareness of the importance of sleep and the need for evaluation and treatment of sleep disorders. CSTs may enhance the patient-provider interaction and as such, are adjuncts to clinical practice. …PGHD [patient-generated health data] derived from CST should be considered in the context of a comprehensive sleep evaluation and should not replace validated diagnostic instruments. CST delivered interventions are not substitutes for treatments that have undergone rigorous scientific investigation. Despite their limitations, CSTs may allow for meaningful conversations with patients and increase active participation in their health care.

One popular consumer sleep technology device is manufactured by Fitbit, which has been evaluated in published clinical studies. In a study by Zambotti, et al Fitbit was compared to polysomnography [PSG] in a sleep lab (the gold standard of sleep analysis) [5].

In the main group, Fitbit Charge 2™ showed 0.96 [out of 1.0] sensitivity (accuracy to detect sleep), 0.61 specificity (accuracy to detect wake), 0.81 accuracy in detecting N1+N2 sleep (“light sleep”), 0.49 accuracy in detecting N3 sleep (“deep sleep”), and 0.74 accuracy in detecting rapid-eye-movement (REM) sleep. Fitbit Charge 2™ significantly (p < 0.05) overestimated PSG TST [total sleep time] by 9 min, N1+N2 sleep by 34 min, and underestimated PSG SOL [sleep onset latency] by 4 min and N3 sleep by 24 min. PSG and Fitbit Charge 2™ outcomes did not differ for WASO [wake after sleep onset] and time spent in REM sleep. No more than two participants fell outside the Bland–Altman agreement limits for all sleep measures. Fitbit Charge 2™ correctly identified 82% of PSG-defined non-REM [rapid eye-movement]–REM sleep cycles across the night. Similar outcomes were found for the PLMS [periodic limb movement of sleep].

The article concluded:

… Fitbit Charge 2™ shows promise in detecting sleep-wake states and sleep stage composition relative to gold standard PSG, particularly in the estimation of REM sleep, but with limitations in N3 detection. Fitbit Charge 2™ accuracy and reliability need to be further investigated in different settings and in different populations in which sleep composition is known to vary in which sleep composition is known to vary (adolescents, elderly, patients with sleep disorders).

In another study, Lee et al compared Fitbit Charge HR to the Actiwatch 2 in 16 healthy young adults [6]. They found that:

The periods and acrophases [peaks] of the circadian rest-activity rhythms and the sleep start times did not differ and correlated significantly between the Fitbit Charge HR and the Actiwatch 2. The Fitbit Charge HR tended to overestimate the sleep durations compared with the Actiwatch 2. However, the sleep durations showed high correlation between the two devices for all days.

In conclusion, the findings of this study showed that the Fitbit Charge HR is a valid, reliable, and alternative device to use for sleep evaluations and circadian rest-activity rhythm measurements compared with actigraphy in healthy young adults. However, the sensitivity of the Fitbit Charge HR for accurately identifying activity was lower than actigraphy. Additional studies need to be performed on the validity of wearable activity trackers…

An alternative to wearing a watch, The SleepScore Max by ResMed is a non-contact, bedside device that uses ultra-low power radiofrequency (RF) 100 times lower than that of a standard mobile phone to detect motion, and thus does not affect user comfort while sleeping. It detects sub-millimeter movements of the chest wall and can monitor movement and respiration without direct contact with the subject. With this technology, the device can identify sleep stages including wake, light sleep, deep sleep, and REM.

The SleepScore Max was validated by an independent sleep laboratory in 38 healthy individuals in 2018. Preliminary results are published on the SleepScore website [7].

For Wake, Deep and REM sleep annotation, the performance on accuracy (correct annotation of both the occurrence and non-occurance of a certain sleep stage epoch compared to PSG) and specificity (ability to annotate the non-occurrence of a specific sleep stage epoch correctly compared to PSG) are high (all >83%). The sensitivity (ability to annotate a specific sleep stage epoch correctly compared to PSG) results are lower ranging from 55-66%.

Zaffaroni eta al [8] studied the ResMed non-contact sensing technology. They concluded:

The SleepScore Max was validated by an independent sleep laboratory in 38 healthy individuals in 2018. Preliminary results are published on the SleepScore website [7].

Non-contact sensing technology can allow quantitative measurement of sleep beyond the hospital setting, in a user-friendly and cost-effective manner. …In this study, the sleep staging performance of a novel non-contact sensing technology was compared to PSG on healthy subjects. … PSG scoring for this study compared favorably to the scientific literature. The non-contact device algorithm produced good performance compared to PSG. No statistically significant difference in total time for each sleep stage, in sleep onset or sleep efficiency was observed. Furthermore, performance of the non-contact device in detecting Wake, REM and N3 sleep stage was superior to that reported in the literature for wrist actigraphy. The non-contact sensor technology presented can provide a viable alternative to PSG in the home environment, allowing reliable monitoring of long-term sleep trends.

O’Hare et al compared radio-frequency biomotion sensors and actigraphy vesus polysomnography in 2014 [8].

The three technologies evaluated were (a) a radio-frequency based biomotion sensor operating at 5.8 GHz (SM, ResMed Sensor Technologies, Dublin, Ireland), (b) a radio-frequency-based biomotion sensor operating at 10.525 GHz (HSL-101, Omron, Kyoto, Japan), and (c) a wrist-based actigraphy sensor (Actiwatch (AW)-2, Philips Respironics, USA). The principle of operation of the two radio-frequency-based biomotion sensors is that they detect bodily movement and respiration movements by transmitting a low-power pulse of radio-frequency energy. By monitoring the echo received from the subject, the movement of the subject can be determined.

We conclude that this study shows the validity of radiofrequency-based motion sensors to provide sleep/wake measurement with a similar performance as existing actigraphy systems. It remains a topic of ongoing research whether the additional respiration information provided by these sensors can actually be used to improve the sleep/wake estimation capabilities in a statistically significant manner. Limitations of the study include the fact that the subject population represents a normal population free of sleep disordered breathing and primary insomnia, and hence these results cannot be extrapolated to those clinically important populations. Since the sleep recordings were taken in a lab system using a tethered PSG system, the “sleep opportunity” presented to the subjects will be different than in their home environments.

A novel consumer wearable device for sleep is the Beddr SleepTuner. This device is an FDA listed product that is designed to help people analyze their breathing during sleep particularly in relation to sleeping position. It is a small device that is worn on the forehead during sleep, and monitors blood oxygen levels, heart rate, and stopped breathing events in relation to body position.

This device is a [9]:

… wellness oximeter, a non-invasive overnight recording device that measures and displays functional oxygen saturation of
arterial hemoglobin (SpO2), stopped breathing events per hour, Heart Rate (HR), sleeping position and movement.
…The SleepTuner works in conjunction with an application that runs on a mobile phone.

According to the manual:

Beddr is not intended for medical use or to inform healthcare

decisions. Beddr is not intended to cure, prevent or treat a disease.

Beddr margin of error for SpO2 over a 70-100% test range was plus or minus 2.2%, which meets FDA standards.

Conclusion

Sleep deprivation is an important medical problem, which is frequent and potentially dangerous. Several wearable and noncontact devices are available to help monitor sleep at home and inform both consumers and healthcare providers about the duration and quality of sleep. However, as stated by Kosla et al [4] a device:

must be FDA cleared and rigorously tested against current gold standards if it is intended to render a diagnosis and/or treatment. Given the unknown potential of CST to measure sleep or assess for sleep disorders, these tools are not substitutes for medical evaluation.

1. https://www.sleepfoundation.org/press-release/national-sleep-foundation-recommends-new-sleep-times

2. Short and long sleep duration and risk of drowsy driving and the role of subjective sleep insufﬁciency. Maiaa Q, Grandnera MA, Findleya J, Gurubhagavatulaa I. Accident Analysis and Prevention 59(2013) 618-622.

3. http://www.sleepapnea.org/wp-content/uploads/2017/02/snore-score.pdf

4. Khosla S, Maryann C. Deak MC, Gault D, et al. Consumer Sleep Technology: An American Academy of Sleep Medicine Position Statement. J Clin Sleep Med. 2018 May 15; 14(5): 877–880.15.

5. Comparison of Wearable Activity Tracker with Actigraphy for Sleep Evaluation and Circadian Rest-Activity Rhythm Measurement in Healthy Young Adults. Hyun-Ah Lee, Heon-Jeong Lee1, Joung-Ho Moon, Taek Lee, Min-Gwan Kim, Hoh In, Chul-Hyun Cho, and Leen Kim. Psychiatry Investig 2017;14(2):179-185

6. https://www.sleepscore.com/sleepscore-max-sleep-tracker/

7. Non-Contact Estimation of Sleep Staging. Zaffaroni A, Doheny DP, Gahan L, et al. EMBEC 2017, NBC 2017: pp 77-80.

8. O’Hare E, Flannagan D, Penzel T, et al. A comparison of radio-frequency biomotion sensors and actigraphy versus polysomnography for the assessment of sleep in normal subjects. Sleep Breath 2015 19:91-98.

9. https://www.beddrsleep.com/healthcare-professionals

Disclaimer: Since healthcare is complicated and personal, you should discuss these topics with your healthcare provider before applying this information to your own health. This website does not intend to diagnose or treat any disease or medical condition. Its only purpose is to assist people to monitor their health at home under the supervision of their healthcare provider.

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