Recent advances in wearable sensors and portable electronics for sleep monitoring

Abstract

Despite the increasing awareness of the importance of sleep, the number of people suffering from insufficient sleep has increased every year. The gold-standard sleep assessment uses polysomnography (PSG) with various sensors to identify sleep patterns and disorders. However, due to the high cost of PSG and limited availability, many people with sleep disorders are left undiagnosed. Recent wearable sensors and electronics enable portable, continuous monitoring of sleep at home, overcoming the limitations of PSG. This report reviews the advances in wearable sensors, miniaturized electronics, and system packaging for home sleep monitoring. New devices available in the market and systems are collectively summarized based on their overall structure, form factor, materials, and sleep assessment method. It is expected that this review provides a comprehensive view of newly developed technologies and broad insights on wearable sensors and portable electronics toward advanced sleep monitoring as well as at-home sleep assessment. INTRODUCTIONWe spend almost one-third of our lifetime asleep. Sleep is an integral aspect of our life to sustain our daily activity, and the quality of sleep has a massive influence on our health, work performance, and well-being. Numerous research works have shown the association between the poor quality of sleep and many adverse effects on our health including, but not limited to, obesity, diabetes, heart diseases, hypertension, mood disorders, weakened immune system, and increased mortality risk (Buysse, 2014;Hublin et al., 2007;Patel et al., 2004;Sigurdson and Ayas, 2007). As an increasing number of people recognize sleep quality as a key component of a healthy lifestyle, research and industries related to sleep health have been actively growing. In 2019, the global sleep economy was $432 billion and was expected to grow up to $585 billion by 2024 with a compound annual growth rate (CAGR) of 6.3% (Casper, 2020). Especially when the COVID-19 outbreak has become a global pandemic, the importance of sleep is emphasized to support people's immunity and health (Gulia and Kumar, 2020;Huang and Zhao, 2020;Sher, 2020).Despite this elevated awareness of sleep health, the number of people with insufficient sleep or sleep disorders has continuously increased. In 2015, it was reported that 18% of the United States population took less than 6 h of sleep per day. Insufficient sleep caused reduced labor productivity and increased mortality, leading to an economic loss of $411 billion, which is expected to grow up to $467 billion in 2030 (Hafner et al., 2016). Furthermore, in 2015, the American Association of Sleep Medicine (AASM) reported that obstructive sleep apnea (OSA), one of the most prevalent sleep disorders, afflicted 12% of the adult population in the United States. AASM also noted that around 80% of people with OSA were undiagnosed, resulting in an economic burden of $149.6 billion due to loss in productivity and an increase in the risk of costly comorbidities (Watson, 2016). Despite their prevalen...

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