Smart wearable sensing systems mediating the digital monitoring of loneliness – A review

As mental health difficulties are of increasing concern and people are encouraged to communicate their feelings, loneliness has become a critical issue for the community, with the number of people identifying as lonely being higher than ever. Loneliness can lead to conditions ranging from simple changes in social behaviors to adverse health situations, with depression and anxiety being the dominant ones. These conditions are known to trigger a cascade of emotions then translated into alterations of physiological signals which can be detected and monitored with digital means, such as wearable sensors. The purpose of this work is to review the smart wearable sensing systems that have been used for the detection of these conditions and the recent advances in the development of these sensors. We first review the physiological signals associated with each one of the main loneliness manifestations, then we present the real-life studies performed involving participants and the use of wearable sensors and subsequently we analyze the main categories of sensors used in the studies, the technological advances and the remaining drawbacks for each one of them. Through this review we managed to examine thoroughly the current smart wearable sensing systems on digital monitoring of loneliness and to identify the most promising fields for development.