Contents I. Introduction
Falls are the leading cause of fatal and nonfatal injuries to the elderly in the modern society. According to the center for Disease Control and Prevention, one out of three adults aged 65 and over fall each year at home [1], [2]. Falls not only bring a main threat to the elderly’s health, but also account for a large part of medical cost. Most of the elderly are unable to get up by themselves after a fall, and studies have shown that the medical outcome of a fall is largely dependent on the response and rescue time [2]. The delay of medical treatment after a fall can increase the mortality risk in clinical conditions, half of those who experienced an extended period of lying on the floor died within six months after an incident [3]. In addition to physical injuries and high medical cost, falls can cause psychological damage to the elderly as well, which is termed as the fear of falling cycle by the fall researchers [3]. The fear cycle refers to the fact that after a fall, even without injury, the elderly become so afraid of falling again that they would reduce physical activities [3]. This in turn decreases their fitness, mobility and balance, and leads to decreased social interactions, reduced life satisfaction, and increased depression. This fear cycle further increases the risk of another fall. Especially for the elderly who live alone and independently, about 50% of the falls occur within their own home, so timely and automatic detection of falls has the potential to save the lives of the elderly [4].
