## 2 Literature Review
### Review of the Literature
#### 2.2.1 The Internet of Things and Aging in Place  
The introduction to Section 1 provided a high-level explanation of the Internet of Things (IoT). This section provides more details and context into the IoT as it relates to the technologies for older adults to age in their homes longer, increase safety, security, and maintain quality of life standards. The IoT is the concept that virtual and physical objects (e.g., refrigerators, stoves, and carbon monoxide monitors) have unique identifiers, are connected to the Internet, and communicate with each other [66, 67, 26]. In the context of aging in place, a human could also be connected to, and automatically communicate with, objects through a wearable or implanted medical device [68]. Heartbeat, glucose, respiration, or temperature monitors have been used to continuously monitor patient vitals and send that data to a cloud environment where a health practitioner could retrieve and analyze it [69, 70, 71]. In addition to objects and humans, the IoT connects animals, plants, buildings, automobiles, and scooters [72]. This ubiquitous communication enabled new healthcare solutions for aging adults, such as IoT-based rehabilitation, telemedicine, and activity tracking [73, 74]. Sensors, actuators, networking, wireless, computers, and software were combined to collect, send, receive, process, and analyze data. These technologies combined with preventative healthcare were viewed as the optimal means to ensure that older adults remained healthy and active, supporting their independence [8, 17]. The ratio of adults above the age of 60 to working age adults in the U.S. was increasing significantly, and organizations expect the total number of older adults to exceed the number of persons under the age of 18 by 2035 [75]. Researchers studying life expectancy across 35 countries reported that an increase in older adults would be a global reality [76, 77]. If these predictions are correct, older adults will comprise 30% of the population and will likely continue to increase due to a consistent decline in population growth [75]. As people age, their vision, hearing, cognitive, and physical abilities may decline, which can contribute to unsafe conditions. These include wandering outside the home at night, forgetting to turn off the stove, falling in the bathroom, or tripping over an object. The rapid growth of the aging population, their naturally declining health, and the increasing demand on healthcare providers spurred research into technologies that could be used by older adults to maintain independence, health, safety, and quality of life [73, 74, 77, 78]. Researchers combined IoT technologies in different ways for older adults to monitor their home environments, provide safety alerts, communicate over the Internet, and overcome disabilities [21, 74, 78, 79]. Virtual assistants such as Alexa, Amazon Echo, and Google Home enabled vision impaired persons to obtain news, set reminders, and communicate with others [80]. The academic literature on IoT solutions to age in place longer focused heavily on technologies, frameworks, and experiments driven by industry requirements (e.g., healthcare, or technical developers) rather than the needs of the older adults [70, 71, 74, 81]. Several themes emerged from synthesizing the academic literature, which correlated some of the constructs of the UTAUT. These included effort expectancy, behavioral intention to use, performance expectancy, facilitating conditions, habit, and price value. Many researchers did not demonstrate an understanding of older adults' characteristics and the barriers to their acceptance of technology. Older adults had less experience with and confidence in using newer technologies [82, 83, 84]. They preferred to continue using old, outdated technologies instead of adopting the newer [15, 43, 63, 85]. Most of the IoT solutions proposed or experimented with required newer technologies and user familiarity with them [81, 83, 86, 87]. In some cases, the older adults were physically unable to manipulate the technology.