Members of the organization’s existing Consumer Advisory Group (CAG) were invited to provide feedback on study procedures and the prototype device during a regular CAG meeting that was attended by the research team. The CAG comprised current or former home care recipients who met regularly to provide community perspectives on organizational and research activities. Participation was voluntary.

In phase 1, the study procedures, activity log, and prototype device were presented to CAG members in a 1-hour discussion. Researchers documented recommended changes. Consenting participants then tested the device and activity log for 1 week, followed by a home-based semistructured interview with researchers (RO or GJ) about the process and experience. Interviews were audio-recorded and transcribed verbatim. A follow-up discussion was held with the CAG, where initial findings were shared and further feedback was invited. Feasible modifications to the study procedures, device, and activity log were implemented before phase 2.

Due to its formative purpose of informing phase 2 and the small sample size, phase 1 qualitative data from interviews and notes were reviewed by RO and GJ using a pragmatic, structured, iterative process focused on identifying actionable items. Feedback and observations were identified and organized into key areas relating to the device, participant instructions, and activity log completion. Within each area, potential improvements, barriers, enablers, and user experiences were identified. Findings were discussed with the research team and subsequently refined through feedback from the CAG before being finalized.

A total of 23 participants (15 women; mean age 79.4 y, SD 6.7 y) were recruited to phase 2, of whom 7 were classified as lonely. Recruitment through the aged care organization yielded 6 participants over 6 months. Reported barriers identified by nurses included ineligibility due to cognitive impairment or mental health conditions, limited English proficiency, or lack of interest in participation. Additional community recruitment improved enrollment, but the planned matched sampling by loneliness, age, and gender was not achieved. These challenges highlight feasibility constraints in recruiting older adults for wearable technology-based research, particularly where eligibility criteria, perceived burden, and contextual factors, such as COVID-19, intersect.

Participant characteristics are presented in Table 1. The final sample comprised individuals with relatively high education levels, living in predominantly socioeconomically advantaged areas, yet a substantial proportion relied on government support. Participants also reported a range of functional limitations, including problems with mobility and usual activities, alongside common sensory challenges such as vision and hearing impairments.

Because insufficient synchronized data were generated, planned inferential analyses were not undertaken. Descriptive findings are, therefore, reported as feasibility outcomes and indicate high variability in device wear, low completion of repeated loneliness measures, and insufficient synchronized data to support the exploration of the relationship between conversation time and loneliness.

A primary feasibility question was whether participants generated sufficient synchronized device-derived conversation data and self-reported loneliness data to support exploratory analysis. Table 2 below provides a summary of feasibility outcomes.

Participants broadly understood and supported the concept of addressing loneliness but questioned whether the quantity of conversations is a meaningful indicator of loneliness. For some, “the number and amount of conversations I have really isn’t something that makes a difference to me” (P2_10). Others stated that they preferred to listen rather than talk. Furthermore, it was not the quantity of conversations, but rather the quality that was relevant, as described in the following quote:

When considering triggering contact with a nominated person, again, it was important to participants that this be tailored to the individual. Most thought that face-to-face contact would be most ideal, but others shared that a phone call or a text message would also be feasible or even preferred.

The relationship with the nominated person was seen as critical, with participants articulating that it needed to be the right person, someone they knew, could engage with, and had a real connection with. The majority stated that it should not be an unknown volunteer, but rather a personal friend, stemming from a desire for mutual reciprocity rather than obligation.

Interestingly, despite the acknowledged need for a way to identify when someone was experiencing loneliness to enable timely interventions, many participants intimated similar sentiments, “That might work for some, not all, But I don’t think I have the need for it,” (P2_4) often because they felt they already had the level of interaction that they needed. Participants did identify that the device might be a potential safety net for people who do not get as much social contact, are estranged from family members, or are lonely. Some of these participants stated that they would engage as the nominated person on the other end of an alert, supporting someone who wants conversation.

These findings highlight a fundamental conceptual limitation, in that conversation quantity may not function as a standalone proxy for loneliness and may require integration with more nuanced, relational measures.

The physical design of the device was not deemed acceptable and was a major barrier to sustained use for all 23 participants. Overall, the prototype was considered too large, heavy, and clunky, with sharp edges; as P2_1 noted, “It’s like wearing a brick around your neck,” similarly described as “annoying,” “a cumbersome thing,” “awkward to wear,” and something that “got in the way.”

Some participants stopped wearing the device entirely (n=2), while others selectively removed it during activities (n=14). The design meant that participants chose not to wear the device when they knew they were not going to engage in any conversations, as it was “a pain in the you-know-what to have to wear it” (P2_15). Participants also reported concerns related to visibility (eg, flashing light), aesthetics and stigma, and interference with daily activities, as described by the participant below.

The use of a lanyard to compensate for clip failure further reduced comfort and usability.

Some participants were particularly concerned about the lack of consideration given to design and strongly recommended that, in the future, biomedical engineers consider design before testing any device with participants.

For those with other medical assistance devices (eg, medical alert, smart devices, or falls pendants), comparisons were made with the less obtrusive design of those other devices and their better integration into participants’ lifestyle.

The participants were unanimous that device design significantly affected engagement, leading to reduced wear time and directly impacting data completeness. Usability and aesthetics emerged as critical determinants of feasibility.

Participants reported multiple acceptability issues related to device functionality, that is, how well the device worked and how users could interact with it. Although the device was made specifically for use by older community members, some components were not practical for older adults with reduced dexterity or people with less acute vision.

The main issues were the small and fiddly charging port and the on/off switch. Both were crucial for the device to be used successfully; however, many participants had difficulty with the prototype configuration.

There were numerous malfunctions with the device, particularly with the light that indicated whether it was working or charging. As a result, some participants wore the device but were concerned or unaware that it was not collecting data correctly, were disconcerted when the lights went off following charging, or had to switch devices partway through the trial. Device failures required replacements during the study in some cases, further disrupting data collection.

Despite the troubleshooting and extensive support from the research team, participants were also concerned about using the device “correctly.”

Functional limitations reduced trust in the device and increased participant burden, contributing to inconsistent use and incomplete data.

As technologies designed to promote well-being in older adults become more common, wearable devices are expected to be functional, appealing, and integrated into everyday life [25]. Device design affected recruitment and engagement in this study, consistent with previous research [26]. Participants consistently described the prototype as too large, heavy, and visually conspicuous, and many limited their use because it was uncomfortable, intrusive, or incompatible with daily activities. These issues directly affected feasibility by reducing wear time, increasing selective nonuse, and ultimately limiting analyzable data.

The findings reinforce prior work, indicating that devices for older adults must be comfortable, discreet, and easy to use to support sustained engagement [25,26]. As Moore et al [26] observed, “Any device should serve its purpose, and the primary function of the device should be reliable and easy to use; cause minimal disruption in users’ lives, be aesthetically pleasing, and should not draw attention to the user or single them out as a patient.” The present findings suggest that these expectations apply even during feasibility testing. A technically promising prototype may fail before the underlying concept can be evaluated if it is uncomfortable, unattractive, or difficult to operate.

These findings also have implications for co-design. Although engineers, clinical researchers, and older adults contributed to the later stages of device and protocol development, older adults were not involved in initial ideation and design [2]. Persistent usability concerns suggest that participation at later stages was insufficient. Human-centered design approaches emphasize involving end users early and iteratively so assumptions about aesthetics, wearability, and usability can be challenged before major development decisions are made [2,26,39,40]. In this study, consumer feedback improved aspects of the protocol and device, but resource limitations prevented substantive redesign. Earlier and more meaningful involvement of older adults as design partners in both ideation and design [2] may increase both acceptability and the likelihood of achieving study aims while reducing unintended ageism in technology development [5,26].

A second major finding relates to the measurement architecture required to test the study concept. The study was not undermined by device malfunction or an isolated adherence issue but by the interaction between continuous device-generated data, categorical activity-log data, and participant interpretation of what needed to be recorded.

The device produced continuous, time-stamped speech data, whereas the activity log required participants to summarize activities and loneliness in 6-hour blocks. Although device data were later grouped into these periods, temporal precision was reduced and interpretation was constrained. High rates of missing data, particularly in evening and overnight periods, further limited synchronization. Researchers were also unable to access device data in real time, meaning that device problems and insufficient data capture were not identified until the study had concluded.

Participant behavior added further complexity. Many participants interpreted the device as measuring conversation only and therefore did not wear it during periods when they did not expect to speak. However, both conversation and silence were important to evaluating the study concept. Researchers were also cautious in enforcing high levels of device wear because of concern that participants would cease wearing it altogether. These findings highlight a key challenge in passive sensing research: participants engage with devices according to their own understanding of what is important. Future studies will require clearer communication about the importance of capturing both event and nonevent time, alongside systems that enable real-time monitoring and correction of data capture problems. More broadly, feasibility depends not only on technical capability but also on alignment between the technology, protocol, and participant understanding.

The qualitative findings raise important conceptual implications. While the device was designed to quantify time spent in conversation, participants frequently questioned whether conversational quantity was meaningful in itself. Instead, they emphasized the quality, meaning, and personal relevance of interactions. As one participant observed, a brief interaction with the “right” person could be far more significant than an extended casual conversation. This challenges the premise that conversation time alone can function as a sufficient indicator of loneliness.

Identifying appropriate technological markers of loneliness remains challenging [41]. Loneliness is subjective [42] and multidimensional and is influenced by factors at the individual, interpersonal, community, and societal levels [43]. Quantitative findings also suggest that measurement strategy and participant burden strongly influence feasibility. The single-item loneliness measure may have lacked sensitivity to capture the dynamic nature of loneliness in this context and may have been influenced by participant interpretation or reporting bias related to stigma [44]. Our findings suggest that conversation quantity may be one component within a broader multidimensional model rather than a standalone indicator. This aligns with literature emphasizing the cognitive, relational, and situational complexity of loneliness [42,43,45].

The findings also highlight the potential role of stigma. Participants often viewed the device as something that might benefit “other people” rather than themselves. In parallel, the visible and somewhat clinical appearance of the prototype may have amplified concerns associated with wearing a health-related device in public [46,47]. Future technology-enabled approaches to loneliness will therefore need to consider not only measurement validity but also identity, dignity, and the social meanings attached to both loneliness and wearable devices.

A key strength of this study was demonstrating that the concept for a device such as the CaT Pin cannot be separated from its usability and acceptability. To address this novel research question, we adopted a pragmatic mixed methods approach, triangulating quantitative and qualitative findings to provide a comprehensive assessment of feasibility, including device performance, participant experience, and data capture processes. A further strength was the inclusion of older adults in prototype testing and refinement, ensuring end-user perspectives informed evaluation of both the device and study procedures.

This study has several limitations, grouped into device-related, procedural, and conceptual domains. Recruitment was a significant challenge. Although 30 participants were planned (15 lonely and 15 not lonely), only 23 were recruited (of whom 7 were lonely). Consequently, the intended matched cohort design could not be achieved. The final sample was relatively small, unmatched, and predominantly from socioeconomically advantaged areas, limiting the broader generalizability of the findings. These feasibility barriers may be even more pronounced in socioeconomically disadvantaged or less technologically engaged populations. However, the primary purpose of the study was to identify feasibility barriers affecting implementation and measurement rather than to estimate effects or test associations.

Limited project funding constrained device development and refinement. The prototype’s size, weight, and functional instability reduced sustained wear and directly contributed to incomplete data capture despite iterative refinement. These issues, particularly the device’s weight and bulk, influenced both the willingness to wear the device and the consistency of use, contributing to the limited amount of usable quantitative data captured.

Procedural limitations included recruitment difficulties, variable adherence to the study procedures, and reliance on self-reported activity logs, which were affected by missing data and participant interpretation. The challenges in synchronizing continuous device-derived data with participant-reported activity logs also highlight limitations inherent in combining passive sensing technologies with self-reported measures. Despite assurances that conversational content was not accessible, some potential participants expressed concerns regarding privacy and possible “eavesdropping,” consistent with previous research on wearable technologies [46,47]. Concerns about data breaches and scams may also have reduced willingness to participate.

The project commenced while the impacts of the COVID-19 pandemic were still being experienced, and concerns about virus exposure and social reengagement may have further affected recruitment. In addition, the lack of real-time access to device data meant that missingness, malfunction, and misunderstanding of study requirements could not be identified and addressed during the trial and were only fully recognized after data collection had ended.

A conceptual limitation was the assumption that time spent in conversation could function as an indicator of loneliness. Participant accounts suggested that the quality and meaning of interaction were more relevant to loneliness than conversational quantity.

Taken together, these limitations suggest that the inability to explore the original concept reflects not only practical feasibility barriers but also possible limitations in the underlying conceptual model. This is an important finding, indicating that future technological approaches to loneliness detection may need to move beyond single passive behavioral indicators and engage more directly with the subjective and multidimensional nature of loneliness.