Semistructured interviews were conducted online and audio-recorded with verbal consent. Interviews typically lasted 30-60 minutes. The interview topic guide was developed based on the Capability, Opportunity, Motivation–Behavior (COM-B) [40] model (Multimedia Appendix 1). Topics included experiences of recruitment, study devices, remote contact with researchers, overall study impressions, and general feedback. Participants were explicitly asked to recall both positive and negative aspects of the study, as well as what might be improved in future research designs.

Maximal variation sampling, a form of purposive sampling, was used to nonrandomly invite participants to end-of-study interviews, based on characteristics considered relevant to acceptability of remote sleep research: age, sex, educational background, employment status, subjective sleep quality, and cohort (AD, LBD, or controls). Participants who withdrew from the study or specifically contacted the research team with study feedback were also invited to participate in an interview.

To supplement the interview data, 2 questionnaires were introduced following an ethically approved study amendment during the recruitment period: the RESTED Expectations and RESTED Experiences questionnaires (Multimedia Appendix 1). Participants joining the study or who had not yet completed their intensive week of assessments were encouraged to complete the questionnaires at the relevant time points. Participants who had completed their intensive week prior to the amendment implementation were not asked to retrospectively complete questionnaires.

Both questionnaires were developed with reference to the COM-B model and the extended Unified Theory of Acceptance and Use of Technology (UTAUT-2) model [32] and aimed to provide additional insight on participants’ perspectives prior to and during active engagement in the study. The RESTED Expectations questionnaire probed motivations, first impressions of study devices, and prior experience of technology. The RESTED Experiences questionnaire focused on the intensive week of the study, which specific tasks were easier or harder to complete, and whether research participation had influenced day-to-day life or social functioning.

Participants reported reflective motivations for study participation, perceiving it as helpful to themselves, family members, or society. However, some participants also identified that direct incentives, such as providing feedback on sleep or financial reimbursement, could help to motivate more people to participate in future studies.

Participants often cited altruistic underlying reflective motivations, recognizing that their participation would likely not directly impact themselves but might benefit others, such as family members, who might be at risk in the future:

Some participants cited more proximal reasons, specifically wanting to help the research team or clinic through research participation. One participant expressed how their appreciation for the service they receive from the health care and research team prompted study enrollment:

Other participants perceived more direct personal benefits to study participation. For instance, engaging in research activities such as cognitive testing was viewed as a form of cognitive stimulation that could help delay cognitive decline or help to manage symptoms:

Although participants were provided with personalized feedback only if they were found to have undiagnosed sleep apnea, participants also commented that study participation might indicate if they needed further investigations for their cognition or sleep. Being involved in research, and the research community, was also identified as a route to accessing potential treatments before approval.

In addition, several participants explained that the study sounded interesting or enjoyable. Research participation was generally viewed as a positive activity, helping participants to “feel useful and part of something significant.” Some participants also enjoyed having tasks to complete, suggesting that research gave them a sense of purpose or a new pastime:

Additionally, several participants noted that they took part because they had “taken part in dementia studies before” suggesting that research involvement can become habitual.

Although participants’ own motivations centered around helping themselves or others, direct incentives, such as personalized sleep or cognitive feedback or financial reimbursement to participate, were proposed as a way to facilitate recruitment to similar studies in the future:

Personalized sleep feedback was generally considered as interesting and informative but not necessarily useful or something to act on. Unless a problem was identified, few participants intended to change their sleeping habits:

Overall, motivations to participate centered around the perception of the study as helpful to themselves or others, although direct incentives (financial or nonfinancial) could also potentially motivate study participation.

Simplicity and trusting devices to work as expected was central to user experience, particularly as most study devices were unfamiliar to participants. User experience was influenced by factors such as novelty, usability, comfort, technical reliability, and privacy.

Despite most participants reporting frequent exposure to smart technology at baseline, participants were largely unfamiliar with the specific study devices or sleep wearables more generally. Participants compared unfamiliar study devices with ones they had come across before in their personal life, such as fitness trackers, creating mental anchors that helped to contextualize their purpose:

Beyond novelty, participants typically focused on practicalities, initially evaluating devices by whether they appeared simple to use and comfortable to wear.

For the most part, participants found wearable devices tolerable and minimally intrusive to their day-to-day life or sleep:

However, several improvements were suggested around ergonomic design. The silicone strap of the actigraphy watch could catch on clothing, which could interfere with activities of daily living such as getting dressed, and prolonged use also occasionally caused mild skin irritation. Participants recommended making the device smaller, lighter, and more streamlined, and possibly with a watch face, to make it more aesthetically pleasing and functional:

Similarly, while the Dreem 2 headband was largely well-tolerated, some participants identified challenges in comfort and design. For example, the small red light near the forehead sensors, which indicated that a recording was in progress, could be seen by some participants and could disrupt sleep. Positioning the headband securely enough to get a good quality trace, without being uncomfortable, was also sometimes a challenge for participants:

Simultaneous use of multiple wearable technologies could also become uncomfortable and less acceptable compared with using 1 device alone. For example, participants with sleep apnea who were using a continuous positive airway pressure mask had some difficulties with fitting the mask and the EEG headband comfortably.

Technical reliability, or how consistently the technology performed according to participants’ expectations, was also central to user experience and acceptability. Several participants reported technical glitches, often triggered by software updates. When expectations of the technology were not met, participants became frustrated, blamed or questioned their technical or cognitive abilities, and sought support and reassurance from others:

Participants also sometimes experienced confusion or frustration with interacting with different apps or websites for different tasks (eg, a mobile app for the sleep diary and a website for the cognitive tests). Developing a single platform for all remote study tasks was suggested to make the study more straightforward for participants in future studies and support better user experience.

Privacy and data security were key to engagement with many participants emphasizing the importance of nonintrusive data collection, such as the absence of cameras which are typically present during full polysomnography, or questions about sensitive topics such as dream content:

Participants often described how study tasks were not perceived as invasive or intrusive and understood that their participation was voluntary, which fostered a sense of trust and control. Protecting data security while keeping device and software interactions straightforward was also identified as a priority:

Participants often had different opinions on which components of the study were the easiest or hardest or the most or least enjoyable to complete. For example, many participants found it particularly challenging to collect saliva samples at home and reported both cognitive difficulties (eg, understanding the instructions and accurately timing sample collection) and practical difficulties (eg, fitting samples in around existing commitments and physically producing sufficient saliva):

However, other participants felt that home saliva testing was straightforward or an enjoyable part of the study, highlighting how user experience can vary substantially across participants and be influenced by ease of use and personal satisfaction:

Limited digital literacy or confidence, due to older age or less exposure to technology, was suggested as a possible influence on participants’ experiences of whether research using RMTs was acceptable or enjoyable:

Additionally, physical challenges could also complicate interactions with devices and study tasks. For instance, being able to respond quickly and accurately in the online cognitive tasks could be more challenging for people who may have conditions affecting their dexterity, such as arthritis or parkinsonism, introducing confounding factors. Beyond variations in preferences and perceived ease of use across participants, an individual’s experience was also not necessarily static or in line with their first impressions.

Perceptions of the study and individual tasks evolved over time. Being able to integrate study tasks conveniently into existing routines or commitments facilitated engagement and reduced perceptions of burden, while time-restricted tasks were a barrier. Prolonged engagement in research encouraged participants to adapt and find strategies which supported their engagement in study tasks, but repetition of challenging tasks was also linked to disengagement and study fatigue.

Being able to integrate study tasks within existing routines or commitments facilitated participant engagement and adherence. At the outset, some participants were concerned that study participation might be burdensome or disruptive to their daily lives:

Being able to develop habits or routines to complete their study tasks around their usual activities helped to reduce participant burden. To minimize burden, some participants planned out the day and prepared ahead of time by placing equipment or devices required for study tasks in plain sight:

Smartphones and digital tablets, compared with pen and paper assessments or personal computers, enabled greater flexibility around when and where study tasks could be completed, such as at home or at work. Passive data collection enabled by the actigraphy watch also supported participants to continue with their usual activities. In contrast, tasks that were requested at a specific time of day were more challenging to incorporate into routines and around existing commitments, such as trying to fit in cognitive tests before going to work:

Participants generally accepted the inconvenience of time-limited tasks which occurred infrequently (eg, once or twice during the study period); however, time-specific tasks that were repeated more frequently were less acceptable. When unavailable during the designated time, some participants felt stressed or skipped the tasks altogether, suggesting that flexibility in timing could influence adherence as well as study burden.

Participants’ attitudes toward the study tasks often changed over the course of the study. With time and experience, participants became more confident and were able to complete various tasks at differing time intervals without too much difficulty:

Throughout the study, participants often took initiative to make it easier to complete study tasks or improve their performance, suggesting that repeated exposure to the same tasks created a learning effect:

Gamification also appeared to help participants to stay engaged in repeated cognitive tasks, as some participants competed to improve their own previous score. In line with their reported motivations (theme 1), some participants self-reported benefits of regular cognitive testing such as boosted self-esteem, improved subjective cognitive functioning, and enjoyment, which may have supported prolonged engagement:

However, repeating the same study tasks over time could also lead to fatigue and negative affect. Cognitive tasks could highlight participants’ cognitive concerns, meaning they became more frustrated, anxious, or disheartened with greater exposure to the tasks:

Tasks that became progressively difficult appeared to prompt disengagement, even in participants who were initially enthusiastic about the tasks. Feeling demotivated may have meant that participants started to put in less effort or performed worse over time, which could impact the validity of high-frequency remote cognitive assessments:

While participants understood the rationale behind repeating the same series of cognitive tasks to enable comparison over time, the lack of variety meant that some participants transitioned from finding the study tasks engaging and enjoyable to tedious:

While repeated exposure to the same tasks could therefore create opportunities for learning and adaptation and participants understood why tasks were repeated, too much repetition of tasks, particularly cognitive tasks, may become a barrier to continued study participation or acceptability.

Participants were motivated to complete tasks as they had been instructed to and, for the most part, attempted to adhere to instructions on how and when to complete study tasks to the best of their ability. Perceptions of suboptimal performance on a task could contribute to negative affect including guilt, frustration, and anxiety. Social support helped to provide reassurance (theme 5).

Participants took considerable efforts to complete the study tasks as instructed. When things went wrong or were difficult, some participants experienced negative affect including feeling guilty, embarrassed, or that they had failed in some way:

Participants also found it more challenging to engage in tasks they subjectively felt they were not performing well on, including the cognitive tasks:

Being unable to meet study requirements due to conflicting commitments was also stressful for participants, who wanted to follow the study protocol as closely as possible:

Some participants found creative solutions to continue with study tasks when experiencing discomfort or when they had concerns around data quality. For example, participants reported using wires, bandages, caps, and gloves over the pulse oximeter or EEG headband to keep them in place, demonstrating how participants attempted to address concerns independently and through experience or trial and error, sometimes without consulting the research team:

However, support was often sought from the research team and relatives and is explored more in theme 5.

Participants with MCI or dementia were often concerned, particularly at the start of the study, whether their cognitive impairment and particularly their memory might impact participation. However, most participants remembered to complete tasks [33], either independently or following reminders sent by the research team:

Having printed instructions reassured participants, allowed them to problem-solve whenever they needed it, and reduced reliance on memory. In contrast, on-screen instructions at the start of each set of the unsupervised cognitive tasks, which disappeared during the task, were less well-received. Not being able to remember the instructions when engaging in a remote cognitive task could affect task performance (eg, clicking in the wrong place during the choice reaction time task) and trigger disengagement:

Verbal and written instructions could also be better complemented by visual or practical demonstrations. Participants were talked through and shown how to use the study kit at the start and were offered a call with a researcher before the intensive week. However, opportunities to physically practice tasks in the presence of the research team were recommended to build confidence in novel tasks:

Participants felt that recording sleep at home was more comfortable and that RMTs could provide a more accurate representation of their usual sleep than sleeping in a hospital or sleep laboratory:

However, concerns about devices working as intended and accurately recording sleep data were prevalent, particularly where participants had subjective sleep disturbance. One participant shared that they were skeptical about whether the devices could reliably track their sleep patterns because of nighttime movements:

Participants found it difficult to accurately self-report sleep metrics for their sleep diary and were aware that their responses might not align with the RMTs. Participants often used external cues, such as what television program had been on when they went to bed and what their partner thought, and internal cues, such as how rested and awake they felt, to help them estimate nighttime sleep duration, quality, and awakenings. Trying to complete a sleep diary was challenging due to issues with memory recall and being able to estimate the duration of time spent awake during the night:

Observer effects were also identified as a possible confound to accurately measuring sleep. For example, wearables that are uncomfortable could be a physical impediment to sleep (theme 2), while asking participants to reflect daily on their sleep could create greater self-awareness or anxiety around sleep:

Participants had varying support needs, preferences, and expectations from both the research team and the relatives who provided informal study support. Support generally fell into categories: technical support (eg, to set up mobile apps, enter data, and join video calls) and cognitive and emotional support (eg, reminders on how to complete study tasks and motivation). Face-to-face contact and responsive communication with the research team were valued highly and supported continued engagement in the study.

Someone at home, typically a partner or a relative, provided technical study support for many participants, including some controls with no cognitive impairment. The amount of support needed or provided varied substantially from support with initial setup and familiarization with novel apps to essential daily support (eg, completing digital sleep diaries):

Participants also routinely contacted the research team for technical support as needed and to report issues. Confirming successful data transfer and data quality was reassuring and provided a sense of security and connection back to the research team. Participants reflected specifically on the speed and reliability of communication with the research team, and how email communication had an additional benefit of providing a record of the conversation for participants to look back on if they encountered the problem again:

Partners and relatives also often helped with cognitive support through reminding participants to complete tasks and helped to answer the subjective questions on sleep, such as what time they woke up or went to bed:

However, several participants, including those with MCI and dementia, did not have any support at home or chose to engage in the study completely independently and had no or few issues:

Furthermore, requiring a study partner as part of the eligibility criteria was identified as a barrier to research participation. One participant with MCI shared how they had been ineligible for previous dementia research because they did not have someone available to act as a study partner and had wanted to be able to take part independently:

While most contact with the research team occurred remotely via email or video calls, in-person interactions at the clinic or at participants’ homes (eg, at baseline or midway through the study to collect study equipment or review how to complete study tasks) were expected, valued, and helped participants to feel more included in the research study:

Face-to-face interactions and developing rapport helped with confidence and mitigated against study fatigue or disengagement:

Overall, interactions with others were an important facilitator offering both practical and social support during study participation, while study partner requirements were a barrier.

Participants generally perceived good sleep as important for overall and cognitive health but were often unsure how to achieve it. Subjective sleep quality was associated with factors such as snoring, dreaming, sleep duration, and nighttime awakenings.

Total sleep duration, or getting “enough” sleep, was recognized as a key component of sleep quality by participants. Having approximately 8 hours of sleep was recognized as the target for adults, but this was not always considered to be achievable or common:

Daytime napping was also raised as an important component of sleep among older adults. Some participants used napping as a strategy to manage energy levels throughout the day or avoid going to bed early, whereas others were concerned about the health consequences of taking daytime naps and would actively avoid napping despite daytime sleepiness:

Snoring was also a concern regarding sleep disturbance. Snoring affected not only individuals but also their partners, sometimes leading to disrupted sleep, frustration, or changes in sleeping arrangements, highlighting the social as well as personal impact of sleep disturbances:

Vivid dreams were also discussed as a factor affecting sleep quality:

Overall, participants shared a range of components that could shape their perception of a good night’s sleep, extending from meeting recommendations and comparing to how others sleep to its impact on daily and social functioning.

Many participants shared how they felt both sleep and research investigating how sleep might impact health, cognition, and dementia were important:

Some participants noted that they typically felt worse and experienced worse cognition following poor sleep, such as experiencing brain fog, difficulty processing information, and lack of motivation:

Efforts to improve sleep largely focused on lifestyle changes and sleep hygiene practices, such as sleep regularity, avoiding foods that might disturb sleep, and managing stress and emotions. However, participants were keen to seek advice about good sleeping practices and often were unsure about healthy sleeping practices:

However, some participants doubted whether sleep had benefits:

Overall, while some participants were aware of its importance or impacts, sleep was not universally recognized by the participants as a core component to cognitive or brain health.