Subjective Sleep Quality Monitoring with the Hypnos Digital Sleep
Diary: Evaluation of Usability and User Experience
Tudor Văcărețu
1
, Nikolaos Batalas
1
, Begum Erten-Uyumaz
1
, Merel van Gilst
1,2
,
Sebastiaan Overeem
1,2
and Panos Markopoulos
1
1
Eindhoven University of Technology, Den Dolech 2, Eindhoven, The Netherlands
2
Kempenhaeghe Center for Sleep Medicine, Sterkselseweg 65, Heeze, The Netherlands
Keywords: Usability, User Experience, Digital Sleep Diary, Hypnos.
Abstract: Sleep diaries are records of individual’s sleep and wake times, extending over a period of several days up to
several weeks. Sleep diaries are often used to support the diagnosis and treatment of sleep disorders though
the emergence of self-tracking technologies also makes them interesting for intrinsically motivated
individuals who wish to gain insight into their sleep patterns and related influences. This paper introduces
Hypnos, a digital sleep diary, and a user study aimed to its usability and the resulting user experience. The
study involved eighteen participants without a diagnosed sleep disorder for a period of ten days. Overall
Hypnos was found useful and usable which supports its application in practice, but it is advisable to make the
user experience more attractive, stimulating and innovative in order to also make the self-tracking more
intrinsically motivating.
1 INTRODUCTION
One third of our lives is spent sleeping. Sleep is the
activity that occupies most of our time. However,
sleep is not a smooth experience for everyone. In a
study (Van de Straat, 2015), an average of 24.2 % of
total European population reported to have been
bothered by sleep problems in the past six months.
Sleep problems are disruptions in the systematic
functioning of sleep which further has an impact on
the normal physical, mental, social and emotional
functioning of individuals.
Sleep problems are identified by specialists and
categorised under several classes of sleep disorders.
In order to diagnose and treat sleep disorders, sleep
diaries, among other tools have been invented. Sleep
diaries are records of individual’s sleeping and
waking times during a period of several days up to
several weeks. The information can be written as text
or can be represented graphical, and requires to be
structured in accordance with the framework of the
diary. They are often used in clinical setups for
diagnosing and treating sleep disorders, but they can
also be used by individuals to be more aware of their
sleep experience and to monitor parameters that relate
to their sleep. There are many sleep diaries in use by
specialized sleep disorders clinics, each of them with
its own framework for filling in the data in the diary.
Paper sleep diaries have a few shortcomings to
mention: they do not prevent filling in extraneous
information outside the framework (e.g., comments,
and events other than those expected), it is not
possible to know when the diary has been filled in
(e.g. a patient can complete the paper diary for a
whole week the day before seeing the physician),
paper documents can be easily lost, etc.
Given the high adoption of mobile devices and given
that today’s state of the art mobile devices have large
memory storage, high computational power, built in
sensors and advanced connectivity possibilities it is
likely that pen-and-paper diaries will become a tool
of the past, making way to electronic sleep diaries.
According to a recent study (Zenith, 2017), in 2018
66% of individuals from fifty-two key countries will
own a smartphone, an increase of 3% from 2017 and
8% increase from 2016 tablet ownership is stabilising
at 20% of the population, partly because they are
more likely to be shared in households, and partly
because consumers prefer to user larger smartphones
instead.
The purpose of this paper is to describe the design of
Hypnos, a digital sleep diary, and to discuss the
V
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u, T., Batalas, N., Erten-Uyumaz, B., van Gilst, M., Overeem, S. and Markopoulos, P.
Subjective Sleep Quality Monitoring with the Hypnos Digital Sleep Diary: Evaluation of Usability and User Experience.
DOI: 10.5220/0007407601130122
In Proceedings of the 12th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2019), pages 113-122
ISBN: 978-989-758-353-7
Copyright
c
2019 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved
113
results of the usability and user experience
evaluation.
2 RELATED WORK
The initial diagnosis of sleep disorders is traditionally
made by a primary care physician (Blake, 2010). If
needed, the primary care physician will guide the
patient towards a specialised institution that will have
the expertise to provide adequate treatment.
Sleep specialists use sleep diaries for tracking
patterns of sleep, usually for a period of fourteen
nights. Currently sleep diaries are mostly paper based.
There are many such sleep diaries in use. One such
diary is Karolinska Sleep Diary (Akerstedt, 1994).
This diary contains twelve items, of which most of
them offer a scale graded from five to one. Sleep
diaries are valuable tools for the assessment of sleep
because they provide a subjective overview of the
patient’s sleep, they are inexpensive, efficient and
validated clinical tools. Even when objective data is
possible to obtain through modern sensing solutions,
this does not help understand the subjective
experience and complaints of people. For this
reasons, subjective report of sleep quality is still
indispensable.
Some health clinics treating patients diagnosed with
sleep disorders use sleep diaries written by them from
scratch. However, this makes it difficult to compare
patient data and related practices. For this reason an
expert panel of twenty-five attendees of Pittsburgh
Assessment Conference have attempted to align and
standardize these sleep diaries and proposed the
Consensus Sleep Diary (Carney, 2012). The
Consensus Sleep Diary is a table of nine text items
which patients have to record daily over a period of
time. The items that the diary measures are the
following:
1. What time did you get into bed?
2. What time did you try to go to sleep?
3. How long did it take you to fall asleep?
4. How many times did you wake up, not counting
your final awakening?
5. In total, how long did these awakenings last?
6. What time was your final awakening?
7. What time did you get out of bed for the day?
8. How would you rate the quality of your sleep?
9. Comments.
(Carney, 2012)
The items are presented in a tabular format, requiring
the participant to record times, (items 1-7), using a
rating scale (item 8) and inserting free text (item 9).
These information entry tasks can be tedious which
can only diminish adherence. For this reason, it be-
Figure 1: Paper-based sleep diary used at Kempenhaeghe Center for Sleep Medicine. The text in black is in Dutch language
and the text in red represent English translations.
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Figure 2: Initial sketch of the sleep diary concept and a screenshot from the first version of sleep diary tool.
comes interesting to use graphical formats for
entering the same which trade off the precision of
entry (e.g., entering the exact minute of going to bed),
with an ease of use and an intuitive presentation of the
information. Such an approach has been developed
and is used at Kempenhaeghe Center for Sleep
Medicine as seen in Figure 1. This sleep diary uses a
graphical timeline for each day on which the patient
has to enter the data about the previous night’s sleep.
One A4 single-sided page spans seven days, which
makes it easy for the somnologist to get an overview
and identify the sleep patterns of the patient over a
period of one week. At least two weeks of data are
required from the patient, but it can also be that
patients will deliver more weeks of data due to
waiting times before the patient is scheduled for the
visit. The patient can mark on the timeline the
following information:
1. Date.
2. Time settled in bed.
3. Time patient got out of bed.
4. Sleep (Marked with a full cross-hatching on the
paper).
5. Awake in bed (marked with half cross-hatching on
the paper).
6. Time light goes off (marked with a vertical bar).
7. Comments (optional on the back side of the diary).
The patient receives instructions on how to fill in the
sleep diary together with the diary pages. We note
that except for item 8 all items from the consensus
sleep diary are also encountered in the sleep diary in
use at Kempenhaeghe. While the graphical format
makes entering information and gaining an overview
easier, it still suffers from the limitations of paper
noted in the introduction. Digital diaries overcome
these limitations, and while some work has been done
in this direction (Blake, 2010), none of the digital
diaries to our knowledge feature a graphical input that
would facilitate an easier and more pleasant
experience for filling in such a diary. For this reasons,
a digital version of this diary has been designed and
evaluated.
3 THE HYPNOS DIGITAL SLEEP
DIARY
Hypnos was developed in an effort to digitize and
improve the sleep diary in use at Kempenhaeghe
described above. Advantages of digital data
collecting tools are numerous. The interface
emphasizes the visual representation of data to enable
easy logging of data and build on the human innate
ability to perceive complex visual scenes fast
(Thorpe, 1996). Hypnos was developed using the
Ionic Framework, a mobile application development
framework that allows targeting multiple platforms
with one code base. Ionic, based on Apache Cordova,
allows the production of hybrid web apps that target
both Android and iOS platforms from a single
codebase. Even more, the app can run as a web
application as well, given that the languages used by
the framework are HTML, CSS and JavaScript.
Digitizing the diary can help ensure the integrity of
the self-reported information, which is essential for a
precise diagnosis and treatment. Possible input errors
such as filling in an amount of sleep that exceed the
amount of time spent in bed are possible with the
traditional pen and paper sleep diaries. For this the
digitized interface of Hypnos makes the time slot
obvious for a user, thus making this type of error not
possible. Following the design of the graphical paper
diary, the timeline is divided into fifteen minutes time
slots to enhance ease of entering information note
that more precision in the timeline (e.g. 1 minute time
slots) would not necessarily correspond with how
well patients can recall the sleep times.
The user interface was designed in an iterative
fashion. Paper mock-ups like those shown in Figure 2
were discussed with five behavioral therapists
specialized in the treatment of sleep-related disorders.
Subjective Sleep Quality Monitoring with the Hypnos Digital Sleep Diary: Evaluation of Usability and User Experience
115
Figure 3: Final user interface for Hypnos application.
The design received positive reactions, e.g., a
behavioral therapist found the way of registration
easy to use and natural and commented: “It is like you
are colouring it yourself.”
In the first designs, sleep parameters (e.g. sleep
efficiency, wake after sleep onset) were not displayed
to users. Following expert feedback it was decided to
focus on the interface on sleep logging to make the
tool generic and simple to use. Further additions were
made to align the tool with clinical practice: naptimes
are added as a separate entry, and finally, lights on
and off feature are added.
The functionality of Hypnos is divided into two main
features: Record Data and View Data. These two
options are displayed as the start point in the
application. Record Data will open an empty
timeline. Here, users are allowed to input the
following sleep states: awake in bed, asleep,
daytime nap, awake out of bed. Additionally
lights off and lights on timeline markers have to
be placed at the corresponding time on the timeline.
Users have to select one of the four states and select
timeslots with a swipe gesture on the desired time
slots thus making it easy and interactive to fill in the
diary by colouring time slots through simple gestures.
Awake out of bed, a sleep-related state itself can be
perceived as an erase action on the timeline. After
participants finished inserting data on the timeline,
they can save the data by pressing the “done editing”
button. If a user realizes that data has not been
inserted correctly, they can re-edit data by pressing
the edit button. Sleep data can be inserted only for the
previous day, thus ensuring quality of the self-
reported subjective sleep data. Users can go back to
the start screen by pressing the go back arrow located
in the top-left side of the screen. If users press the
View Data button a new screen will open
displaying a grid of sleep diary entries. The users can
select a particular entry, by tapping on it. A new
screen will open displaying the sleep timeline for the
particular day as well as the following sleep
parameters: total time asleep, total time awake in bed,
total time fully awake, total time in bed, total time
napping, wake after sleep onset, sleep efficiency and
sleep latency.
3.1 Application Workflow
The application workflow is depicted in Figure 4.
Hypnos has six different screens: Splash screen,
Choose Action, Record Data, View Data, Saved Data
and View Sleep Diary Entry. Each screen is briefly
described below:
1. Splash Screen is displaying a detail of the painting
Starry Night by Dutch painter Vincent Van Gogh
while the application is loading.
2. Choose Action screen displays two options the user
can choose from: Record Data or View Data.
3. Record Data screen shows an empty twenty-four
hour timeline, spanning over two days, with the mid-
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Figure 4: Application workflow.
night located in the middle. The reason for this is to
facilitate inserting of sleep data over one timeline. If
the timeline would be displayed between 00:00
23:59 most users will have to input sleep data over
two separate timelines.
4. Saved Data is shown after the user has finished
inserting data, and has saved data by pressing done
editing” button.
5. View Data screen displays a grid of sleep diary
entries. The user can select one of the entries.
6. View Sleep Diary Entry shows recorded data of a
certain day, together with the associated sleep
parameters (sleep efficiency, sleep latency, total time
asleep, etc.).
Subjective Sleep Quality Monitoring with the Hypnos Digital Sleep Diary: Evaluation of Usability and User Experience
117
4 USABILITY STUDY AND USER
EXPERIENCE STUDY
A field trial of Hypnos was conducted with the aim to
provide a summative evaluation of its usability (ISO,
2018) and of the emerging user experience (Law,
2012). Usability in this context is vital for ensuring
the quality of the collected data, reduce the workload
of the users and thus enhance adherence. Whereas
usability captures aspects such as ease of learning and
ease of use, we are also interested in a more holistic
understanding of all aspects of the end-user’s
interaction with the product, which is captured by the
concept of user experience. As a secondary
(formative) objective we set out to identify
opportunities for improving Hypnos.
4.1 Research Plan
The research took place in different stages. For a
visual description of the different stages please refer
to Figure 5. The first stage of the study required that
participants used the application and got accustomed
with Hypnos by following a set of tasks. Participants
were required to accomplish the tasks in laboratory
setting with think-aloud method (Nielsen, 1993) and
researchers observed participants’ interactions with
Hypnos, which further allowed to gain qualitative
data regarding usability issues in Hypnos application.
The task list the participants had to complete was as
follows:
1. Locate the app icon and open the app.
2. Open Record Data functionality in the app.
3. Input when lights went off in their bedroom the
previous night.
4. Input when lights went on in their bedroom the
previous night.
5. Fill in nap times of the previous day.
6. Fill in the times he/she was asleep the previous
day.
7. Fill in the times he/she was awake in bed the
previous day.
8. Fill in the times he/she was awake out of bed the
previous day.
9. Save the data in the diary.
10. View saved data.
After completing the predefined task list participants
were required to complete the System Usability Scale
questionnaire (Brooke, 1996) and Insomnia Severity
Index questionnaire (Morin, 2011). Afterwards
participants were given a Lenovo Tab3 7 Essential
tablet, with a screen resolution of 1024X600 and 7”
screen size, or a Samsung S8 smartphone with a
Figure 5: Research plan divided in the different stages.
screen resolution of 2960 X 1440 pixels and 5.8”
screen size to take at home with Hypnos application
installed. In total nine tablets and nine smartphones
were distributed. It was required that they fill in a
sleep diary daily for ten days, after which the second
assessment took place. The next stages took part
during the post-study session. During this session,
participants handed in the devices to researchers and
answered questions in an exit interview. The
interview was semi-structured and audio recorded.
Researchers took notes during the interview and
referred back to the audio recording when needed.
The information from the interview was grouped in
items participants liked about the sleep diary, items
participants did not like about the sleep diary, and
recommendations for improvements that participants
made.
After the interview participants filled in the User
Experience Questionnaire (Laugwitz, 2008) and the
Insomnia Severity Index questionnaire for a second
time.
4.2 Measures
Three questionnaires were used as means of
conductive quantitative research, and observation of
user interaction and an exit interview were the means
of conductive qualitative research.
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4.2.1 Insomnia Severity Index (ISI)
The Insomnia Severity Index is a brief screening
assessment tool designed to evaluate insomnia
through seven Likert style rating scales with scores
ranging from zero to four. The scores are added up
and interpreted as follows:
07 = No clinically significant insomnia
814 = Subthreshold insomnia
1521 = Clinical insomnia (moderate
severity)
2228 = Clinical insomnia (severe)
The ISI is one of the most widely used assessment
instrument in clinical and observational studies of
insomnia. It was adopted in order to track self-
perceived sleep problems before and after using the
sleep diary and to verify the stratification of
participants sleep issues - as it was not intended to
include only problem sleepers in the study.
4.2.2 System Usability Scale (SUS)
Usability was evaluated with SUS, a short and widely
used questionnaire which consists in ten rating scales
ranging from 0 to 10. By adding up ratings an overall
usability score from 0 to 100 can be derived. (Brooke
1996). Given the wide use of SUS it is possible to
compare the ratings for any particular system to data
collected from 446 studies with over 5000 individual
SUS responses, the overall mean SUS score for this
data set was 68 with a standard deviation of 12.5.
(Sauro, 2012).
4.2.3 User Experience Questionnaire (UEQ)
The main goal of the UEQ is to deliver a fast
measurement considering aspects of pragmatic and
hedonic quality.
The User Experience Questionnaire is a 26-item
questionnaire used for measuring the subjective
perceived user experience of artefacts. The reliability
of UEQ scale is quite high with Cronbach-Alpha
coefficient typically greater than 0.7 (Santoso, 2016).
The 26 items measure user experience aspects
grouped in six subscales:
Attractiveness: Overall impression of the
product. Do users like or dislike it?
Perspicuity: Is it easy to get familiar with the
product and to learn how to use it?
Efficiency: Can users solve their tasks
without unnecessary effort? Does it react
fast?
Dependability: Does the user feel in control
of the interaction? Is it secure and
predictable?
Stimulation: Is it exciting and motivating to
use the product? Is it fun to use?
Novelty: Is the design of the product
creative? Does it catch the interest of the
users?
4.3 Participants
For the evaluation of Hypnos 18 participants (5 male
and 13 female) were recruited and invited to
participate in the study with a mean age of 29.4 years
(SD = 3.39). Recruitment took place at the
department of Industrial Design of Eindhoven
University of Technology. Researchers invited
master and doctoral students to take part in the
evaluation study. Each participant was involved in the
study for ten days: a forty-five minutes pre-trial
session, ten days trial period of Hypnos and one post
trial session of forty-five minutes. Participants gave
informed consent and were rewarded after the study
with a ten Euro voucher at an online book store.
5 RESULTS
5.1 Results of the Quantitative
Assessment
5.1.1 Results from the System Usability
Scale (SUS)
Hypnos received a mean usability score of 74.58
(SD=9.36). Scores were very similar for participants
using phones (M=74.4 , SD = 8.64) and participants
using tablets (M = 74.72, SD = 10.56).
A One-Sample T Test showed that participants
evaluated the usability with the SUS questionnaire
significantly higher than the population average of
68, t(17) = 2.98 , p = .008. By referring to the
conversion table of SUS scores to percentile ranks
that can be found in (Sauro, 2012), it can be deducted
that Hypnos can be considered more usable than 70%
of the products in the Sauro database and less usable
than 30%.
5.1.2 Results from the User Experience
Questionnaire (UEQ)
All eighteen participants completed the UEQ
questionnaire after the experiment period of ten days.
The results of the UEQ questionnaire are displayed
per scale in Figure 6 (numeric) and Figure 7
(graphical). The UEQ does not produce an overall
score. Values between -0.8 and +0.8 represent a neu-
Subjective Sleep Quality Monitoring with the Hypnos Digital Sleep Diary: Evaluation of Usability and User Experience
119
Figure 6: Results of UEQ (numeric).
tral evaluation of the corresponding sub-scale, values
> +0.8 represent a positive evaluation and values < -
0.8 represent a negative evaluation. The range varies
between -3 (horribly bad) to +3 (extremely good). It
is extremely unlikely to obtain values over +2 or
lower than -2, thus even a quite good value of +1.5
looks visually not as positive as it is on a scale from -
3, +3 (Santoso, 2016).
Figure 7: Results of UEQ (graphical).
By looking at the results, it can be observed that only
the hedonic dimensions show neutral values:
Stimulation (M=0.65, SD=0.72) and Novelty
(M=0.02, SD=0.76). This was expected as the
purpose of Hypnos was to offer a simple and practical
digitized version of a sleep diary, that could be used
in clinical context rather than an engaging user
experience. Not to be ignored, hedonic traits need
further investigation and research to provide input for
further iterations of Hypnos that will finally fulfil
these characteristics as well. Perspicuity, Efficiency
and Dependability mean values represent a positive
evaluation, while Attractiveness is borderline and can
still be improved in future iterations.
5.1.3 Results from the Insomnia Severity
Index (ISI)
Only 17 participants were included in the test, as one
participant did not fill in one of the two ISI
questionnaires. Descriptive statistics show that for the
pre-experiment ISI questionnaire trial (M=8.58,
SD=6.08), and for the post-experiment ISI
questionnaire trial (M=9.17, SD=6.51). A Wilcoxon
Signed-Ranks Test was carried out using SPSS on the
pre and post study ISI results and indicated no
statistically significant results with Z=.492, p<.623,
therefore no conclusions can be drawn.
5.2 Results of the Qualitative
Assessment
5.2.1 Observations during Onboarding
Except two participants, everyone involved in the
study completed the ten tasks described in 4.1 with
minimal help from the researchers (the sleep diary did
not have a user manual at the time of the evaluation
therefore a researcher was available for help in case
participants would get stuck). One of the most
commonly encountered issue during the onboarding
of the application concerned erasing data in the sleep
diary. Because there was no erase or delete icon in the
application, and because the awake out of bed icon is
completely white, and does not refer to a delete or
erase action, participants found it difficult to map this
icon to the action of erasing. Lights on and “lights
off markers on the timeline of the application were
also not clear for participants and required further
explanations on how to set markers in relation to their
sleep experience.
5.2.2 Exit Interview Results
The exit interview had the main purpose of collecting
qualitative data.
The data gathered during the interview was grouped
in three categories: Pleasant, Unpleasant and
Improvements. Below we present some of the
pleasant, unpleasant and improvements points
collected through qualitative research.
Pleasant
One of the most encountered feature participants
mentioned as pleasant was that the simplicity of the
app. After the onboarding the functionality was clear
for the participants and they did not encounter
problems while filling in data at home in the sleep
diary. Another encountered item mentioned by
participants was that they were more aware of their
sleep routines and that they could plan their sleep
better because of this. One of the participants also
mentioned that filling in the diary is quite fun and
practical, and that after a certain period of time it
becomes a habit: “It’s quite practical actually, and
because I record all my data every single day, it made
me have this behaviour to be more aware of how my
sleep is in the recent ten days, so I have an overview
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of my sleep status. And it is quite fun to use”. Also,
the simplicity in interaction to fill in the diary was
mentioned by participants.
Unpleasant
During the exit interview most of the participants
complained about the size of the slots in the timeline
they had to fill in. For example, one participant
mentioned he felt he had a fat finger, because he could
not precisely select the correct time slot without
zooming: ”…like I said, the feeling of having a fat
finger that encroaches on other things, that was the
only real frustration that I had with it...”. Other
participants complained that they felt under pressure
to fill in the sleep diary “…because I must record, so
it is a pressure on me…” and that it is hard to
remember to fill in the sleep diary on time.
Improvements
Participants suggested that offering a better overview
of their data that would include meaningful
visualisations and patterns would be desirable.
Participants also mentioned that they would like to be
able to add comments on the data they filled in, e.g.,
to note reasons on why they woke up at night:
“…maybe when you wake up at night, that you can
indicate why…”, or what was the reason for which
they needed to take a nap in the afternoon. Some
participants also noted that zooming and scrolling on
the timeline was difficult. A few participants
mentioned the wish of being able to see more diaries
on one page. This way a pattern of their sleep
behaviour could be better observed. Other
improvements suggested by participants are:
reminders, recording mood of the day, recording
objective data such as location of sleep, snooze events
as well as self-reported information like the
description of dreams.
6 CONCLUSIONS
Hypnos is a graphical digital diary that allows to
report easily sleep data traditionally captured in paper
diaries. Its design emphasizes simplicity and supports
an overview of sleep data that can be useful to
clinicians as well to researchers.
The results of the quantitative assessment were not
unexpected. The usability of the app was evaluated
positively. The user experience evaluation found
positive scores with regards to pragmatic aspects of
the user experience (perspicuity and usefulness), but
showed that the device could be made more engaging
and innovative. This enforces that the next steps
needed to be taken in the following iterations of
Hypnos should be in the Stimulation and Novelty
dimensions defined by the UEQ questionnaire. The
qualitative assessment results identified several
usability and user experience issues that need more
consideration. By addressing them, we can only
expect that usability and user experience will
improve.
For these reasons, Hypnos would need another
iteration for addressing the identified issues, and
conduct a final usability and user experience with
both clinicians and patients before positioning it as a
clinical tool.
In terms of study limitations, we are aware of the fact
that the participants recruited were on average
younger than our potential target population, highly
educated and healthy. Being in a highly educated
young age segment of the population, it is more likely
that they are digital native, proficient with tablets and
smartphones, and learn quicker than seniors.
Both clinical practice and research need such a tool
for multiple reasons. It is clear that digital sleep
diaries have advantages over traditional pen and
paper diaries such as: data input validation, collecting
quality data, higher adherence, safe storage and a
better user experience. Both clinicians and patients
would benefit of such advantages, with the end result
of a better treatment. Researchers by potentially
having access to big data collected through time can
conduct higher quality research and process data
easier. Therefore, based on this study, the authors
propose to run another development iteration of
Hypnos that will improve the usability and enhance
user experience of the app which will further be tested
and validated.
ACKNOWLEDGEMENTS
This research was performed within the Eindhoven
MedTech Innovation Center (e/MTIC, a
collaboration between Kempenhaege Center for
Sleep Medicine, Eindhoven University of
Technology, and Philips Research). Development
and evaluation of the sleep diary was done within the
project: HealthBed: Unobtrusive monitoring of
health-related parameters in the bed environment,
funded by a EIT Health grant (no. 17092).
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