Subjective Sleep Quality Monitoring with the Hypnos Digital Sleep

Diary: Evaluation of Usability and User Experience

Tudor Văcărețu

, Nikolaos Batalas

, Begum Erten-Uyumaz

, Merel van Gilst

1,2

Sebastiaan Overeem

1,2

and Panos Markopoulos

Eindhoven University of Technology, Den Dolech 2, Eindhoven, The Netherlands

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

aret

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

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

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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.).

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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:

 0–7 = No clinically significant insomnia

 8–14 = Subthreshold insomnia

 15–21 = Clinical insomnia (moderate

severity)

 22–28 = 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-

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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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