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CLINICAL REPORT
Measurement of Nocturnal Scratching in Patients with Pruritus
Using a Smartwatch: Initial Clinical Studies with the Itch Tracker App
Akihiko IKOMA 1,2 , Toshiya EBATA 3 , Laurent CHANTALAT 2 , Kimitoshi TAKEMURA 2 , Fabienne MIZZI 4 , Michel PONCET 4 and
Didier LECLERCQ 2
1
Department of Future Design, Maruho Co., Ltd, Osaka, Japan, 2 SHIELD Center, Nestlé Skin Health SA, USA, 3 Chitofuna Dermatology Clinic,
Setagaya, Tokyo, Japan, and 4 Research and Development, Galderma SA, France
Three clinical studies were conducted to test a newly-
developed app for smartwatches, which included an
algorithm to measure nocturnal scratching using acce-
leration data. The first study in 5 patients with atopic
dermatitis demonstrated high reliability of the app for
measurement of scratching compared with video mo-
nitoring (positive predictive value 90.2  ±  6.6%, sensi-
tivity 84.6  ±  10.2%, correlation of scratching duration
per h r = 0.851–0.901, p  < 0.001). The second study in
20 patients with atopic dermatitis and 10 healthy vo-
lunteers showed that total scratching duration in pa-
tients was significantly longer than in healthy volun-
teers and correlated positively with Eczema Area and
Severity Index (EASI) scores. In the third study, con-
ducted in an open-entry manner in which 201 evalua-
ble participants measured nocturnal scratching, those
who self-reported itch or pruritic diseases had a signi-
ficantly longer duration of scratching than those who
did not. In conclusion, this app has a high reliability
and potential clinical usefulness for measurement of
nocturnal scratching.
Key words: actigraphy; itch; scratching; atopic dermatitis;
smartwatch.
Accepted Dec 6, 2018; E-published Dec 6, 2018
Acta Derm Venereol 2019; 99: 268–273.
Corr: Akihiko Ikoma, Department of Future Design, Maruho Co., Ltd., 1-5-
22, Nakatsu, Kita-ku, Osaka, 531-0071, Japan. E-mail: ikoma_eom@mii.
maruho.co.jp
I
tch is a major symptom associated with various der-
matological, systemic and neurological conditions.
Chronic itch seriously impairs the quality of patients’
life. Itch is usually evaluated by patients using subjective
scales, such as a visual analogue scale (VAS) in clinical
settings. The lack of objective quantitative methods to
evaluate itch makes it difficult to evaluate itch severity
during sleep, especially in small children and elderly
people with cognitive impairment, and hence difficult
to precisely assess the efficacy of antipruritic therapies.
Since itch provokes the desire to scratch, measurement
of scratching can be used to indirectly, but objectively,
evaluate itch intensity. There have been attempts to
measure scratching by various methods, such as video-
monitoring, acoustic assessment and measurement of
body movements (1–3). The most frequently applied
method is the measurement of wrist movement, or ac-
doi: 10.2340/00015555-3105
Acta Derm Venereol 2019; 99: 268–273
SIGNIFICANCE
This paper reports 3 clinical studies to measure scratching
in patients with chronic itch, using a new app developed for
use in widely-used smartwatches. The results indicate that
the smartwatch app is reliable and useful for measurement
of scratching during sleep, enabling the indirect, but objec-
tive, evaluation of itch severity. The app has potential for
use in daily clinical settings.
tigraphy (4). A large variety of actigraphy devices has
been used, some of which are marketed as products for
sleep assessment (5–9). Their common feature is that
acceleration signals produced by wrist movement are
recorded by a wristwatch-like device equipped with a
built-in accelerometer, followed by analysis of data to
quantify scratching. Some recent studies have attemp-
ted to differentiate signals caused by scratching signals
from those caused by other types of movement, using
a specific algorithm to accurately quantify scratching
activity (10–12). However, all of the above actigraphy
devices have been produced for specific purposes of
measurement and are not general smartwatches that are
widely used, thus hampering the spread of this method
for daily use.
In the studies reported here, a newly-developed app-
lication software (app) containing a unique algorithm,
termed “Itch Tracker”, was installed into an Apple Watch
(Apple Inc., Cupertino, USA), one of the most widely-
used smartwatches worldwide, and used for measurement
of scratching during sleep. ResearchKit, an open-source
framework offered by Apple Inc. for medical research
using mobile devices, was used to collect data from a
large number of participants.
METHODS
Study objectives
A total of 3 clinical studies were conducted. The first study (Study
1) was conducted to verify the reliability of the app for measu-
rement of nocturnal scratching compared with video monitoring.
The second study (Study 2) was conducted to compare patients
with atopic dermatitis and healthy volunteers with regards to
nocturnal scratching measured by the app. The third study (Study
3) was conducted in an open-entry manner, with anonymous
users of smartwatches worldwide who downloaded the app from
the service site (App Stores, Apple Inc. USA) and installed it on
This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta
Journal Compilation © 2019 Acta Dermato-Venereologica.