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Self-reported alcohol misuse remains high in armed forces personnel even after they have left service. More than 50% of ex-serving personnel meet the criteria for hazardous alcohol use; however, many fail to acknowledge that they have a problem. Previous research indicates that interventions delivered via smartphone apps are suitable in promoting self-monitoring of alcohol use, have a broad reach, and may be more cost-effective than other types of brief interventions. There is currently no such intervention specifically designed for the armed forces.
This study sought to describe the development of a tailored smartphone app and personalized text messaging (short message service, SMS) framework and to test the usability and feasibility (measured and reported as user engagement) of this app in a hard-to-engage ex-serving population.
App development used Agile methodology (an incremental, iterative approach used in software development) and was informed by behavior change theory, participant feedback, and focus groups. Participants were recruited between May 2017 and June 2017 from an existing United Kingdom longitudinal military health and well-being cohort study, prescreened for eligibility, and directed to download either Android or iOS versions of the ”Information about Drinking for Ex-serving personnel” (InDEx) app. Through the app, participants were asked to record alcohol consumption, complete a range of self-report measures, and set goals using implementation intentions (if-then plans). Alongside the app, participants received daily automated personalized text messages (SMS) corresponding to specific behavior change techniques with content informed by the health action process approach with the intended purpose of promoting the use of the drinks diary, suggesting alternative behaviors, and providing feedback on goals setting.
Invitations to take part in the study were sent to ex-serving personnel, 22.6% (31/137) of whom accepted and downloaded the app. Participants opened the InDEx app a median of 15.0 (interquartile range [IQR] 8.5-19.0) times during the 4 week period (28 days), received an average of 36.1 (SD 3.2) text messages (SMS), consumed alcohol on a median of 13.0 (IQR 11.0-15.0) days, and consumed a median of 5.6 (IQR 3.3-11.8) units per drinking day in the first week, which decreased to 4.7 (IQR 2.0-6.9) units by the last week and remained active for 4.0 (IQR 3.0-4.0) weeks.
Personnel engaged and used the app regularly as demonstrated by the number of initializations, interactions, and time spent using InDEx. Future research is needed to evaluate the engagement with and efficacy of InDEx for the reduction of alcohol consumption and binge drinking in an armed forces population.
Alcohol misuse is common in the United Kingdom (UK) armed forces and the prevalence is higher in the military than in the general population [
Most people in the general population underestimate their drinking and do not perceive it as problematic, even when the level of consumption is potentially harmful to health [
In the last decade, computer and Web-based interventions (eg
There are a large number of alcohol-related apps available to the general population with a recent content analysis identifying more than 600 apps, of which 91 were identified as focusing on alcohol reduction [
Most existing alcohol apps include self-monitoring (eg
We are not aware of any mobile health app that seeks to customize a brief alcohol intervention using personalized SMS text messages. In this study, we describe the development of the “Information about Drinking for Ex-serving personnel” (InDEx) mobile phone app, a tailored 4 week (28 day) intervention specifically designed to target ex-serving personnel who meet the criteria for hazardous alcohol use, which is likely to impact on their functioning. The purpose of this study was to design an engaging, responsive, and usable smartphone app that delivers personalized SMS text messages and gathers alcohol usage data and to test the usability and feasibility, measured and reported as user engagement, of this app in a hard-to-engage ex-serving population. Our primary outcome measure was adherence with InDEx, which was measured by the number of weeks participants engaged with the app. Our secondary outcome measures were how many times participants used the app (eg
Potential participants were eligible for inclusion if they had served in the UK military, were aged 18-65 years, owned an iPhone or Android device released after 2012, were willing to receive daily SMS text messages, currently resided in UK, and were capable of providing informed consent. Those who had an AUDIT score lower than 8 or greater than 19 were excluded because InDEx is focused on intervening among those drinking hazardously or harmfully, who are likely to be experiencing short-term consequences of their drinking, yet unlikely to be seeking any treatment for this misuse. Those scoring above 20 on the AUDIT meet criteria for probable alcohol dependency and we felt that they may require more intensive treatment. Potential participants took part in the King’s Centre for Military Health Research cohort study [
Design and development of the InDEx app was undertaken on an Apple MacBook Pro, 2.5 GHz i5 Intel processor and 8GB RAM. Drifty Co IONIC Framework version 1 [
A full description of the development process, including the InDEx app source code, is available in [
The development of the InDEx app was academic-led and supported by experts in smartphone app development, epidemiology, addiction psychiatry, and military mental health. The content of the intervention incorporated effective components of previous electronic alcohol interventions (eg, [
Stage 1: Normative feedback (defined below), action self-efficacy, and self-monitoring
Stage 2: Maintenance of self-efficacy and action planning
Stage 3: Recovery of self-efficacy and coping planning
The features were grouped into the following modules:
Account Management: Participants can modify personal information (eg, first name, last name, and mobile number), password, and app parameters (eg, automatic log-out and clear local storage).
Assessment and Normative Feedback: Captures the participant’s response to a set of questions (defined by the research team) and aggregates responses to produce an infographic representing the participant’s alcohol consumption in comparison to the general population.
Self-monitoring and Feedback: Records alcohol consumption by participants and provides a range of visual (eg, charts, figures, and text) metrics to allow for monitoring of consumption.
Goal (setting and review): Participants can set goal(s) based on the implementation intentions [
SMS Text Messaging (review): Provides a facility to review SMS text messages sent to and from the InDEx central server system. Further, participants can rate automated SMS text messages (5 star Likert rating).
The app was developed using Agile development methodologies [
To create an account, a participant was required to provide their first name, last name, email address, mobile telephone number, username, password, and in-app informed consent. All sensitive information such as password was encrypted using Bcrypt hashing algorithms (salt factor 10).
InDEx app is presented in
Example screenshots of interactions with the InDEx app (left to right, beginning at top): normative feedback, personalized text message history, set a goal, drink diary, dashboard and add a drink. Source: King’s Centre for Military Health Research, King’s College London.
In UK, 4 out of 5 adults own a smartphone; among 18-44-year-olds, adoption is higher at 91% [
The InDEx app was complemented by tailored SMS text messaging that provides prompts to use the drinks diary, suggests alternative behaviors, and provides feedback on goals. A bank of 180 tailored SMS text messages was developed in line with delivery stages (defined earlier), which were informed by the HAPA framework and from discussion groups with ex-serving personnel to further refine the messages (
InDEx uses baseline and contiguous measurements to inform the type of SMS text messages a participant receives to provide a participant-centric approach. Baseline measurements are used to identify suitable messages and as a participant engages with InDEx, continuous measurements are used to reflect current behavior and attitude; for example, if a participant reports feeling depressed or anxious (measured by the patient health questionnaire [
SMS text messages and two-factor authentication codes (used to verify the participant’s mobile phone number) were sent automatically using Twilio’s Application Programming Interface via InDEx central command servers. No human involvement was required. All SMS text messages sent to participants were visible in the app (“My Messages” page). Participants could rate any message (rating scale 1-“poor” to 5-“excellent”) and provide SMS text message responses, which were stored and displayed to the user but not monitored by the study team.
InDEx was submitted to the Google Play and Apple iTunes App stores via Google Play Developer Console and Apple iTunes Connect, respectively. For testing of InDEx, a private testing group was created; only those who had been given permission were able to access and download InDEx.
All measurements were collected via the modules, as seen in
Upon successful registration (referred to as “day 0”), participants completed several baseline questionnaires that collected the following information: (1) Age and sex; (2) Alcohol consumption and alcohol use disorders via alcohol use disorders identification test (AUDIT; [
Baseline measurement responses informed the type of SMS text message a participant would receive. Although this was optional, the baseline measures were asked again upon completion of the study (day 28).
Participants were asked on days 8, 15, and 22 to complete GAD-2, PHQ-2, and Readiness to Change and Self-Efficacy Scales. Any response provided by the participant further informed the tailoring of the SMS text messages, for example, a participant who scores low on the Readiness to Change Scale is sent supportive messages to encourage a willingness to change.
Participants could “
An example of the type of
Day to be sent | Type | Related BCTa | Message |
3 | Tailored | Mental rehearsal of successful performance (BCT 15.2)b | Hi {name}, try thinking that if I am at the pub this week and feel like drinking then imagine how fresh I will feel the next day if I do not drink a lot. |
8, 14, 21, 28 | Tailored and triggered | Self-monitoring of behavior (BCT 2.3)b | Hi {name}, have you logged your drinks from last week? It’s quick and easy to do, just go onto the “drinks” tab in the app. |
8 | Generic | Action planning (BCT 1.4)b | Hi {name}, why not set a goal to reduce the amount you drink? It has been found to really help reduce your drinking, you can start now by clicking on the “goals” tab in the app. |
aBCT: behavior change technique.
b
Example screenshots of the InDEx app measurement (questionnaire) module. Source: King’s Centre for Military Health Research, King’s College London.
Participants could optionally provide volume, strength, price, and calories; however, if no information was provided, UK standard data were used [
We measured usability by frequency of engagement using a published procedure [
Participant engagement was tracked using Google Analytics for Mobile which recorded data when the participant was online or offline. It was not possible to confirm and track if a participant read the SMS text messages, except in cases where the participant provided a rating from within the app.
Prior to the study commencing, a risk protocol was developed and approved by the University of Liverpool Ethics Committee. Adverse health events were ascertained via automatic monitoring and reporting based on measurement responses and alcohol consumption. A clinician received all warning notifications, which were predefined by the research team for review. If the clinician felt that the event was clinically significant, participants were offered a call by a clinician (for those who declined, a reason was recorded) to discuss the adverse health event. All participants, irrespective of an adverse health event, were provided with a signposting and pathways to local support and assistance via a “Support” page within the app.
We calculated descriptive statistics to estimate engagement and usability with the app, which were used as a proxy for the feasibility of the InDEx app (to address the primary outcome). Engagement statistics were reported as median and interquartile range (IQR) because the data were not normally distributed (evaluated using skewness and kurtosis values and visualizing the data). Popularity of pages was inferred from the summation of the total number of times each page was viewed by users, and pages were then ranked from highest to lowest number of views.
The average number of drinking days, drink free days, units consumed, units consumed per drinking day, and alcoholic drinks per drinking day were computed across participants and reported as median and IQR. In this study, the number of binge drinking days was computed per week based on the number of days participants reported consuming 6 or more alcoholic drinks (to address the secondary outcome). Self-reported baseline and weekly measurements were presented as median and IQR, except for Readiness to Change and Self-Efficacy Scales, which were presented as mean and SD. Analyses were undertaken using STATA SE 14.2.
Ethical approval was obtained from the local Research Ethics Committee at the University of Liverpool (reference: #0625).
As shown in
Participants used the InDEx app for a median of 4.0 (IQR 3.0-4.0) weeks (primary outcome), initializing 15.0 (IQR 8.5-19.0) times over 4 weeks and engaging in 29.0 (IQR 20.0-40.5) sessions for a median of 48.8 seconds (IQR 35.1-73.1).
In total, 1083 (mean 36.1, SD 3.2) SMS text messages were sent. Participants were able to reply to messages but were informed that responses would not be monitored. There were 18 replies and 42 SMS text message ratings. The mean rating of content suitability was 2.5 (SD 1.3), indicating a neutral rating for the content of those messages. One participant withdrew consent for receiving SMS text messages on day 16 of the study.
Participant flow through the study.
Engagement measures over the study period per participant.
Engagement Measure | Median (IQRa) |
Initializationsb | 15.0 (8.5-19.0) |
Session count | 29.0 (20.0-40.5) |
Session duration (s) | 48.8 (35.1-73.1) |
Interactionsc | 223.0 (182.3-303.5) |
Weeks active | 4.0 (3.0-4.0) |
aIQR: interquartile range.
bApp initialization reflects the app being opened without a background session existing.
cDefined as a participant performing a click event (eg
Top 10 viewed pages within the InDEx app visited by participants within the study period.
Page | n (%) |
Dashboard | 4045 (38.41) |
Drinks diary | 3031 (28.78) |
Add drink | 1160 (11.01) |
Account | 390 (3.70) |
Goals | 379 (3.59) |
Normative feedback | 244 (2.31) |
Weekly assessment | 166 (1.57) |
Login | 148 (1.40) |
Support | 102 (0.96) |
Your messages | 98 (0.93) |
Other pages | 766 (7.27) |
Number of drinking days, drink free days, units consumed, and alcoholic drinks per drinking day across the study period (4 weeks, n=31).
Reported alcohol consumption | Median (IQRa) |
Drinking days | 13.0 (11.0-15.0) |
Drink free days | 15.0 (13.0-17.0) |
Units per drinking day | 4.7 (2.3-9.1) |
Units consumed | 79.4 (58.4-117.3) |
Alcoholic drinks per drinking day | 2.0 (1.0-4.0) |
aIQR: interquartile range.
Drinking behavior of participants over the study period; n denotes number of participants who recorded an alcohol event during the period.
Reported alcohol consumption | Week 1 (n=31), |
Week 2 (n=30), |
Week 3 (n=29), |
Week 4 (n=31), |
Drinking days | 4.0 (3.0-5.0) | 3.0 (3.0-4.0) | 3.0 (3.0-4.0) | 3.0 (2.0-3.0) |
Drink free days | 3.0 (2.0-4.0) | 4.0 (3.0-4.0) | 4.0 (3.0-4.0) | 4.0 (4.0-5.0) |
Units per drinking day | 5.6 (3.3-11.8) | 6.5 (2.3-9.1) | 4.54 (2.3-8.9) | 4.7 (2.0-6.9) |
Units consumed | 22.9 (14.3-32.4) | 20.4 (14.6-25.0) | 18.1 (12.7-26.3) | 15.9 (11.6-26.9) |
Alcoholic drinks per drinking day | 2.0 (2.0-4.0) | 3.0 (1.0-4.0) | 2.0 (1.0-4.0) | 2.0 (1.0-4.0) |
Binge drinking days per weekb | 2.0 (1.0-3.0) | 2.0 (1.0-2.0) | 1.0 (0.0-2.0) | 2.0 (1.0-2.5) |
aIQR: interquartile range.
bDefined as having 6 or more alcoholic drinks in a session.
Self-reported baseline and weekly measurement responses.
Variable | Day 0 (n=31) | Day 8 (n=25) | Day 15 (n=25) | Day 22 (n=21) | Day 28 (n=22) |
Two item Generalized Anxiety Disorder Scale, median (IQRa) | 0 (0-1) | 0 (0-0) | 0 (0-1) | 0 (0-0) | 0 (0-0) |
Two item patient health questionnaire, median (IQR) | 0 (0-2) | 0 (0-0) | 0 (0-1) | 0 (0-0) | 0 (0-0) |
Alcohol use disorders identification test, median (IQR) | 11 (10-12) | N/Ab | N/A | N/A | 10 (8-12) |
Self-efficacy, mean (SD) | 6.7 (2.7) | 5.9 (3) | 4.9 (3.2) | 6.3 (2.5) | 4.5 (3.1) |
Readiness to change, mean (SD) | 4.4 (3.2) | 4 (3.3) | 3.4 (2.8) | 4.9 (3.2) | 3.7 (2.7) |
aIQR: interquartile range.
bN/A: not applicable.
The aim of this paper was to design an engaging, responsive, and usable smartphone app that delivered personalized SMS text messages and gathered alcohol usage data. We tested the usability and feasibility, measured and reported as user engagement, of this app in a hard-to-engage ex-serving population. The InDEx app was codesigned by stakeholders and ex-serving personnel, with the results indicating successful user engagement and adherence. Based on the primary and secondary outcome measures, the participants used the app for the length of the study period, with two-thirds of participants using the app every week and the majority still using it in the final week (27/31, 87%). These engagement measures suggest that participants were highly active in using InDEx during the study period and that it is feasible to collect alcohol consumption data from this population. On average, most participants reported drinking on just under half of the days in the study period with participants reporting binge drinking on average 2 times a week. Reductions in units per drinking day and units consumed per week were observed across this 4 week study (yet the average number of drinks remained consistent); however, it is not possible to determine whether this may be due to participants changing the size and alcohol content of their drinks in this small feasibility study.
In this study, the most frequently opened page was the “Dashboard,” the “Drinks Diary” page was the second most frequently accessed, and the “Add Drinks” page was third. The top 3 most viewed pages accounted for 78.20% (8236/10529) of all app views, indicating that most participants used the InDEx app primarily for monitoring drinks and the other features were not used as frequently. InDEx offered the ability to set a goal using an if-then format; however, participants used this feature rarely even after encouragement to set a goal via SMS text message and in-app prompts. This may be due to the sample not believing that they have a problem or being unable to navigate to and set a goal, which will be explored further in future work.
We applied behavior change theory [
InDEx has features not offered in other currently available alcohol apps [
To the authors’ knowledge, this was the first study to use SMS text messages embedded in an app to specifically focus on improving engagement and alternative behavior related to the individual alcohol consumption of ex-serving personnel. Although several studies have sought to investigate the impact that SMS text messages and tailoring can have on adherence, the combined use of the 2 strategies within the framework of a mobile app has never been attempted before.
Notwithstanding the study strengths, our findings have some limitations. First, the baseline weekly alcohol consumption data were self-reported, albeit using reliable, consistent, and “gold standard” measurements. As with all self-report measures, recall and social desirability biases may have impacted responses to be more favorable than if collected using objective methods, such as transdermal alcohol monitoring [
In summary, the results of this study suggest that the InDEx app was feasible to implement and acceptable to participants, who typically engaged with the app for most of the study duration. It was feasible that participants reduced alcohol consumption during the study period, but this needs to be specifically addressed in a randomized controlled trial. Future research is needed to evaluate the engagement with and efficacy of InDEx for the reduction of alcohol consumption and binge drinking in an armed forces population.
Online supplement: Infographic representing the InDEx ecosystem.
List of alcohol types and categories included in the InDEx App.
alcohol use disorders identification test
behavior change technique
generalized anxiety disorder
Health Action Process Approach
Information about Drinking for Ex-serving
interquartile range
patient health questionnaire
short message service
This study was funded by the Medical Research Council (MR/N028244/2). We thank Margaret Jones of the King’s Centre for Military Health Research, King’s College London, for her assistance during the development of the InDEx app. The views expressed are those of the authors and do not necessarily reflect the views of the Department of Health, the National Institute for Health Research, Ministry of Defence or the Medical Research Council.
NTF is a member of the Independent Group Advising on the Release of Data for NHS (National Health Service) Digital and a trustee of The Warrior Programme. NJ is a serving member of the UK armed forces, but was not directed in any way by the Ministry of Defence. CD is partly funded by the National Institute for Health Research (NIHR) Biomedical Research Centre for Mental Health at South London and Maudsley NHS Foundation Trust and King’s College London and partly funded by the NIHR Collaborations for Leadership in Applied Health Research and Care South London at King’s College Hospital NHS Foundation Trust.