Study design and setting
This study is a prospective 6-month, single-arm mixed-methods pilot study designed to evaluate smoking cessation outcomes, acceptability, and psychological outcomes of the mHealth intervention nuumi. Data will be collected in Germany.
Participants
Interested individuals are screened for eligibility by completing a brief online questionnaire. Eligible participants are aged 18–65 years, report having smoked at least 5 cigarettes per day (CPD) for at least 12 months, are motivated to stop smoking (Motivation To Stop Scale (MTSS; [51]) > 4 points), have daily access to their own smartphone (iOS 15/Android 11 or more recent), reside in Germany, have access to a personal email account, and report being able to read and write in German.
Ineligibility criteria include self-reported current or planned pregnancy, breastfeeding, a self-reported allergy to vegetable glycerin or propylene glycol, drug and/or alcohol dependence, severe psychiatric or physical illness, a disease or medication associated with a contraindication to the use of EC, and medication that could affect the outcomes of the study (bupropion/ nortriptyline/ varenicline/ cytisine/ clonidine/ antidepressants). Exclusion criteria also include surgery (with anesthesia) in the last 6 weeks, participation in any other smoking cessation program, current use of EC/tobacco heaters/alternative tobacco products/NRT for more than 5 days during the last 30 days, and the inability to consent.
Recruitment
Recruitment started in the end of October 2023 via online advertisements, flyers, and a study website. A total of 70 participants will be recruited until recruitment is complete. Interested individuals can register on the study website and participate in a screening survey. Participants who are deemed eligible by study staff will be informed of their eligibility and receive the informed consent document. The document contains detailed information about the intervention, study procedures, potential risks and benefits of study participation, data handling and data protection. Consent can be given online by clicking on a “I consent” checkmark box. Upon submitting their informed consent form (Appendix B) electronically, participants will be emailed an electronic link to the baseline survey (t0). To prevent individuals from participating in the survey more than once, study staff will screen for duplicates of first and last names and email addresses during registration.
Incentives
Participants will receive 10€ for each completed survey (t1– t4). For participation in the semi-structured interviews, participants can earn another 10€ for each interview for a total incentive of 60€ once the study has ended.
Participant timeline
The study will be conducted over a six-month period, during which a total of five surveys will be administered and two interviews will be conducted with a subgroup of participants. Quantitative data collection will take place at t0, 4 weeks post-baseline (t1), 8 weeks post-baseline (t2), 12 weeks post-baseline (t3) and 24 weeks post-baseline (t4). All participants will receive access to the nuumi intervention directly after t0 data collection. Participants will be granted 2 weeks to complete each survey. Primary and secondary outcomes of this study will be answered by analyzing t3 and t4 data. To minimize fraud potential, survey invitations are personalized and can only be accessed with an individual access key. Surveys can only be completed once by using the individual access key.
Semi-structured interviews will be conducted by research staff with a sub-sample of 15 enrolled participants via videocall or telephone at t0 and t3. Participants are invited to partake in the baseline survey. Interested participants will indicate their willingness to be invited via email at the end of the baseline survey and will be sent an informed consent form to be signed electronically (Appendix B). The first interview will be conducted within 2 weeks after t0, and the second interview within 2 weeks after t3. In interview 1, participants will be asked about previous cessation attempts and perceived barriers to smoking cessation, their perceptions, and attitudes towards ECs and towards the use of smartphone apps for smoking cessation. In interview 2, participants will be interviewed about their current smoking and EC use status, their perceptions of the different intervention features, and the perceived effectiveness of the program. Participants may participate in both interviews, however, having participated in the first interview is not a prerequisite for participation in interview 2.
Participant flow and study design are outlined in Fig. 1 in an adapted Consolidated Standards for Reporting Trials (CONSORT-EHEALTH) diagram for pilot and feasibility trials [52, 53].
Participant flow and study design
Intervention
Nuumi is a self-guided digital therapeutic intervention comprising an app-based behavioral therapy and an EC connected to the app via Bluetooth. Initially, participants are asked to use the EC whenever they crave a cigarette, hence replacing cigarettes with the EC. In parallel, participants are prompted to use the app-based behavioral therapy providing information on transitioning to the EC, and smoking cessation. The app also contains information on gradual EC cessation, thus supporting the user in achieving abstinence of both products.
After completion of the baseline survey, participants receive instructions to download the app and will receive a voucher allowing them to order the EC and pods lasting for a minimum of 3 months from the manufacturer’s website at no cost. Participants are also issued a prepaid return label to return unused pods to the manufacturer in case they decide to stop using the EC and/or the program altogether.
Participants are not required to quit smoking immediately after baseline; they are advised to switch from combustible cigarettes to using the EC either by choosing a quit date, or by gradually switching from smoking to using EC over a 2-week period. The EC has been developed and manufactured by the funder of this study. It is a closed system device; i.e. empty pods cannot be refilled by the user and must instead be replaced with prefilled pods obtained through the manufacturer which can only be used after activation via the app.
Participants will receive a kit including the EC, a charger, a power bank, pods, and manuals for the EC and the pods via mail. Each participant will be supplied with an amount of pods equivalent to their respective cigarette consumption at study entry, estimated according to a guideline by the manufacturer. Participants can choose between two kinds of tobacco flavors when ordering the EC. The liquid solution in the pods includes propylene glycol, glycerol, nicotine, and flavoring. The EC is puff activated and the settings cannot be modified by the user. It is powered by a 450 mAh battery.
The participants receive pods in nicotine strength 20 mg/ml to 0 mg/ml, decreasing in steps of two mg/ml. Participants are prompted to start out with the 20 mg/ml pods and gradually use pods containing lower nicotine strength when one has been used up.
The EC is coupled with the nuumi app via Bluetooth, allowing for tracking of patterns of use, e.g. number of daily puffs (see Figure 2). These data are made visible to the user in the app. Two weeks after program start, users are presented a daily puff budget based on their average daily puffs previously recorded and are encouraged not to exceed the number of allotted puffs. Limiting the number of puffs serves the purpose of preventing compensatory puffing [54] when the nicotine concentration in the liquids is reduced. An app feature allows participants to reduce or increase their puff budgets as needed.
(1) Bluetooth-enabled nuumi EC, (2) app section Today depicting tracking of daily puffs, current nicotine strength, and tracked cigarettes, (3) app section Progress showing EC use statistics
To support participants in transitioning to the EC, and to subsequently reach abstinence from the EC, behavioral therapy is provided in the nuumi app which features evidence-based content informed by CBT-based and mindfulness-informed principles. Basis of the behavioral therapy is an initial in-person health promotion and stress management course certified by German statutory health insurance which features information from four core areas, including behavior, exercise, relaxation, and nutrition (BERN, [55, 56]). For the purpose of the present smoking intervention, the course has been digitalized, and its content has been modified to meet the needs of adults who smoke. The content is delivered via educational audio recordings, interactive exercises, and quizzes. The user is prompted to complete a total of 11 modules with each new module made accessible after the previous one has been completed (see Table 1 Appendix A and Fig. 3).
Examples of lessons within the therapy modules
Abbreviated versions of the coping techniques introduced in the modules are made accessible within the Toolbox section of the app; participants are advised to apply these coping techniques when dealing with cravings, stress, negative thoughts, and emotions (e.g. “urge surfing” [57]). In addition, the app features a meditation library with 32 guided meditation audios (see Fig. 4). The meditations, recorded by a professional meditation speaker, are split into 8 categories (relaxation, thoughts and feelings, sleep, body and movement, focus, communication, compassion and gratitude, happiness) and are accompanied by binaural beats [58].
App section Training consisting of (1) 11 therapy modules, and (2) a Library featuring a Toolbox and meditation audios
As a means of self-monitoring their cessation behavior, users can track the number of smoked combustible cigarettes in the app. Twelve puffs per cigarette are added to their daily EC puffs and depicted accordingly in the app. Additional nuumi app features include a dashboard that participants can use to track their current pod nicotine concentration, number of daily puffs, as well as progress on the behavioral therapy modules, and meditation minutes. Further, as a self-monitoring tool, users are prompted to answer one question concerning their smoking self-efficacy once per week within the app (“How confident are you that you will be completely abstinent from smoking cigarettes in one year from now?” not confident at all—very confident). Daily check-ins take place throughout the first 14 days of the nuumi program. During these check-ins, participants learn more about EC use and receive tips and motivational content to aid their transition from cigarettes to the EC. Users receive daily push notifications containing motivational and informative text messages based on the therapy modules. No substantial revisions to the app are planned during the trial period, and the anticipated app updates are limited to bug fixes.
The nuumi intervention was developed within the framework of Michaelsen and Esch’s Behavior Change Resource Model (BCRM) [28, 59]. The BCRM states that in the development of effective interventions for health behavior change, it is crucial to identify the resources necessary for successful behavior change and to select behavior change techniques (BCTs) most likely to support individuals in reaching their target behavior. Drawing upon a range of theories from social and health psychology, the behavior change process is commonly characterized as involving distinct stages (non-awareness, awareness, contemplation, planning, initiation, continued action, maintenance) that individuals traverse in pursuit of their goal [60]. At each of these stages, individuals require specific resources, defined as factors of an individual that can affect behavior, which can be categorized into three distinct sets, i.e. external, internal reflective, and internal affective resources which are characterized by both changeable and non-changeable factors [28, 59].
Internal resources are defined as bio-psychological resources pertaining to an individual’s internal state. Internal reflective resources are generated, accessed, or improved through effort and conscious deliberation, such as goals and behavioral regulation [28]. Internal affective resources, in contrast, can quickly be activated through stimuli without intentional effort, e.g. emotions and their reinforcement [28]. External resources refer to the socio-environmental resources that facilitate behavior change and can be provided, modified, or generated by the individual or others [28]. All these resources can be addressed by health BCTs, categorized into three groups: facilitating, boosting, and nudging [28, 59].
Facilitating BCTs provide external resources to facilitate new behavior, such as changes in the environment or material resources [28, 59]. The behavior change initiated through facilitating BCTs can, by definition, only last as long as the provision is sustained. However, through the provision of external resources, individuals may acquire a set of skills or routines to sustain the new behavior even when the external support is no longer available [28, 59]. A facilitation-based feature of the nuumi intervention is for example the provision of the EC as a material resource. By gaining access, individuals may acquire skills allowing them to navigate a situation in which they are offered a cigarette; once adopted, the skill can be applied even if the EC is no longer available [28, 59]. Boosting BCTs aim to strengthen internal reflective resources [28, 59]. By incorporating cognitive involvement of the individual, boosts foster competencies through changes in skills, knowledge, or decision-making competencies [61]. Boosting-based features included in the nuumi program are e.g. educational videos, audios and interactive exercises within the behavioral therapy part. Theoretically, the strengthening of said resources should generate persistent effects even after the intervention is removed, as competencies including dependence-related knowledge or mindfulness can remain stable over time [28, 59]. Lastly, nudging BCTs guide behavior by modifying choice architecture to a specific direction while maintaining freedom of choice [28, 59]. By intentionally applying stimuli, cues, or triggers in an environment, nudging engages affective decision-making elements, rendering the desired behavior more motivationally appealing and intrinsically rewarding [28, 59]. Nudging interventions do not rely on cognitive skills or the provision of external resources to be effective, but rather function through affective components of human motivation and reward processes [28, 59]. These interventions can lead to the formation of new routines without intentional effort from the individual, particularly when they are repeatedly applied [28, 59]. Nudging-based features of nuumi include, among others, the progress tracking dashboard, and daily push notifications containing motivational text messages.
Informed by the BCRM [28, 59], nuumi’s features make use of facilitating, boosting, and nudging techniques to produce behavior change among adults who smoke and are motivated to quit. BCTs were carefully selected and applied, tailoring nuumi to meet their specific needs.
Data collection, management, and monitoring
Data will be collected via a web-based data collection tool (LimeSurvey; LimeSurvey GmbH, Hamburg, Germany). Participants will receive a personalized link to the web-based survey via email and will receive up to two reminder mails within a period of two weeks prompting them to complete the surveys. Data from non-completers will be used to calculate the loss to follow-up rates. Participants will be allowed to skip any question they do not wish to answer. At the end of each web-based survey, the participants can enter feedback or additional comments into a text box.
The university is responsible for storing and protecting the research data. All data will be stored in electronic format on a secure university network location accessible only by authorized members of the research team. The data monitoring committee will comprise the university research team. During data collection, range checks for data values and additional steps to ensure data quality will be conducted by two research team members. Preliminary analyses are planned for t1, and t2 data after data collection of the respective time point is completed. Primary and secondary outcomes will be assessed with t3 and t4 data to address the aims of this study. Qualitative data from semi-structured interviews at t0 and t3 will be analyzed upon completion of all interviews.
App feature utilization data collected by Sanos Group GmbH is stored on a secured network location only accessible by employees of Sanos Group GmbH. Sanos Group GmbH receives the name and email address of the participants for the transmission of the app usage data to the research staff. The participants consent to this data exchange in the informed consent document.
Adverse events will be reported to the Institutional Review Board (IRB) and to the study funder. Documentation of such events will be stored on the university’s secure network location. Participants reporting severe adverse events or side effects from the EC use will be suggested to not use the EC further.
Outcomes
Outcome measures and other variables with their respective assessment time points are shown in Table 2 in Appendix A.
Sociodemographic variables
Sociodemographic variables will include age (in years), gender (male; female; diverse), highest level of education (no professional qualification; recognized professional training; bachelor’s degree or equivalent; master’s degree or equivalent; doctorate), employment status (student; employed full-time; employed part-time; employed on a marginal basis (no more than 520€/month); unemployed; retirement pension; disability pension; homemaker; educational retraining; reintegration program; other), household income (in EUR), marital/relationship status (in a partnership living together; in a partnership not living together; single, divorced or separated; widowed), number of children. In addition, participant characteristics will include height (in cm), weight (in kg), pregnancy, previous meditation experience (yes or no), and openness to meditation (yes or no).
Primary and secondary outcomes
Primary outcome
The primary outcome will be self-reported 7-day point prevalence abstinence from smoking (PPA) at t3 and t4, operationalized as not having smoked any cigarettes, not even a single puff, in the last 7 days [62].
Secondary outcomes
Smoking cessation related secondary outcomes at t3 and t4 will include percentage reduction in CPD, 30-days PPA, repeated PPA, continuous PPA (< 5 cigarettes since target quit date), and urges to smoke (VRS v4-1) [63]. Other secondary outcomes will include perceived stress (Perceived Stress Scale; PSS-10) [64], mindfulness (Freiburg Mindfulness Inventory short version; FFA) [65], smoking self-efficacy (“How confident are you that you will be completely abstinent from smoking cigarettes in one year from now? (1 “not confident at all” -10 “very confident”), and Smoking Self-Efficacy Questionnaire; SEQ-12) [66], subjective health (Short Form Health Survey; SF-12) [67], and life satisfaction (L-1) [68].
The acceptability of the nuumi program will be operationalized as (1) usefulness in quitting smoking (“How helpful do you find the program in not smoking cigarettes?”, “To what extent does the program increase your confidence to quit smoking?”), (2) satisfaction with the program (“How would you rate your overall satisfaction with the smoking cessation program?”https://ascpjournal.biomedcentral.com/”How likely are you to recommend the program to friends or colleagues who want to quit smoking?”), (3) comprehensibility of the content (“How informative did you find the content of the behavioral training?” / “How understandable did you find the content of the behavioral training?”). Usability of the app is also assessed using the System Usability Scale (SUS) [69].
For each questionnaire, the validated German version will be used. If no German version is available, translations will be made by the study staff.
Other variables
Smoking behavior-related variables
Smoking behavior-related variables include years of smoking, motivation to quit (Motivation To Stop Scale) [70], number and method(s) of previous quit attempts, use of alternative tobacco products and/or ECs, current participation in other smoking cessation program, current use of NRT, and withdrawal symptoms (Wisconsin Smoking Withdrawal Scale; WSWS2-B) [71]. Additionally, EC dependence is queried (Penn State Electronic Cigarette Dependence Index; PSECDI) [72].
Adherence and engagement
Adherence is operationalized as (1) self-reported use of the EC (current use and number of days of use), and (2) self-reported engagement with the app (number of daily/weekly uses, number of modules completed, minutes meditated). Participants will be asked whether they participate in any other smoking cessation program in each survey from t0 onwards.
Subjective evaluation and side effects
Subjective evaluation of the EC and side effects will be measured using items from a variety of scales assessing subjective effects of ECs [12]. Participants will be asked about adverse events in each survey from t1 onwards and requested to report all adverse events occurring between the survey time points to the study staff.
Nuumi program feature utilization
In addition to the self-reported EC and app utilization data, app feature utilization data of the nuumi program will be collected by the manufacturer of nuumi, Sanos Group GmbH, for the first 8 weeks after program initiation. Using this data, separate secondary analyses will be conducted to investigate the degree to which users engaged with the individual program features, and the relationships between utilization of individual features and smoking abstinence at 4 weeks and 8 weeks post-baseline. Utilization metrics collected by Sanos Group GmbH will include (1) the number of behavioral therapy lessons completed, (2) the number of meditations completed and/or repeated, (3) the number of toolbox exercises completed, (4) the number of times the progress tracking feature was accessed, and (5) the number of days the EC was used.
Sample size
Formal sample size calculations are not required for single-arm pilot studies [73]. Target sample size estimation is based on single-arm pilot studies evaluating interventions for smoking cessation [74,75,76]. In order to address the primary and secondary aims of this trial, and to account for attrition, the target sample size is 70 participants.
Statistical methods
Quantitative data analyses
Analyses will be conducted using the statistical software R, version 4.4.0 (R Core Team, 2024). Given the exploratory nature of this study, data analyses will primarily be descriptive. For categorical variables, frequencies and percentages will be reported. For continuous variables, mean and standard deviation (SD) will be reported. If applicable, statistical comparisons for paired data will be applied to compare scores observed before and after program participation. Statistical significance will be evaluated using a repeated measures two-tailed t-test; the alpha level will be set at 0.05 and a 95% confidence interval will be used. Intention-to-treat (ITT) analyses will be conducted, assuming all individuals not completing a follow-up survey have resumed smoking. In addition, complete cases will be analyzed, i.e. only participants completing the t3 and t4 survey, respectively, will be included in these analyses. Percentages and patterns of missing data will be assessed using Little’s Missing Completely At Random test and adequate data imputation techniques will be used, if applicable.
Primary and secondary outcomes
For the primary outcome, 7-day PPA at t3 and t4, number and percentage of participants self-reporting abstinence will be reported. For the secondary outcomes, measures of frequency and percentages will be reported for 30-days PPA, repeated PPA and continuous PPA, and measures of central tendency will be reported for CPD and urges to smoke. Paired t-tests will be conducted to assess changes in CPD and urges to smoke from t0 to t3 and from t0 to t4. Mean and SD will be reported for perceived stress, mindfulness, smoking self-efficacy, subjective health and life satisfaction, and paired t-tests will be conducted to assess within-subject changes in these variables. Acceptability outcomes will be reported descriptively.
Participant characteristics
Frequency measures and percentages will be reported for categorical variables (gender, education, occupational status, household income, relationship status, previous meditation experience, openness to meditation). For continuous variables (age, number of children, height, weight), mean and SD will be reported. Changes in weight will be calculated using paired t-tests. In addition, it will be investigated how demographic characteristics of the participants are associated with the collected outcomes using bivariate tests, including Pearson’s r correlations.
Other variables
Frequency measures and percentages will be reported for method(s) of previous quit attempts, use of alternative tobacco products and ECs, participation in other smoking cessation programs, NRT use, and EC dependence. Mean and SD will be calculated for years of smoking, motivation to quit, number of previous quit attempts, and withdrawal symptoms. To assess adherence and engagement, frequencies and percentages of current EC use, and number of days of use will be reported. Mean and SD for engagement with the app will be calculated. Further, frequencies and percentages will be reported for the subjective evaluation of the EC, side effects, and adverse events.
Nuumi program feature utilization
As indicators for feature utilization, we will analyze a set of variables including (1) the number of completed behavioral therapy lessons, (2) the number of meditation audios completed and/or repeated, (3) the number of toolbox exercises completed and/or repeated, (4) the number of times the progress tracking feature was accessed, and (5) the number of days the nuumi EC was used. A total engagement score will be calculated across all intervention components. For each of the five utilization variables, a median split will be conducted, each resulting in two categories of 0 (“below median utilization”) and 1 (“above median utilization”). The five scores will be added, resulting in a single score (ranging from 0 to 5). Two logistic regressions will be performed with total program engagement as the predictor variables and 7-day PPA from smoking at 4-weeks and 8-weeks post-baseline as the dependent variables (with 0 indicating “non-abstinent” and 1 indicating “abstinent”). To examine the relationship between feature utilization and smoking cessation, a total of 10 univariate logistic regressions for each of the five features will be performed to predict 7-day PPA from smoking at 4-weeks and 8-weeks post-baseline. The predictor variable will be the respective app feature utilization, and 7-day PPA will be the dependent variable.
To control for confounding effects on the relationship between feature utilization and smoking cessation outcomes, we will control for baseline characteristics that significantly differed by smoking status at t1, or t2, or both. To identify these variables, independent samples t-tests will be conducted for continuous variables, and chi-square tests for categorical variables.
Qualitative data analyses
The 1:1 semi-structured interviews will be conducted by research staff, recorded via Zoom and transcribed verbatim. Interview guidelines were developed to ensure all relevant information to answer the research questions is collected and comparability between interviews is guaranteed. The recordings will be analyzed using qualitative content analysis [77]. The primary analysis will be carried out by HS and CH using MAXQDA (Verbi GmbH, Berlin, Germany). After reading and re-reading the transcripts, the content will be split into meaningful categories. An initial coding scheme will be developed individually by HS and CH by assigning codes to the categories based on similarities. Codes will be compared, and discrepancies will be discussed between HS and CH until consensus is achieved. While applying the agreed coding scheme, HS and CH will repeatedly check for consistency by independently coding some same segments of text and then comparing results. Overarching themes that emerge from the identified categories will be identified and quotes from the interviews illustrating each theme will be selected.
Anonymized transcripts of the audio recordings will be stored in a secure university network location accessible only by authorized members of the research team. Once the audio recordings have been transcribed, the audio recordings will be deleted.
Ethical considerations
Research ethics approval
Ethics approval was obtained from the Institutional Review Board (IRB) in September 2023 (123/2023). Any amendments will be submitted to the IRB, to the study funder, to the German Clinical Trial Registry, and to the journal where this manuscript was submitted.
Confidentiality and access to data
Personal information about potential and enrolled participants will be collected only by members of the research team and cannot be accessed by other individuals. Personal information and survey data will be pseudonymized using an identification number. Only authorized study staff will have access to any of the study data. Participant files will be stored for a period of 10 years after completion of the study in anonymized format.
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