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There are no known efficacious digital smoking cessation interventions for Hispanic/Latinx adults who smoke. This study is a secondary analysis using data from a randomized trial to evaluate whether Acceptance and Commitment Therapy (ACT) delivered via a smartphone app (iCanQuit) would be more efficacious for smoking cessation than the US Clinical Practice (USCPG)-based app (QuitGuide) in a sample of Hispanic/Latinx participants. A total of 210 Hispanic/Latinx adults who smoke were randomized to receive the iCanQuit or QuitGuide app for 12-months. Participants self-reported on 30-day abstinence from cigarette smoking at the 3-month, 6-month, and 12-month follow-ups; 7-day abstinence at all follow-ups; abstinence from other nicotine/tobacco products at 12-months; and continuous prolonged abstinence from 3 to 12-months. Participants also reported on their willingness to accept cues to smoke without smoking and satisfaction with their apps. A total of 176 (84%) participants reported on study outcomes at the 12-month follow-up. Compared to QuitGuide participants, iCanQuit participants were significantly more likely to report 30-day abstinence from cigarette smoking at 12-months (34% iCanQuit, 20% QuitGuide; p = 0.026). iCanQuit participants utilized their app more frequently and reported greater satisfaction with their assigned app than those who received the QuitGuide app. Increases in participants' willingness to accept cues to smoke mediated the intervention effect on abstinence from cigarette smoking at 12-months. Acceptance and Commitment Therapy-delivered via a smartphone app may be efficacious for helping Hispanic/Latinx adults abstain from cigarette smoking. Replication in a fully powered randomized trial that focuses on an independent sample of Hispanic/Latinx adults is now needed. • Smartphone interventions can help Hispanic/Latinx adults quit smoking. • iCanQuit yielded greater abstinence of cigarette smoking than QuitGuide. • iCanQuit was more utilized and highly rated compared to QuitGuide. [ABSTRACT FROM AUTHOR]

Objective: Anxiety symptoms are common among cancer survivors. This study evaluated whether an acceptance-based group intervention delivered by social workers in community oncology clinics improved anxiety and related symptoms, and healthcare use, relative to enhanced usual care (EUC). Method: This multi-site trial included 135 survivors of various cancers with moderate to high anxiety about cancer/survivorship, 1.5–24 months after treatment. Participants were randomized 1:1 to a 7-session acceptance and commitment therapy (ACT)-based group (Valued Living) or EUC (access to onsite supportive care plus resource list). Questionnaires were administered at baseline, 1, 2, 5, and 8 months post-randomization, diagnostic interviews at baseline, 2, and 8 months, and healthcare use tracked throughout. Outcomes included anxiety symptoms (primary), related symptoms, and healthcare use. Putative moderators included age, anxiety, and avoidance. Results: In intent-to-treat comparisons to EUC, Valued Living (VL) showed a nonsignificant pattern of greater improvement on anxiety symptoms (p =.08), improved significantly more on cancer-related post-traumatic stress (p =.002), fear of recurrence (p =.003), and energy/fatigue (p =.02), and missed significantly fewer medical appointments (p <.05). Conditions improved similarly on depressive symptoms, sense of meaning, and most severe anxiety or depressive disorder. Effects were moderated: VL participants with higher baseline anxiety or avoidance (+1SD) improved more on anxiety, meaning (ps ≤.01), and disorder severity (p =.05) than their EUC counterparts. Conclusions: An acceptance-based group intervention delivered in community oncology clinics enhanced psychological recovery and energy levels, and reduced missed medical appointments for anxious cancer survivors, with stronger effects for more distressed participants. Public Health Significance: This trial demonstrated that an acceptance and commitment therapy (ACT)-based group intervention for anxious cancer survivors, as delivered by clinical social workers in community cancer care clinics, accelerated psychological recovery and energy levels, and reduced missed medical appointments. The effects were stronger and broader for more anxious and avoidant participants, demonstrating that cancer survivors with more pronounced psychological symptoms benefitted most. [ABSTRACT FROM AUTHOR]

Throughout its history the strategy and tactics of contextual behavioral science (CBS) research have had distinctive features as compared to traditional behavioral science approaches. Continued progress in CBS research can be facilitated by greater clarity about how its strategy and tactics can be brought to bear on current challenges. The present white paper is the result of a 2 1/2-year long process designed to foster consensus among representative producers and consumers of CBS research about the best strategic pathway forward. The Task Force agreed that CBS research should be multilevel, process-based, multidimensional, prosocial, and pragmatic, and provided 33 recommendations to the CBS community arranged across these characteristics. In effect, this report provides a detailed research agenda designed to maximize the impact of CBS as a field. Scientists and practitioners are encouraged to mount this ambitious agenda. • The strategies and tactics of contextual behavioral science research are distinctive. • CBS research is multilevel, process-based, multidimensional, prosocial, and pragmatic. • Targeted research is needed in all five of these areas. • Thirty-three recommendations are offered to direct and improve CBS research. • These recommendations can be used as a quality improvement checklist. [ABSTRACT FROM AUTHOR]

Objective: To examine whether military separation (Veteran), service component (active duty, Reserve/National Guard), and combat deployment are prospectively associated with continuing unhealthy alcohol use among US military service members. Methods: Millennium Cohort Study participants were evaluated for continued or chronic unhealthy alcohol use, defined by screening positive at baseline and the next consecutive follow-up survey for heavy episodic, heavy weekly, or problem drinking. Participants meeting criteria for chronic unhealthy alcohol usewere followedforup to 12 years to determine continued unhealthy use. Multivariable regression models--adjusted for demographics, military service factors, and behavioral and mental health characteristics--assessedwhether separation status, service component, or combat deployment were associated with continuation of 3 unhealthy drinking outcomes: heavy weekly (sample n¼2653), heavy episodic (sample n¼22,933), and problem drinking (sample n¼2671). Results: In adjusted models, Veterans (compared with actively serving personnel) and Reserve/Guard (compared with active duty members) had a significantly higher likelihood of continued chronic use for heavy weekly, heavy episodic, and problem drinking (Veteran odds ratio [OR] range 1.17--1.47; Reserve/Guard OR range 1.25-- 1.29). Deployers without combat experience were less likely than nondeployers to continue heavy weekly drinking (OR 0.75, 95% confidence interval 0.61--0.91). Conclusions: The elevated likelihood of continued unhealthy alcohol use among Veterans and Reserve/Guard members suggests that strategies to reduce unhealthy drinking targeted to these populations may be warranted. [ABSTRACT FROM AUTHOR]

Limb salvage surgery has become a first-line treatment in the setting of lower extremity cancer. Despite a multitude of techniques, the most effective modality for osseous reconstruction has not been described. We aim to examine outcomes of allograft reconstruction alone compared to an allograft combined with a vascularized fibula graft (VFG) (Capanna Technique) through a meta-analysis of the literature. A systematic review of the literature was conducted through the online databases PubMed, Embase, and Web of Science, examining articles utilizing an allograft with or without an intramedullary VFG for the reconstruction of lower extremity osseous defects following oncological resection. A meta-analysis examined outcomes, including nonunion, infection, fractures, explantation, and functional limb status, that were evaluated dependent upon reconstructive modality. Twenty-five articles were deemed appropriate for inclusion. The allograft with VFG group had considerably lower rates of nonunion (13%) in comparison to the allograft alone group (21.4%) (p <.001). Rates of infection (7.9% vs. 9%, respectively) and fracture (19.6% vs. 19.1%) were not statistically different. The allograft with VFG group also had significantly lower rates of explantation (6.57%) compared to the allograft alone cohort (18.11%) (p <.001). Functional outcomes were similar across groups as measured by Musculoskeletal Tumor Society scores (88.22% vs. 87.77%). Allograft reconstruction with a supplementary inlay VFG decreases the risk of nonunion and explantation compared to allograft alone reconstruction in the setting of oncological resection of the osseous lower extremity. This technique warrants increased consideration in the operative planning of lower limb reconstruction following tumor extirpation. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to determine whether specific individual posttraumatic stress disorder (PTSD) symptoms or symptom clusters predict cigarette smoking initiation. Methods: Longitudinal data from the Millennium Cohort Study were used to estimate the relative risk for smoking initiation associated with PTSD symptoms among 2 groups: (1) all individuals who initially indicated they were nonsmokers (n=44,968, main sample) and (2) a subset of the main sample who screened positive for PTSD (n=1622). Participants were military service members who completed triennial comprehensive surveys that included assessments of smoking and PTSD symptoms. Complementary log-log models were fit to estimate the relative risk for subsequent smoking initiation associated with each of the 17 symptoms that comprise the PTSD Checklist and 5 symptom clusters. Models were adjusted for demographics, military factors, comorbid conditions, and other PTSD symptoms or clusters. Results: In the main sample, no individual symptoms or clusters predicted smoking initiation. However, in the subset with PTSD, the symptoms "feeling irritable or having angry outbursts" (relative risk [RR] 1.41, 95% confidence interval [CI] 1.13-1.76) and "feeling as though your future will somehow be cut short" (RR 1.19, 95% CI 1.02-1.40) were associated with increased risk for subsequent smoking initiation. Conclusions: Certain PTSD symptoms were associated with higher risk for smoking initiation among current and former service members with PTSD. These results may help identify individuals who might benefit from more intensive smoking prevention efforts included with PTSD treatment. [ABSTRACT FROM AUTHOR]

Objectives: Posttraumatic stress disorder (PTSD) and unhealthy alcohol use are commonly associated conditions. It is unknown whether specific symptoms of PTSD are associated with subsequent initiation of unhealthy alcohol use. Methods: Data from the first 3 enrollment panels (n=151,567) of the longitudinal Millennium Cohort Study of military personnel were analyzed (2001-2012). Complementary log-log models were fit to estimate whether specific PTSD symptoms and symptom clusters were associated with subsequent initiation of 2 domains of unhealthy alcohol use: risky and problem drinking (experience of 1 or more alcohol-related consequences). Models were adjusted for other PTSD symptoms and demographic, service, and health-related characteristics. Results: Eligible study populations included those without risky (n=31,026) and problem drinking (n=67,087) at baseline. In adjusted analyses, only 1 PTSD symptom--irritability/anger--was associated with subsequent increased initiation of risky drinking (relative risk [RR] 1.05, 95% confidence interval [CI] 1.00-1.09) at least 3 years later. Two symptom clusters (dysphoric arousal [RR 1.17, 95% CI 1.11-1.23] and emotional numbing [RR 1.30, 95% CI 1.22-1.40]) and 5 symptoms (restricted affect [RR 1.13, 95% CI 1.08-1.19], sense of foreshortened future [RR 1.12, 95% CI 1.06-1.18], exaggerated startle response [RR 1.07, 95% CI 1.01-1.13], sleep disturbance [RR 1.11, 95% CI 1.07-1.15], and irritability/ anger [RR 1.12, 95% CI 1.07-1.17]) were associated with subsequent initiation of problem drinking. Conclusions: Findings suggest that specific PTSD symptoms and symptom clusters are associated with subsequent initiation of unhealthy alcohol use. Key Words: military, posttraumatic stress disorder, unhealthy alcohol use [ABSTRACT FROM AUTHOR]

Background: Little is known about how individuals engage over time with smartphone app interventions and whether this engagement predicts health outcomes.Objective: In the context of a randomized trial comparing 2 smartphone apps for smoking cessation, this study aimed to determine distinct groups of smartphone app log-in trajectories over a 6-month period, their association with smoking cessation outcomes at 12 months, and baseline user characteristics that predict data-driven trajectory group membership.Methods: Functional clustering of 182 consecutive days of smoothed log-in data from both arms of a large (N=2415) randomized trial of 2 smartphone apps for smoking cessation (iCanQuit and QuitGuide) was used to identify distinct trajectory groups. Logistic regression was used to determine the association of group membership with the primary outcome of 30-day point prevalence of smoking abstinence at 12 months. Finally, the baseline characteristics associated with group membership were examined using logistic and multinomial logistic regression. The analyses were conducted separately for each app.Results: For iCanQuit, participants were clustered into 3 groups: "1-week users" (610/1069, 57.06%), "4-week users" (303/1069, 28.34%), and "26-week users" (156/1069, 14.59%). For smoking cessation rates at the 12-month follow-up, compared with 1-week users, 4-week users had 50% higher odds of cessation (30% vs 23%; odds ratio [OR] 1.50, 95% CI 1.05-2.14; P=.03), whereas 26-week users had 397% higher odds (56% vs 23%; OR 4.97, 95% CI 3.31-7.52; P<.001). For QuitGuide, participants were clustered into 2 groups: "1-week users" (695/1064, 65.32%) and "3-week users" (369/1064, 34.68%). The difference in the odds of being abstinent at 12 months for 3-week users versus 1-week users was minimal (23% vs 21%; OR 1.16, 95% CI 0.84-1.62; P=.37). Different baseline characteristics predicted the trajectory group membership for each app.Conclusions: Patterns of 1-, 3-, and 4-week smartphone app use for smoking cessation may be common in how people engage in digital health interventions. There were significantly higher odds of quitting smoking among 4-week users and especially among 26-week users of the iCanQuit app. To improve study outcomes, strategies for detecting users who disengage early from these interventions (1-week users) and proactively offering them a more intensive intervention could be fruitful. [ABSTRACT FROM AUTHOR]

Abstract: Mobile technologies are growing rapidly around the world to broad demographics of society. These technologies hold great promise for their integration with Single Case Designs (SCDs) and the study of individuals in their natural environment. This paper discusses the theoretical, methodological and analytic implications of these tools for the advancement of the contextual behavioral etiology of behavioral disorders, and their remediation. We hope this paper will highlight the scientific advantages of combining mobile technologies and SCDs and encourage their adoption among CBS scientists. [Copyright &y& Elsevier]

Objective: This study investigated to what extent the prospective relationship between parental smoking cessation and child daily smoking is mediated by child cognitions about smoking. Design: The study drew its sample from the 40 Washington State school districts involved in the Hutchinson Smoking Prevention Project. The predictor variable of parental smoking cessation was measured during third grade. The mediator measures, consistent with the Theory of Planned Behavior and Social Cognitive Theory, were measured during ninth grade, and the smoking status outcome was measured during twelfth grade. Main Outcome Measures: Smoking status at twelfth grade. Results: Negative general attitudes toward smoking, attitude that cigarette smoke is bothersome, and tobacco refusal self-efficacy together significantly mediated 49% of the prospective relationship between parental smoking cessation and child daily smoking. Conclusion: Parental smoking cessation before children reach third grade may lead children to develop more negative cognitions about smoking, and. in turn, reduce their risk of smoking. [ABSTRACT FROM AUTHOR]

Objective: A 10-year follow-up study to test the extent to which theory-based adolescent psychological and social factors directly predict and moderate the prediction of young adult smoking acquisition and cessation. Design: A prospective community-based sample. A total of 2,970 adolescents participated in the large Washington State Hutchinson Smoking Prevention Project (HSPP) longitudinal cohort. As predictors, psychological factors (i.e., parentnoncompliance, friendcompliance, rebelliousness, achievement motivation, and thrill seeking) and social environmental factors (i.e.. parent's and friend's smoking) were measured when adolescents were 17-18 years old. Main Outcome Measures: As main outcome measures, smoking acquisition and cessation were assessed both at ages 18 and 28. Results: Psychological and social factors predicted 3% to 7% probability (p < .05) of smoking acquisition and a nonsignificant to 24% probability (p < .05) of smoking continuation (not quitting) in young adulthood. Both friendcompliance and rebelliousness were more powerful predictors of young adult-smoking continuation than of smoking acquisition. Conclusion: First evidence that parent noncompliance, friend compliance, and a lack of achievement motivation predict smoking acquisition and (with the exception of parent noncompliance) smoking continuation in young adulthood. Including these psychological factors in future interventions designed to promote young adult smoking cessation may be useful. [ABSTRACT FROM AUTHOR]

The article presents a randomized trial which examines whether social cognitive theory processes have mediated a large adolescent smoking cessation intervention trial's outcomes. The study shows that 55.6% of the intervention's effect on smoking cessation was statistically mediated by the increased self-efficacy to resist smoking in social and stressful situations. It indicates that self-efficacy to resist smoking is a possible mediator of the intervention's effect on smoking cessation.

The article presents a study on the feasibility and effectiveness of Acceptance and Commitment Therapy (ACT) in comparison with cognitive behavioral therapy (CBT) for smoking cessation. It notes that the ACT intervention condition used metaphors and experiential exercises to motivate quitting smoking and enhance willingness to experience urges and abstinence-related internal distress. Results show the feasibility of ACT treatment and demonstrate promising evidence of its effectiveness.

Objective: This study longitudinally investigated psychological and social risk factors consistent with the Theory of Triadic Influence (TTI) as predictors of adolescent smoking transitions. Design: Among 4218 adolescents, five psychological risk factors (i.e., parent-noncompliance, friend-compliance, rebelliousness, low achievement motivation, and thrill seeking) were assessed in 9th grade (age 14), two social influence risk factors (i.e., parents' and close friends' smoking) were assessed in Grades 3 (age 8) and 9 (age 14), respectively. Main Outcome Measures: Adolescent smoking transitions occurring between the 9th and 12th (ages 14-17) grade interval. Results: The probabilities contributed by each of the five psychological risk factors to the overall probability of making a specific smoking transition were: 22% to 27% for the transition from never to trying smoking, 10% to 13% for the transition from trying to monthly smoking, and, for three of the five risk factors, 11% to 16% for the transition from monthly to daily smoking. For predicting trying smoking, the probability contributed by these psychological factors was greater than the probability contributed by each parent's and close friend's smoking. Parent-compliance had a higher contribution to the probability of trying smoking when an adolescent's parent smoked (p < .05), whereas friend-compliance had a higher contribution to the probability of trying smoking when an adolescent's friend smoked (p < .001). Conclusion: These psychological and social factors have an important influence on adolescent smoking transitions. Implications for TTI and smoking prevention interventions are discussed. [ABSTRACT FROM AUTHOR]

To learn who experiences air travel stress, this study examined hypothesized demographic differences in the three components of the Air Travel Stress Scale: Air Travel Anxiety, Air Travel Anger, and Airline/Airport Trust. In two samples (N= 925; N = 2382) of air travelers, results showed that statistically significant indicators of higher Air Travel Anxiety were being a woman, being under age 54, having a gross annual household income of less than $60,000 US dollars, being a leisure traveler, and having eight or fewer domestic roundtrip flights in the past year. Indicators of higher Air Travel Anger were being a man, having a gross annual household income of at least $60,000, and being an international traveler. Finally, indicators of lower Airline/Airport Trust were being a man, being age 54 or younger, an income of at least $60,000, being a business traveler, and being an international traveler. Implications for understanding and intervening on air travel stress are discussed. [ABSTRACT FROM AUTHOR]

: PurposeTo explore the hypothesis that older siblings’ smoking, after controlling for parents’ smoking, influences children’s smoking.: MethodsStudy participants were 2981 students in the control cohort of a school-based smoking prevention randomized trial for whom parents’ smoking and older siblings’ smoking data were collected at 3rd grade and daily smoking data was assessed 9 years later through a self-report questionnaire at the 12th grade. Data were analyzed using conditional logistic regression and likelihood ratio tests.: ResultsFor families in which no parent smoked, the 12th grade prevalence of daily smoking was 31% when at least one older sibling smoked compared to 18% when no older sibling smoked. For families in which at least one parent smoked, the 12th grade prevalence of daily smoking was 41% when at least one older sibling smoked compared to 29% when no older sibling smoked. There was a substantial increase in the odds (OR = 1.60, p = .004) of children’s daily smoking at 12th grade when their older siblings smoked, even after adjusting for parents’ smoking.: ConclusionsOlder siblings’ smoking is associated with increased risk of children’s smoking after adjusting for parents smoking. Furthermore, there was no evidence to suggest that the influence of older siblings’ smoking was different in families where no parent smoked compared to those where at least one parent smoked. Also, there was no evidence that the influence of older siblings’ smoking was different in boys vs. girls. [Copyright &y& Elsevier]

Background: Web-based cessation programs are now common for intervening with smokers. However, it remains unclear how acceptable or effective these interventions are among people with affective disorders and symptoms (ADS; eg, depression and anxiety). Research examining this is extremely limited, with mixed results on cessation rates. Additional large studies are needed to more fully understand whether Web-based interventions are similarly used and equally effective among people with and without affective disorder symptomology. If not, more targeted Web-based interventions may be required.Objective: The goal of the research was to compare Web-based treatment acceptability (defined by satisfaction and use) and 12-month cessation outcomes between smokers with and without ADS.Methods: Participants (N=2512) were adult smokers enrolled in a randomized, comparative effectiveness trial of two Web-based smoking interventions designed for the general population of smokers. At baseline, participants reported demographic and smoking characteristics and completed measures assessing ADS. Participants were then classified into subgroups based on their self-reported ADS-either into a no ADS group or into six nonmutually exclusive subgroups: depression, posttraumatic stress disorder (PTSD), panic disorder (PD), generalized anxiety disorder (GAD), social anxiety disorder (SAD), and more than one ADS. Surveys at 12 months postrandomization included subjective ratings of treatment acceptability and self-reported smoking cessation. Treatment use (ie, number of log-ins and total duration of exposure) was assessed via automated records.Results: Relative to the no ADS group, all six ADS subgroups reported significantly greater satisfaction with their assigned Web treatment program, but they spent less time logged in than those with no ADS. For number of log-ins, a treatment arm by ADS group interaction was observed across all ADS subgroups except GAD, suggesting that relative to the no ADS group, they logged in less to one website but not the other. At the 12-month follow-up, abstinence rates in the no ADS group (153/520, 29.42%) were significantly higher than for participants who screened positive for depression (306/1267, 24.15%; P=.03), PTSD (294/1215, 24.19%; P=.03), PD (229/1003, 23.83%; P=.009), and two or more ADS (323/1332, 24.25%; P=.03). Post hoc analyses suggest the lower quit rates may be associated with differences in baseline nicotine dependence and levels of commitment to resist smoking in difficult situations. Website use did not explain the differential abstinence rates.Conclusions: Despite reporting higher levels of treatment satisfaction, most smokers with ADS used their assigned intervention less often and had lower quit rates than smokers with no ADS at treatment onset. The results support the need for developing more targeted interventions for smokers with ADS.Trial Registration: Clinical Trials.gov NCT01812278; https://clinicaltrials.gov/ct2/show/NCT01812278 (Archived by WebCite at http://www.webcitation.org/78L9cNdG4). [ABSTRACT FROM AUTHOR]

Background: Despite having many advantages, online eHealth trials are not without challenges-notably, participant recruitment, and outcome data retention. Moreover, publications from these trials rarely provide detailed information on the methods used for recruitment and retention or discuss implications of the methods for future studies.Objective: To address this need for empirical guidance regarding recruitment and outcome data retention planning, we aim to describe the methods and lessons learned from the recruitment and retention procedures used in a large randomized trial of 2 Web-based smoking cessation interventions.Methods: To ensure a demographically and geographically diverse participant sample, we used the recruitment strategies (1) traditional, (2) Web-based, and (3) online survey panel methods and adaptively modified each in response to recruitment success. At baseline, participants indicated how they heard about the study and answered demographic questions. To maximize trial retention at each of the 3-, 6-, and 12-month assessment points, 4 survey modalities (first Web, followed by phone, mail, and postcard) were sequentially timed over a 30-day period. Participants received US $25 for submitting their responses, regardless of modality, and received an additional US $10 bonus for completing the Web survey within 24h of electronic notification.Results: We randomized 2637 smokers in 16 months and achieved 88% retention at 12-months. Participants (79.26% female, 72.60% Caucasian) were recruited from all 50 states. The majority of participants were recruited through Facebook (49.43%), followed by the survey panel (20.85%), free internet sources (14.54%), traditional media (11.34%), and Google ads (3.84%). Descriptively, participant demographics varied by recruitment source. Of the completed follow-up surveys, most were completed by Web (92%). Retention rates did not vary by recruitment source.Conclusions: Continuous monitoring and refinement of multiple recruitment methods, particularly of online advertising campaigns, allowed us to maximize the effectiveness of recruitment strategies in recruiting a large, diverse sample of smokers. Likewise, offering multiple follow-up survey modalities in sequential order along with time-dependent bonus incentives enabled us to obtain outcome data from a very high level of enrolled participants for the duration of the trial protocol. These strategies may be similarly useful in other trials.Trial Registration: ClinicalTrials.gov NCT01812278; https://clinicaltrials.gov/ct2/show/NCT01812278 (Archived by WebCite at http://www.webcitation.org/71gy5GLvO). [ABSTRACT FROM AUTHOR]

Background: Little is known about how individuals engage with electronic health (eHealth) interventions over time and whether this engagement predicts health outcomes.Objective: The objectives of this study, by using the example of a specific type of eHealth intervention (ie, websites for smoking cessation), were to determine (1) distinct groups of log-in trajectories over a 12-month period, (2) their association with smoking cessation, and (3) baseline user characteristics that predict trajectory group membership.Methods: We conducted a functional clustering analysis of 365 consecutive days of log-in data from both arms of a large (N=2637) randomized trial of 2 website interventions for smoking cessation (WebQuit and Smokefree), with a primary outcome of 30-day point prevalence smoking abstinence at 12 months. We conducted analyses for each website separately.Results: A total of 3 distinct trajectory groups emerged for each website. For WebQuit, participants were clustered into 3 groups: 1-week users (682/1240, 55.00% of the sample), 5-week users (399/1240, 32.18%), and 52-week users (159/1240, 12.82%). Compared with the 1-week users, the 5- and 52-week users had 57% higher odds (odds ratio [OR] 1.57, 95% CI 1.13-2.17; P=.007) and 124% higher odds (OR 2.24, 95% CI 1.45-3.43; P<.001), respectively, of being abstinent at 12 months. Smokefree users were clustered into 3 groups: 1-week users (645/1309, 49.27% of the sample), 4-week users (395/1309, 30.18%), and 5-week users (269/1309, 20.55%). Compared with the 1-week users, 5-week users (but not 4-week users; P=.99) had 48% higher odds (OR 1.48, 95% CI 1.05-2.07; P=.02) of being abstinent at 12 months. In general, the WebQuit intervention had a greater number of weekly log-ins within each of the 3 trajectory groups as compared with those of the Smokefree intervention. Baseline characteristics associated with trajectory group membership varied between websites.Conclusions: Patterns of 1-, 4-, and 5-week usage of websites may be common for how people engage in eHealth interventions. The 5-week usage of either website, and 52-week usage only of WebQuit, predicted a higher odds of quitting smoking. Strategies to increase eHealth intervention engagement for 4 more weeks (ie, from 1 week to 5 weeks) could be highly cost effective.Trial Registration: ClinicalTrials.gov NCT01812278; https://www.clinicaltrials.gov/ct2/show/NCT01812278 (Archived by WebCite at http://www.webcitation.org/6yPO2OIKR). [ABSTRACT FROM AUTHOR]