Review of sample size determination methods for the intraclass correlation coefficient in the one-way analysis of variance model.

Reliability of measurement instruments providing quantitative outcomes is usually assessed by an intraclass correlation coefficient. When participants are repeatedly measured by a single rater or device, or, are each rated by a different group of raters, the intraclass correlation coefficient is based on a one-way analysis of variance model. When planning a reliability study, it is essential to determine the number of participants and measurements per participant (i.e. number of raters or number of repeated measurements). Three different sample size determination approaches under the one-way analysis of variance model were identified in the literature, all based on a confidence interval for the intraclass correlation coefficient. Although eight different confidence interval methods can be identified, Wald confidence interval with Fisher's large sample variance approximation remains most commonly used despite its well-known poor statistical properties. Therefore, a first objective of this work is comparing the statistical properties of all identified confidence interval methods-including those overlooked in previous studies. A second objective is developing a general procedure to determine the sample size using all approaches since a closed-form formula is not always available. This procedure is implemented in an R Shiny app. Finally, we provide advice for choosing an appropriate sample size determination method when planning a reliability study.

Real-Life Effectiveness of Smoking Cessation Delivery Modes: A Comparison Against Telephone Counseling and the Role of Individual Characteristics and Health Conditions in Quit Success.

INTRODUCTION: Professional behavioral counseling for smoking cessation can be delivered in many forms, which may not work equally well for everyone. We aim to explore in a real-world setting whether different delivery modes yield different rates of quit success and whether quit success varies based on gender, age, educational level, and being treated for a health condition. AIMS AND METHODS: We used monitoring data (n = 13 747) from a smoking cessation counseling provider in the Netherlands (September 2018 to August 2021) to compare differences in quit success immediately after the end of counseling and at 12-month follow-up between telephone and other modes of counseling. Participants chose which mode of counseling they received. At the 12-month follow-up, we also examined differences in quit success based on demographic characteristics and whether one is being treated for various health conditions. RESULTS: Participants of in-person group counseling and online in-company group counseling were significantly more likely to have quit immediately after the counseling compared with telephone counseling (OR = 1.25, 95% CI = 1.08-1.44; OR = 1.63, 95% CI = 1.18-2.24). Analyses revealed no significant differences in quit success between telephone and other modes of counseling after 12 months. Those treated for a respiratory or psychological condition were less likely to have maintained quit success, as were women, and participants with a lower educational level. CONCLUSIONS: When chosen by oneself, the mode of smoking cessation counseling received does not appear to be important for long-term quit success. However, certain groups warrant extra support to prevent excessive program attrition and unsuccessful quit attempts. IMPLICATIONS: Our findings suggest that when chosen by oneself, the delivery mode of smoking cessation counseling does not appear to be important for long-term quit success. This finding is of particular relevance for those who are unable to attend in-person cessation counseling due to, for instance, reduced accessibility or mobility. We also found that women, lower educated, and younger participants were more likely to dropout of the cessation program or to not have maintained a quit attempt, signaling that disparities in smoking cessation persist when standardized counseling is given, and therefore more tailored counseling may be necessary for these groups.

The ISAC Paradigm to Tame Oral Cancer in Saudi Arabia: A Quasi-experimental Study.

Late detection of oral cancer (OC) cases in Saudi Arabia is concerning. It reduces survival rate and complicates treatment. The ISAC intervention was developed to bridge the gaps observed in dentists' practice of OC examination and patient education. The ISAC stands for I, informing patients of OC screenings; S, screening for OC; A, advising high-risk patients to quit risk factors; and C, connecting patients to advanced services. This study tested the potential effect of the ISAC in influencing dentists' cognitive and behavioral skills, to enhance early detection and prevention of OC. A quasi-experimental study was conducted among dental interns (DIs) at dental setting to test the effect on comprehensive oral cancer examination score (COCE), awareness, self-efficacy, descriptive-norms, and self-reported behavior. Data were collected through triangulation of methods pre and post the intervention at two-months. Multiple linear mixed effects regression models were utilized for data analysis. Between October 2020 and April 2021, 47 DIs participated in the study. The final model showed the significant effects of time (ISAC) on COCE (95% CI = 25.12-29.42, P < .001). DIs had a significant improvement in awareness, self-efficacy, descriptive norms, and self-reported behavior. The findings showed promising effects of the intervention toward the early detection and prevention of OC. Dentists, dental organizations, and policymakers in areas with a high risk of OC could benefit from the current intervention which contributes to capacity building and improved community health. A pragmatic study with a robust design is needed to test the effectiveness of the intervention on a wider scale.

Best (but oft forgotten) practices: Efficient sample sizes for commonly used trial designs.

Designing studies such that they have a high level of power to detect an effect or association of interest is an important tool to improve the quality and reproducibility of findings from such studies. Since resources (research subjects, time, and money) are scarce, it is important to obtain sufficient power with minimum use of such resources. For commonly used randomized trials of the treatment effect on a continuous outcome, designs are presented that minimize the number of subjects or the amount of research budget when aiming for a desired power level. This concerns the optimal allocation of subjects to treatments and, in case of nested designs such as cluster-randomized trials and multicenter trials, also the optimal number of centers versus the number of persons per center. Since such optimal designs require knowledge of parameters of the analysis model that are not known in the design stage, in particular outcome variances, maximin designs are presented. These designs guarantee a prespecified power level for plausible ranges of the unknown parameters and minimize research costs for the worst-case values of these parameters. The focus is on a 2-group parallel design, the AB/BA crossover design, and cluster-randomized and multicenter trials with a continuous outcome. How to calculate sample sizes for maximin designs is illustrated for examples from nutrition. Several computer programs that are helpful in calculating sample sizes for optimal and maximin designs are discussed as well as some results on optimal designs for other types of outcomes.

Smokers' strategies to reduce tobacco spending: self-reported use and differences across subgroups. Findings from the International Tobacco Control (ITC) Netherlands Survey.

BACKGROUND: The cost of tobacco is one of the most reported reasons for smoking cessation. Rather than quitting, smokers can use also strategies to reduce tobacco expenditure while continuing smoking, such as smoking less or using price-minimising strategies. The Netherlands announced to increase the price of a pack cigarettes from seven (2018) to ten euros (2023), to reduce tobacco prevalence and consumption. This study explores the self-reported strategies to reduce tobacco spending among Dutch smokers, and whether this differed per age, income, and education. Additionally, we analysed among quitters in these subgroups whether price played a role in their decision to quit. METHODS: Cross-sectional survey data from the International Tobacco Control (ITC) Netherlands Wave 2 (September-November 2020, N = 1915) was used. Strategies to reduce spending among smokers (N = 1790) were: reducing consumption, bulk buying, switching to cheaper products or buying from low-taxed sources. These were collapsed into: reducing consumption (solely or in combination with other behaviours), solely price-minimising behaviours (such as buying cheaper brands), or no strategies to reduce spending. Associations between strategies and characteristics were analysed through multinomial and binary logistic regression models. Second, we explored which subgroups were more likely to report that price played a role in their decision to quit among quitters (N = 125). RESULTS: The majority of smokers used strategies to reduce tobacco spending: 35.6% reduced consumption and 19.3% used solely price-minimising strategies. 82.1% of quitters reported that price played a role in their decision to quit. Low-income individuals were more likely to report price as a reason for quitting and reduce consumption, but also to buy cheaper products. Highly nicotine dependent smokers were more likely to use price-minimising behaviours, and less likely to reduce consumption. CONCLUSIONS: The majority reported using strategies to reduce spending or that price played a role in their decision to quit. Reducing consumption was the most reported strategy. Low-income smokers were more likely to reportedly reduce consumption, buy cheaper products, or quit. Price policies have the potential to reduce socioeconomic inequalities in smoking. To discourage price-minimising behaviours, such as switching to cheaper products, reducing price differences between products should be prioritized.

Exploring the gateway hypothesis of e-cigarettes and tobacco: a prospective replication study among adolescents in the Netherlands and Flanders.

BACKGROUND: Studies demonstrated that adolescent e-cigarette use is associated with subsequent tobacco smoking, commonly referred to as the gateway effect. However, most studies only investigated gateways from e-cigarettes to tobacco smoking. This study replicates a cornerstone study revealing a positive association between both adolescent e-cigarette use and subsequent tobacco use; and tobacco and subsequent e-cigarette use in the Netherlands and Flanders. DESIGN: The longitudinal design included baseline (n=2839) and 6-month (n=1276) and 12-month (n=1025) follow-up surveys among a school-based cohort (mean age: 13.62). Ten high schools were recruited as a convenience sample. The analyses involved (1) associations of baseline e-cigarette use and subsequent tobacco smoking among never smokers; (2) associations of e-cigarette use frequency at baseline and tobacco smoking frequency at follow-up; and (3) the association of baseline tobacco smoking and subsequent e-cigarette use among non-users of e-cigarettes. FINDINGS: Consistent with prior findings, baseline e-cigarette use was associated with higher odds of tobacco smoking at 6-month (OR=1.89; 95% CI 1.05 to 3.37) and 12-month (OR=5.63; 95% CI 3.04 to 10.42) follow-ups. More frequent use of e-cigarettes at baseline was associated with more frequent smoking at follow-ups. Baseline tobacco smoking was associated with subsequent e-cigarette use (OR=3.10; 95% CI 1.58 to 6.06 at both follow-ups). CONCLUSION: Our study replicated the positive relation between e-cigarette use and tobacco smoking in both directions for adolescents. This may mean that the gateway works in two directions, that e-cigarette and tobacco use share common risk factors, or that both mechanisms apply.

Sample size calculation and optimal design for regression-based norming of tests and questionnaires.

To prevent mistakes in psychological assessment, the precision of test norms is important. This can be achieved by drawing a large normative sample and using regression-based norming. Based on that norming method, a procedure for sample size planning to make inference on Z-scores and percentile rank scores is proposed. Sampling variance formulas for these norm statistics are derived and used to obtain the optimal design, that is, the optimal predictor distribution, for the normative sample, thereby maximizing precision of estimation. This is done under five regression models with a quantitative and a categorical predictor, differing in whether they allow for interaction and nonlinearity. Efficient robust designs are given in case of uncertainty about the regression model. Furthermore, formulas are provided to compute the normative sample size such that individuals' positions relative to the derived norms can be assessed with prespecified power and precision. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Trends in Individualized Affordability of Factory-Made Cigarettes: Findings of the 2008-2020 International Tobacco Control Netherlands Surveys.

INTRODUCTION: Cigarette affordability, the price of tobacco relative to consumer income, is a key determinant of tobacco consumption. AIMS AND METHODS: This study examined trends over 12 years in individualized factory-made cigarette affordability in the Netherlands, and whether these trends differed by sex, age, and education. Data from 10 waves (2008-2020) of the International Tobacco Control Netherlands Surveys were used to estimate individualized affordability, measured as the percentage of income required to buy 100 cigarette packs (Relative Income Price [RIP]), using self-reported prices and income. The higher the RIP, the less affordable cigarettes are. Generalized estimating equation regression models assessed trends in individualized affordability over time and by sex, age, and education. RESULTS: Affordability decreased significantly between 2008 and 2020, with RIP increasing from 1.89% (2008) to 2.64% (2020) (p ≤ .001), except for 2008-2010, no significant year-on-year changes in affordability were found. Lower affordability was found among subgroups who have a lower income level: Females (vs. males), 18-24 and 25-39-year-olds (vs. 55 years and over) and low or moderate-educated individuals (vs. highly educated). Interactions between wave and education (p = .007) were found, but not with sex (p = .653) or age (p = .295). A decreasing linear trend in affordability was found for moderately (p = .041) and high-educated (p = .025), but not for low-educated individuals (p = .149). CONCLUSIONS: Cigarettes in the Netherlands have become less affordable between 2008 and 2020, yet this was mostly because of the decrease in affordability between 2008 and 2010. There is a need for more significant increases in tax to further decrease affordability. IMPLICATIONS: Our findings suggest that cigarettes have become less affordable in the Netherlands between 2008 and 2020. But, this appears to be the result of a steep decrease in affordability between 2008 and 2010. Affordability was lower among groups who have on average lower incomes (females, young adults, and low- and moderate-educated individuals), and differences in trends across education levels could be explained by per capita income changes. Our individualized measure indicated lower affordability than published aggregate affordability estimations. Future tax increases should be large enough to result in a lower affordability.

Price minimizing behaviours by smokers in Europe (2006-20): evidence from the International Tobacco Control Project.

BACKGROUND: Effectiveness of tobacco taxation can be undermined through smokers applying price-minimizing behaviours rather than quitting or reducing consumption. Common price-minimizing strategies are buying cheaper tobacco [discount brands or roll-your-own (RYO) tobacco], bulk buying and cross-border purchasing. This study analyses trends in and factors associated with such behaviours in four European countries from 2006 to 2020. METHODS: Data came from adult smokers participating in the International Tobacco Control (ITC) Surveys conducted between 2006 and 2020 in England (9 waves, n = 768-4149), France (4 waves, n = 1415-1735), Germany (5 waves, n = 513-1515) and the Netherlands (10 waves, n = 1191-2177). Country-specific generalized estimating equation regression models were fit to assess trends in smoking RYO tobacco, discount brands, bulk buying and cross-border purchasing within the European Union. RESULTS: Buying discount brands or RYO tobacco was the most common strategy in all countries, except France. Except for buying discount brands, estimates of price-minimizing behaviours were highest in France (2019: RYO = 27.2%, discount brands = 17.3%, bulk buying = 34.1%, cross-border purchasing = 34.2%), and lowest in Germany (2018: RYO = 18.6%, discount brands = 43.7%, bulk buying = 8.0%, cross-border purchasing = 9.8%). Direction and magnitude of trends differed by country, and behaviour. Young smokers were less likely to buy in bulk. Low-income and low-education smokers were more likely to purchase RYO tobacco or discount brands. The association with discount brands was not found for French low-income smokers. CONCLUSIONS: Smoking cheaper tobacco is the most prevalent price-minimizing strategy in three countries (England, Germany and Netherlands), and more prevalent among low-income individuals. Harmonizing prices across products and countries would reduce switching to cheaper tobacco.

Research protocol: Cervical Arthroplasty Cost Effectiveness Study (CACES): economic evaluation of anterior cervical discectomy with arthroplasty (ACDA) versus anterior cervical discectomy with fusion (ACDF) in the surgical treatment of cervical degenerative disc disease - a randomized controlled trial.

INTRODUCTION: To date, there is no consensus on which anterior surgical technique is more cost-effective in treating cervical degenerative disc disease (CDDD). The most commonly used surgical treatment for patients with single- or multi-level symptomatic CDDD is anterior cervical discectomy with fusion (ACDF). However, new complaints of radiculopathy and/or myelopathy commonly develop at adjacent levels, also known as clinical adjacent segment pathology (CASP). The extent to which kinematics, surgery-induced fusion, natural history, and progression of disease play a role in the development of CASP remains unclear. Anterior cervical discectomy with arthroplasty (ACDA) is another treatment option that is thought to reduce the incidence of CASP by preserving motion in the operated segment. While ACDA is often discouraged, as the implant costs are higher while the clinical outcomes are similar to ACDF, preventing CASP might be a reason for ACDA to be a more cost-effective technique in the long term. METHODS AND ANALYSIS: In this randomized controlled trial, patients will be randomized to receive ACDF or ACDA in a 1:1 ratio. Adult patients with single- or multi-level CDDD and symptoms of radiculopathy and/or myelopathy will be included. The primary outcome is cost-effectiveness and cost-utility of both techniques from a healthcare and societal perspective. Secondary objectives are the differences in clinical and radiological outcomes between the two techniques, as well as the qualitative process surrounding anterior decompression surgery. All outcomes will be measured at baseline and every 6 months until 4 years post-surgery. DISCUSSION: High-quality evidence regarding the cost-effectiveness of both ACDA and ACDF is lacking; to date, there are no prospective trials from a societal perspective. Considering the aging of the population and the rising healthcare costs, there is an urgent need for a solid clinical cost-effectiveness trial addressing this question. TRIAL REGISTRATION: ClinicalTrials.gov NCT04623593. Registered on 29 September 2020.

Non-smoking adolescents' perceptions of dissuasive cigarettes.

Introduction: Dissuasive cigarettes, cigarettes with an unappealing colour or displaying a health warning label, may deter young people from smoking uptake. Methods: Two online surveys were conducted with non-smokers aged 12-17 to explore perceptions of cigarette appeal, harm and product trial. Study 1 was a within-subject study which examined perceptions of four cigarettes with different coloured paper, and four cigarettes displaying a warning. Study 2 was a between-subject study (with limited power), in which respondents were randomized to one of four cigarettes: (1) regular cigarette; (2) least favourable warning from Study 1; (3) least favourable colour from Study 1; or (4) a combination of the least favourable warning and colour from Study 1. Warnings or colours were considered least favourable when they had lower scores on appeal, harm, and product trial. Results: In Study 1, a cigarette featuring the warning 'cancer, heart disease, stroke' and a drab dark brown cigarette were rated lowest on appeal and trial intentions, and highest on perceived harm. In Study 2, there were no significant differences in perceptions of appeal, harm or trial intentions between the regular and dissuasive cigarettes. Conclusions: Findings from our within-subject study suggest that a cigarette displaying the text 'cancer, heart disease, stroke' and a drab dark brown coloured cigarette are most dissuasive for Dutch non-smoking adolescents. Whether dissuasive cigarettes reduce appeal, reduce product trial, or increase perceptions of harm compared to a regular cigarette should be further examined in larger between-subject studies.

Demand for Factory-Made Cigarettes and Roll-Your-Own Tobacco and Differences Between Age and Socioeconomic Groups: Findings From the International Tobacco Control Netherlands Survey.

INTRODUCTION: Macroeconomic studies have shown that young individuals who smoke, and have a low socioeconomic status respond more strongly to price increases. Most of this evidence stems from research on factory-made (FM) cigarettes. With the rising popularity of roll-your-own (RYO) tobacco, there is a need for studies on cigarette demand that distinguish between both. AIMS AND METHODS: This study examined whether individual demand differed for FM and RYO tobacco, and across age, and socioeconomic (income and education) groups. Purchase tasks for FM and RYO cigarettes were included in the 2020 International Tobacco Control (ITC) Netherlands Survey. Adults who smoke daily (n = 1620) stated how many cigarettes they would smoke in 24 hours across eight prices. Four demand indices were derived: intensity (consumption at zero costs), alpha (rate of change in elasticity), Pmax (turning point elasticity), and breakpoint (lowest price where consumption equals zero). The indices were tested for subgroup differences. RESULTS: Individuals who smoke RYO tobacco indicated higher intensity, and greater alpha than individuals who smoke FM cigarettes. Participants aged 25-39 had lower Pmax, and 18-24 year olds displayed higher breakpoints. Participants with low income displayed higher intensity, and lower Pmax than other income groups. No associations were found with education. CONCLUSIONS: Individuals who smoke RYO tobacco indicated higher price sensitivity than those smoking FM cigarettes, supporting the need to harmonize tobacco taxation. Taxation may be especially beneficial to reducing consumption among individuals with a low income or smoke RYO tobacco. Substantially higher prices are needed in the Netherlands to achieve the desired results. IMPLICATIONS: Individuals who smoke daily were willing to pay substantially higher prices than the current market prices, indicating the room and need for much higher taxation levels. Demand for RYO tobacco was more sensitive to price changes than demand for FM cigarettes. Taxation should be raised at equivalent rates for FM and RYO cigarettes. Taxation appears to be especially effective in reducing consumption among people who smoke RYO tobacco and low-income individuals. It remains important to combine increased taxation with other tobacco control measures.

Maximin design of cluster randomized trials with heterogeneous costs and variances.

Cluster randomized trials evaluate the effect of a treatment on persons nested within clusters, with clusters being randomly assigned to treatment. The optimal sample size at the cluster and person level depends on the study cost per cluster and per person, and the outcome variance at the cluster and the person level. The variances are unknown in the design stage and can differ between treatment arms. As a solution, this paper presents a Maximin design that maximizes the minimum relative efficiency (relative to the optimal design) over the variance parameter space, for trials with two treatment arms and a quantitative outcome. This maximin relative efficiency design (MMRED) is compared with a published Maximin design which maximizes the minimum efficiency (MMED). Both designs are also compared with the optimal designs for homogeneous costs and variances (balanced design) and heterogeneous costs and homogeneous variances (cost-conscious design), for a range of variances based upon three published trials. Whereas the MMED is balanced under high uncertainty about the treatment-to-control variance ratio, the MMRED then tends towards a balanced budget allocation between arms, leading to an unbalanced sample size allocation if costs are heterogeneous, similar to the cost-conscious design. Further, the MMRED corresponds to an optimal design for an intraclass correlation (ICC) in the lower half of the assumed ICC range (optimistic), whereas the MMED is the optimal design for the maximum ICC within the ICC range (pessimistic). Attention is given to the effect of the Welch-Satterthwaite degrees of freedom for treatment effect testing on the design efficiencies.

Moral distress and ethical climate in intensive care medicine during COVID-19: a nationwide study.

BACKGROUND: The COVID-19 pandemic has created ethical challenges for intensive care unit (ICU) professionals, potentially causing moral distress. This study explored the levels and causes of moral distress and the ethical climate in Dutch ICUs during COVID-19. METHODS: An extended version of the Measurement of Moral Distress for Healthcare Professionals (MMD-HP) and Ethical Decision Making Climate Questionnaire (EDMCQ) were online distributed among all 84 ICUs. Moral distress scores in nurses and intensivists were compared with the historical control group one year before COVID-19. RESULTS: Three hundred forty-five nurses (70.7%), 40 intensivists (8.2%), and 103 supporting staff (21.1%) completed the survey. Moral distress levels were higher for nurses than supporting staff. Moral distress levels in intensivists did not differ significantly from those of nurses and supporting staff. "Inadequate emotional support for patients and their families" was the highest-ranked cause of moral distress for all groups of professionals. Of all factors, all professions rated the ethical climate most positively regarding the culture of mutual respect,  ethical awareness and support. "Culture of not avoiding end-of-life-decisions" and "Self-reflective and empowering leadership" received the lowest mean scores. Moral distress scores during COVID-19 were significantly lower for ICU nurses (p < 0.001) and intensivists (p < 0.05) compared to one year prior. CONCLUSION: Levels and causes of moral distress vary between ICU professionals and differ from the historical control group. Targeted interventions that address moral distress during a crisis are desirable to improve the mental health and retention of ICU professionals and the quality of patient care.

Factors associated with primary health care providers' alcohol screening behavior in Colombia, Mexico and Peru.

Background: Screening for unhealthy alcohol use in routine consultations can aid primary health care (PHC) providers in detecting patients with hazardous or harmful consumption and providing them with appropriate care. As part of larger trial testing strategies to improve implementation of alcohol screening in PHC, this study investigated the motivational (role security, therapeutic commitment, self-efficacy) and organizational context (leadership, work culture, resources, monitoring, community engagement) factors that were associated with the proportion of adult patients screened with AUDIT-C by PHC providers in Colombia, Mexico and Peru. Additionally, the study investigated whether the effect of the factors interacted with implementation strategies and the country. Methods: Pen-and-paper questionnaires were completed by 386 providers at the start of their study participation (79% female, Mage = 39.5, 37.6% doctors, 15.0% nurses, 9.6% psychologists, 37.8% other professional roles). They were allocated to one of four intervention arms: control group; short training only; short training in presence of municipal support; and standard (long) training in presence of municipal support. Providers documented their screening practice during the five-month implementation period. Data were collected between April 2019 and March 2020. Results: Negative binomial regression analysis found an inverse relationship of role security with the proportion of screened patients. Self-efficacy was associated with an increase in the proportion of screened patients only amongst Mexican providers. Support from leadership (formal leader in organization) was the only significant organizational context factor, but only in non-control arms. Conclusion: Higher self-efficacy is a relevant factor in settings where screening practice is already ongoing. Leadership support can enhance effects of implementation strategies.

A Web-Based Computer-Tailored Program to Improve Treatment Adherence in Patients With Type 2 Diabetes: Randomized Controlled Trial.

BACKGROUND: Adherence to core type 2 diabetes mellitus (T2DM) treatment behaviors is suboptimal, and nonadherence is generally not limited to one treatment behavior. The internet holds promise for programs that aim to improve adherence. We developed a computer-tailored eHealth program for patients with T2DM to improve their treatment adherence, that is, adherence to both a healthy lifestyle and medical behaviors. OBJECTIVE: The objective of this study is to examine the effectiveness of the eHealth program in a randomized controlled trial. METHODS: Patients with T2DM were recruited by their health professionals and randomized into either the intervention group, that is, access to the eHealth program for 6 months, or a waiting-list control group. In total, 478 participants completed the baseline questionnaire, of which 234 gained access to the eHealth program. Of the 478 participants, 323 were male and 155 were female, the mean age was 60 years, and the participants had unfavorable BMI and HbA1c levels on average. Outcome data were collected through web-based assessments on physical activity (PA) levels, caloric intake from unhealthy snacks, and adherence to oral hypoglycemic agents (OHAs) and insulin therapy. Changes to separate behaviors were standardized and summed into a composite change score representing changes in the overall treatment adherence. Further standardization of this composite change score yielded the primary outcome, which can be interpreted as Cohen d (effect size). Standardized change scores observed in separate behaviors acted as secondary outcomes. Mixed linear regression analyses were conducted to examine the effectiveness of the intervention on overall and separate treatment behavior adherence, accommodating relevant covariates and patient nesting. RESULTS: After the 6-month follow-up assessment, 47.4% (111/234) of participants in the intervention group and 72.5% (177/244) of participants in the control group were retained. The overall treatment adherence improved significantly in the intervention group compared with the control group, reflected by a small effect size (d=0.27; 95% CI 0.032 to 0.509; P=.03). When considering changes in separate treatment behaviors, a significant decrease was observed only in caloric intake from unhealthy snacks in comparison with the control group (d=0.36; 95% CI 0.136 to 0.584; P=.002). For adherence to PA (d=-0.14; 95% CI -0.388 to 0.109; P=.27), OHAs (d=0.27; 95% CI -0.027 to 0.457; P=.08), and insulin therapy (d=0.35; 95% CI -0.066 to 0.773; P=.10), no significant changes were observed. These results from the unadjusted analyses were comparable with the results of the adjusted analyses, the per-protocol analyses, and the sensitivity analyses. CONCLUSIONS: Our multibehavior program significantly improved the overall treatment adherence compared with the control group. To further enhance the impact of the intervention in the personal, societal, and economic areas, a wide-scale implementation of our eHealth intervention is suggested. TRIAL REGISTRATION: Netherlands Trial Register NL664; https://www.trialregister.nl/trial/6664.

Optimal two-stage sampling for mean estimation in multilevel populations when cluster size is informative.

To estimate the mean of a quantitative variable in a hierarchical population, it is logistically convenient to sample in two stages (two-stage sampling), i.e. selecting first clusters, and then individuals from the sampled clusters. Allowing cluster size to vary in the population and to be related to the mean of the outcome variable of interest (informative cluster size), the following competing sampling designs are considered: sampling clusters with probability proportional to cluster size, and then the same number of individuals per cluster; drawing clusters with equal probability, and then the same percentage of individuals per cluster; and selecting clusters with equal probability, and then the same number of individuals per cluster. For each design, optimal sample sizes are derived under a budget constraint. The three optimal two-stage sampling designs are compared, in terms of efficiency, with each other and with simple random sampling of individuals. Sampling clusters with probability proportional to size is recommended. To overcome the dependency of the optimal design on unknown nuisance parameters, maximin designs are derived. The results are illustrated, assuming probability proportional to size sampling of clusters, with the planning of a hypothetical survey to compare adolescent alcohol consumption between France and Italy.

How Financial Incentives Increase Smoking Cessation: A Two-Level Path Analysis.

INTRODUCTION: Financial incentives effectively increase smoking cessation rates, but it is unclear via which psychological mechanisms incentives influence quit behavior. The current study examines how receiving financial incentives for smoking cessation leads to quitting smoking and investigates several mediators and moderators of that relationship. AIMS AND METHODS: The study sample consisted of 604 tobacco-smoking employees from 61 companies in the Netherlands who completed a baseline and follow-up questionnaire. The current study is a secondary analysis from a cluster randomized trial where employees received smoking cessation group counseling at the workplace. Participants in the intervention group additionally received financial incentives of €350 in total for 12-month continuous smoking abstinence. We used a two-level path analysis to test a model that assesses the effects of financial incentives through smoking cessation program evaluation, medication use, nicotine replacement use, attitudes, self-efficacy, and social influences on quit success. We additionally tested whether an individual's reward responsiveness moderated the influence of incentives on quit success. RESULTS: The effect of financial incentives on quit success was mediated by a higher self-efficacy. Financial incentives were also associated with a higher use of cessation medication. A more positive program evaluation was related to higher self-efficacy, more social influence to quit, and more positive attitudes about quitting. The results did not differ significantly by individual reward responsiveness. CONCLUSIONS: The results of the current study suggest that financial incentives may be used to increase medication use and self-efficacy for quitting smoking, which offers an indirect way to increase successful smoking cessation. IMPLICATIONS: (1) This is the first study investigating via which psychological pathways financial incentives for quitting smoking can lead to long-term quit success. (2) The results showed a path between financial incentives and a higher likelihood of medication use. Incentives may encourage smokers to use medication in order to increase their chance of quitting smoking and receive the reward. (3) There was a path from financial incentives to quit success via a higher self-efficacy. (4) The effects of financial incentives did not depend on individual reward responsiveness.

A Web-Based, Computer-Tailored Intervention to Reduce Alcohol Consumption and Binge Drinking Among Spanish Adolescents: Cluster Randomized Controlled Trial.

BACKGROUND: Alcohol consumption, including binge drinking (BD) and heavy episodic drinking (HED), is one of the leading risk factors among Spanish adolescents leading to significant social, health, and economic consequences. Reduction of BD and HED in adolescents can be achieved using Web-based, computer-tailored (CT) interventions, providing highly personalized feedback that is adapted to a person's individual characteristics and needs. Randomized controlled trials assessing the effects of tailored BD reduction programs among Spanish adolescents are scarce. OBJECTIVE: The aim of this study was to test the effectiveness of the Web-based, CT intervention Alerta Alcohol, aimed at the prevention of BD in Spanish adolescents. As a secondary outcome, effects on HED, weekly consumption, and any consumption were also assessed. The adherence and process evaluation were assessed. METHODS: A cluster randomized controlled trial conducted among 15 Spanish schools was developed. Each school was randomized into either an experimental condition (EC) (N=742) or a control condition (CC) (N=505). Finally, 351 participants for the EC and 261 for the CC were included in the analysis (N=612). Baseline assessment took place in January and February 2017. Demographic variables and alcohol use were assessed at baseline. Follow-up assessment of alcohol use took place 4 months later in May and June 2017. Participants were compared according to their randomization group (EC versus CC). After the baseline assessment, participants in the EC started the intervention, which consisted of short stories about BD, in which CT feedback was based on the I-Change Model for behavior change. Participants in the CC group only received the baseline questionnaire. Effects of the intervention were assessed using a three-level mixed logistic regression analysis for BD, HED, and any consumption, and a three-level mixed linear regression analysis for weekly consumption. RESULTS: In total, 1247 adolescents participated in the baseline assessment and 612 participated in the follow-up assessment; the attrition rate was 50.92%. The intervention was effective in reducing HED among adolescents; the odds of HED in the CC was nine times that in the experimental condition (P=.04). No effects were found for BD, weekly consumption, and any consumption. Process evaluations revealed that the adolescents were satisfied with the program (68.8%), would use the program again (52.9%), and would recommend it to someone else (62.8%). Females and non-binge drinkers showed better responses in the process evaluation. CONCLUSIONS: Our intervention was effective regarding HED but not regarding BD, weekly consumption, and any consumption. It may be that limiting alcohol consumption to prevent HED was easier in the Spanish context than it was to carry out further steps, such as reducing other patterns of alcohol consumption. Hence, additional actions are needed to accomplish these latter goals, including community approaches and policy actions aimed at denormalizing alcohol consumption among Spanish adolescents. TRIAL REGISTRATION: ClinicalTrials.gov NCT03288896; https://clinicaltrials.gov/ct2/show/NCT03288896. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR2-10.1186/s12889-018-5346-4.

An overview of mixture modelling for latent evolutions in longitudinal data: Modelling approaches, fit statistics and software.

The use of finite mixture modelling (FMM) is becoming increasingly popular for the analysis of longitudinal repeated measures data. FMMs assist in identifying latent classes following similar paths of temporal development. This paper aims to address the confusion experienced by practitioners new to these methods by introducing the various available techniques, which includes an overview of their interrelatedness and applicability. Our focus will be on the commonly used model-based approaches which comprise latent class growth analysis (LCGA), group-based trajectory models (GBTM), and growth mixture modelling (GMM). We discuss criteria for model selection, highlight often encountered challenges and unresolved issues in model fitting, showcase model availability in software, and illustrate a model selection strategy using an applied example.