Design, participants and procedures
In this study a quantitative research approach involving questionnaires was utilized. The questionnaires were disseminated online to a large panel of Dutch citizens curated by the IPSOS research agency. Panel members were invited via email and supplied with all requisite information accompanied by a formal request for informed consent. Inclusion was limited to those panel members who provided consent for their responses to be utilised in subsequent research. The data collected for this study was gathered during the period of September to December 2021. The questionnaires that were distributed to the panel members contained various items related to sample characteristics followed by multiple measurement instruments on expected utility, projected utility and health behaviour.
Questionnaire, scales and items
Sample characteristics were reported using items on ‘age’, ‘gender’, ‘health status’, ‘living area’, ‘residential region’, ‘education level’ and ‘annual income’. Either ordinal scales with ascending response categories or nominal scales with dichotomous response categories were used to measure these items. Expected utility was discerned using the EQ-5D-5L instrument combined with the time-trade-off method as both are commonly deployed for valuing health states in health economics14,15,16. The EQ-5D-5L instrument is comprised of five dimensions including ‘mobility’, ‘self-care’, ‘usual activities’, ‘pain and discomfort’ and ‘anxiety and depression’ (Supplementary material 1)14,15,16. A 5-point scale was used to measure these dimensions yielding generic health state profiles to which standard expected utility values were ascribed based on an extensive time-trade-off valuation study conducted among the Dutch population17,18. These time-trade-off studies derive expected utility values by eliciting individuals’ preferences regarding the amount of remaining life expectancy they are willing to forgo in order to avoid persisting in a suboptimal health state19,20. Projected utility was assessed using the Subjective Health Experience (SHE) ladders, which are ladder-shaped visual analogue scales developed by Bloem and Stalpers to measure how individuals expect to function physically and mentally while pursuing a life aligned with their goals within real-world constraints21,22,23,24. The SHE ladders were used to evaluate expected utility regarding ‘physical health’, ‘psychological health’, ‘social health’ and ‘general health’ for the upcoming month (Supplementary material 1)21,22,23,24. An 11-level ladder scale in which level 0 represented an estimation of the worst day of upcoming month and level 11 represented an estimation of the best day of upcoming month was deployed to determine scores21,22,23,24. Health behaviour was assessed using a newly developed and validated instrument grounded in the five health behaviour dimensions that emerged from the BRAVO@Work project25,26. This instrument encompasses these five dimensions, namely ‘exercise’, ‘nutrition’, ‘rest’, ‘smoking’ and ‘alcohol use’ alongside an overarching dimension regarding ‘general health’ that captures aspects of health behaviour not addressed by the specific items (Supplementary material 1)25,26. A 6-point Likert scale ranging from 1 = fully disagree to 6 = fully agree was deployed to measure these dimensions25,26.
Analysis, interpretation and software
Sample characteristics were examined employing descriptive statistics. Categorical variables were conveyed as percentages, whereas continuous variables were presented as means. Questionnaire characteristics were assessed through measures of construct reliability, construct validity, convergent validity and discriminant validity. Construct reliability was appraised using Cronbach’s alpha (α), rho_a and rho_c coefficients, which are considered satisfactory when their values exceed the 0.70 threshold27. Construct validity was determined by executing a factor analysis in which the instruments’ factorial structure was verified and refined by excluding redundant and cross-loading items27. Convergent validity was assessed by computing the average variance extracted (AVE) coefficient, which is regarded as adequate when its value surpasses the 0.50 threshold27. Discriminant validity was evaluated through the heterotrait-monotrait (HTMT) ratio, which was considered acceptable when it remained below the 0.90 threshold27. Model characteristics were investigated through the construction of regression models and were delineated using effect sizes, significance levels and explained variance27. Effect sizes of associations between model variables were examined via standardised Beta coefficients (β), which were interpreted as small when below 0.30, moderate when between 0.30 and 0.50 and substantial when exceeding the 0.50 threshold27. Significance levels of these associations was assessed using p-values, which are considered significant when falling below the 0.05 threshold27. Explained variance was reported through R-squared (R²) coefficients, which can be deemed small when below 0.30, moderate when between 0.30 and 0.50 and substantial when surpassing the 0.50 threshold27. Sample characteristics were derived by utilising the IBM SPSS Statistics software package Version 27, whereas questionnaire and model characteristics were extracted employing the SmartPLS software package Version 4.027,28.
Ethics statement
This study was conducted in accordance with the Declaration of Helsinki and the prevailing ethical laws, regulations and guidelines of the Netherlands, all of which are integrated into the research protocols and panel management practices of IPSOS research agency. IPSOS research agency also complies with the ICC/ESOMAR International Code on Market, Opinion and Social Research and Data Analytics as well as the ESOMAR Data Protection Checklist. IPSOS research agency further holds ISO 20252:2019 and ISO 27001 certifications. According to the Dutch Central Committee on Research Involving Human Subjects (https://www.ccmo.nl/onderzoekers/wet-en-regelgeving-voor-medisch-wetenschappelijk-onderzoek/uw-onderzoek-wmo-plichtig-of-niet) and the Dutch Medical Research Involving Human Subjects Act (https://wetten.overheid.nl/BWBR0009408/2022-07-01) ethical approval was not required for this study as it does not constitute medical-scientific research nor does it subject participants to procedures or impose behavioural obligations. All participants provided written informed consent in accordance with the privacy policy of IPSOS research agency (https://www.ipsosisay.com/nl-nl/privacy-policy).