Limited evidence is available about (non)-representativeness of participants in health-promoting interventions. The Dutch Healthy Primary School of the Future (HPSF)-study is a school-based study aiming to improve health through altering physical activity and dietary behaviour, that started in 2015 (registered in ClinicalTrials.gov on 14-06-2016, NCT02800616 ). The study has a response rate of 60%. A comprehensive non-responder analysis was carried out, and responders were compared with schoolchildren from the region and the Netherlands using a cross-sectional design. External sources were consulted to collect non-responder, regional, and national data regarding relevant characteristics including sex, demographics, health, and lifestyle. The Chi-square test, Mann-Whitney U test, or Student's t -test were used to analyse differences. The analyses showed that responders ( n = 494) were comparable with non-responders ( n = 348) and regional data ( n = 6172) with regard to sex and health. Responders did not significantly differ from regional data with regard to lifestyle. Responders had significantly higher educated parents compared to non-responders and were more often of autochthonous ethnicity compared to regional data. Major differences were observed between responders and schoolchildren in the Netherlands, regarding, among others sex, ethnicity, and parental employment rates. We conclude that a potential healthy-volunteer effect in the HPSF-sample is limited. External validity is high when compared to the regional population but low when compared to the national sample. For future intervention studies, we advise to evaluate outcome measures according to regional/national standards and to cooperate with external parties in early stages of research to be able to assess and enhance generalisability.

BackgroundPersistent symptoms, described as long COVID or post-COVID-19 condition, pose a potential public health problem. Here, the design and recruitment of the PRIME post-COVID study is described. PRIME post-COVID is a large-scale population-based observational study that aims to improve understanding of the occurrence, risk factors, social, physical, mental, emotional, and socioeconomic impact of post-COVID-19 condition.MethodsAn observational open cohort study was set up, with retrospective and prospective assessments on various health-conditions and health-factors (medical, demographic, social, and behavioral) based on a public health COVID-19 test and by self-report (using online questionnaires in Dutch language). Invited for participation were, as recorded in a public health registry, adults (18 years and older) who were tested for COVID-19 and had a valid Polymerase Chain Reaction (PCR) positive or negative test result, and email address. In November 2021, 61,655 individuals were invited by email to participate, these included all eligible adults who tested PCR positive between 1 June 2020 and 1 November 2021, and a sample of adults who tested negative (2:1), comparable in distribution of age, sex, municipality of residence and year-quarter of testing. New recruitment periods are planned as well. Participants are followed over time by regular follow-up measurements. Data are analyzed using the appropriate data-analyses methods.DiscussionThe PRIME post-COVID study will provide insights into various health-related aspects of post-COVID-19 condition in the context of various stages of the COVID-19 pandemic. Results will inform practical guidance for society, clinical and public health practice for the prevention and care for long-term impact of COVID-19.Trial registration ClinicalTrials.gov identifierNCT05128695.

SamenvattingDe Euregio Maas-Rijn (EMR) bestaat uit vijf grensregio’s in Nederland, België en Duitsland. Vanwege overeenkomsten als grensligging en een industrieel (mijn)verleden is hun gezondheidssituatie waarschijnlijk vergelijkbaar. Hoe ziet de gezondheidssituatie van de EMR eruit en welke factoren spelen een rol wanneer er toch gezondheidsverschillen blijken te zijn? We hebben een mixed method study uitgevoerd, waarbij we gebruikmaakten van een unieke Euregionale dataset met gegevens over aantal inwoners, geslacht, leeftijd, opleiding, werk, levensverwachting bij geboorte, mortaliteit, doodsoorzaken en overgewicht/obesitas. We hebben semigestructureerde interviews afgenomen bij 22 deskundigen uit de publieke gezondheidszorg en aanverwante beleidsterreinen, allen werkzaam binnen de EMR. Vooral de levensverwachting bij geboorte blijkt te verschillen: inwoners van de Provincie Limburg (B) leven gemiddeld 2,7 jaar langer dan de inwoners van de Provincie Luik (B) (82,5 jaar versus 79,9 jaar). Volgens stakeholders kunnen sociaal-culturele en sociaaleconomische factoren (zoals grensbarrières, een lage sociaaleconomische status) de gezondheidsverschillen binnen de EMR verklaren. De gezondheidssituatie in de EMR kan verbeterd worden door inzet op integraal beleid en het versterken van gezondheidsvaardigheden bij de lage SES-populatie.