The study was initiated in early 2021 at University Medicine Halle (Saale), a mid-sized city of roughly 230,000 people. The immediate trigger was the pandemic: researchers needed rapid, repeated data on infections, vaccinations and testing behaviour. But from the outset, the team had a longer ambition in view. DigiHero was conceived as a permanent research platform for studying chronic diseases, mental health, health behaviour and healthy ageing. It has since become part of the German Center for Mental Health, contributing directly to that institution’s research agenda on the mental wellbeing of the population.

Recruitment relied on two complementary strategies. The first was classical, population-based sampling: invitation letters sent by postal mail in five waves, with addresses obtained from local registration offices, service providers or a federal data portal in line with German data protection rules. The campaign began in Halle, where all 120,000 households received an invitation, then spread across Saxony-Anhalt, Saxony and Thuringia before expanding to randomly selected NUTS-2 regions in the remaining federal states. Large cities with more than 500,000 inhabitants were deliberately included to represent Germany’s urban centres, with 90,000 addresses selected in each of the city-states Berlin and Hamburg and 60,000 in Magdeburg. In total, about four million households received a postal invitation between January 2021 and February 2025. The second strategy was continuous open registration through the study website, supported by media campaigns, radio spots and press releases. Around 14 percent of participants registered without a personal invitation letter, and the researchers can compare these self-recruited volunteers with the invited sample in their analyses.

Eligibility was defined broadly: anyone born between 1936 and 2003, corresponding to ages 18 to 85 in 2021, with a main residence in an invited municipality, an internet connection, a personal email address and sufficient German language skills. To enable household-level studies, such as investigations of how respiratory viruses spread within families, the team maximised the number of participating households by inviting only one person, an anchor, per household sharing an identical address and surname. The result is a cohort that covers both dense urban districts and remote rural regions, something the designers say distinguishes DigiHero from study-centre-based cohorts tied to single locations.

Once registered, participants complete a baseline questionnaire covering sociodemographic characteristics, and then enter a rhythm of four regular contacts per year. All surveys run on LimeSurvey, an open-source platform hosted on an internal web server in a demilitarised zone within the IT infrastructure of University Medicine Halle. Each participant is linked to a 15-digit alphanumeric pseudonym that connects responses across questionnaires, and the software automatically saves progress, so a questionnaire can be paused and resumed on any device, from desktop to smartphone. Up to two reminders are sent per survey, ten to fourteen days apart, and participants can skip individual questionnaires without leaving the cohort entirely. Beyond the regular cycle, the design allows rapid additional invitations: when Russia invaded Ukraine in early 2022, the team fielded a mental health survey just one week after the war began, and a follow-up six months later. A similar rapid-response survey captured heat-related stress during the summer 2024 heatwave.

What has the cohort actually delivered? Its early findings have already shaped the scientific understanding of post-COVID condition. In an analysis of roughly 17,000 participants with at least one SARS-CoV-2 infection, the researchers found a substantially lower risk of ongoing symptoms after infections with newer virus variants, and evidence that people infected previously without developing post-COVID had a reduced risk after a subsequent infection. Vaccination, they concluded, protects indirectly by lowering the risk and severity of infection rather than reducing post-COVID risk after a breakthrough infection. A dedicated post-COVID registry now follows more than 4,000 participants at six-month intervals, over 1,000 of whom still report ongoing symptoms. In a separate analysis, fewer than 40 percent of respondents reported being symptom-free one year after infection, underscoring how persistent the condition can be.

The cohort has also quantified the pandemic’s continuing burden on respiratory health. In the winter season 2022/23, approximately 38,000 participants reported their acute respiratory infections and test results, allowing the team to calculate that SARS-CoV-2 contributed an additional 21 percent of acute respiratory infections, equivalent to roughly 17 million extra infections across the German population. Household transmission subprojects in the winters of 2022 and 2023 combined self-collected dry blood samples and nasal swabs with symptom diaries, linking self-reported data to immunological measurements. On the mental health side, the rapid Ukraine-war surveys showed that media exposure to the conflict drove a substantial rise in anxiety symptoms, exceeding levels observed during the pandemic, with people from lower-income households especially affected. Another study comparing post-COVID and depressive disorders across 45 mental health variables found markedly different symptom structures, with the largest gaps in exhaustion, fatigue, impaired task completion and reduced resilience.

Methodologically, DigiHero occupies a distinctive position in the German research landscape. Established cohorts such as KORA, SHIP, CARLA, Recall and the national NAKO study rely on physical study centres, which constrains how often participants can be recontacted and how quickly results can be produced. DigiHero’s fully virtual design integrates research into participants’ daily lives, reduces paper waste and transport resources, and permits much more frequent measurement of change over time. A two-stage design allows broad data collection across the whole cohort followed by in-depth assessment of defined subgroups, an approach particularly useful for studying rare exposures and rare diseases. Future plans include linking self-reported data with health insurance records for validation, connecting postal addresses to geospatial environmental data through open-source sources such as OpenStreetMap, exporting data from wearables and GPS movement tracking, conducting app-based cognitive testing, and even building an embedded multigenerational cohort by including family members.

The researchers are candid about the limitations. Response rates ranged from 1.2 to 8 percent depending on the recruitment area, and the cohort overrepresents people with higher education while underrepresenting those born outside Germany, a well-documented pattern of selection bias in modern cohort studies. Participation also requires internet access and an email address, though in 2023, 99 percent of German households had active internet access and about 83 percent of internet users sent and received emails, so the excluded share of the population is small. Previous work by the group showed that online-only surveys yield answers similar to mixed-mode designs across a wide range of health questions. Compared with German census data, DigiHero participants are better educated than the general population, but the gap is substantially smaller than for other established population-based studies such as ALLBUS, SOEP, SHARE or NAKO.

Data protection is built into the architecture. Names and postal addresses sit on an internet-disconnected computer in a separate database, follow-up responses are stored on the LimeSurvey server, and strict role-based access rights ensure that no individual can link identities to responses, a linkage performed only when a participant withdraws consent and requests deletion. The Ethics Committee of Martin Luther University Halle-Wittenberg approved the study, and new questionnaires must pass ethics review before deployment. There is no defined end point, and the team intends to follow participants indefinitely, building a comprehensive health database spanning diseases, behaviour, mental health and contextual factors. Data are available to researchers through a Use and Access Committee, and the consortium welcomes national and international collaborations with institutions in countries offering data protection comparable to Germany’s. The next milestone is citizen science: a digital dialogue in which participants themselves propose health topics and help shape the research agenda. In a field where the gap between a health crisis and the evidence needed to respond can stretch into years, DigiHero’s bet is that a cohort built for speed, flexibility and scale can close it.

Subject of Research: A nationwide fully digital population-based prospective cohort study in Germany for research on diseases, mental health and healthy ageing

Article Title: Prospective cohort study for digital health research in Germany (DigiHero): objectives, design and baseline characteristics

Article References: Klee, B., Diexer, S., Glaser, N., Gottschick, C., Frost, J., Massag, J., Pfrommer, L. R., Herrmann, T., Purschke, O., Schmidt, A., Dierks, C., Frese, T., Gekle, M., Girndt, M., Hettmer, S., Heuser, M., Höll, J. I., Moor, I., Rosendahl, J., … Mikolajczyk, R. (2026). Prospective cohort study for digital health research in Germany (DigiHero): objectives, design and baseline characteristics. European Journal of Epidemiology. https://doi.org/10.1007/s10654-026-01454-7

Image Credits: AI Generated

DOI: 10.1007/s10654-026-01454-7

Keywords: DigiHero, digital health, cohort study, epidemiology, COVID-19, post-COVID condition, mental health, Germany, public health, online surveys, wearables, population-based research

A new study published in Obesity Science & Practice set out to test whether a surprisingly low-tech solution could close that gap: asking study participants to photograph their medication. The research, conducted by a team at the University of Michigan, evaluated the feasibility of a photo-review protocol for online GLP-1RA studies, in which participants upload deidentified images of their injector pens, vials, labels, or prescription documents. The goal was to determine whether such images could be collected reliably, coded systematically by trained reviewers, and compared against what participants simply claimed to be taking. The answer, on all three counts, was yes, and the discrepancies the method uncovered are striking enough to matter for anyone interpreting online survey data on these blockbuster drugs.

The study design was deliberately rigorous for an online survey. Researchers recruited through Prolific, an online research platform, applying prescreening filters that restricted access to United States residents with a 99 percent or higher approval rate, at least 50 prior submissions, and self-reported current use of Ozempic or another GLP-1RA. Prospective participants were told upfront that they would need to upload a photo of their medication. A screening survey assessed whether they used an injectable semaglutide or tirzepatide product, took it once weekly, and had been on it for at least three months. Eligible participants then completed a longer main survey covering demographics, anthropometrics, prescriber type, payer type, and self-reported medication identity.

The privacy procedures were a central feature of the protocol rather than an afterthought. Participants were instructed to show the medication label while hiding personal identifying information such as names and dates of birth. A study author then reviewed every uploaded image, edited out any identifiers that slipped through, deleted the unredacted originals, and stored only redacted copies in a secure folder. For the coding stage, two trained research staff members who had no role in eligibility screening and were blinded to participants’ self-reports independently classified each photo into one of five categories: Ozempic, Wegovy, Mounjaro, Zepbound, or a compounded semaglutide or tirzepatide product. Any disagreement between the two coders went to an independent adjudicator who had not seen the images before and was also blinded to self-reports.

The mechanics of classification were straightforward but consequential. A photo was coded as a branded, FDA-approved formulation when the medication itself, its labeling, or associated records displayed the brand name. It was coded as compounded when the image showed semaglutide or tirzepatide as the active ingredient but no brand name appeared anywhere. Of the 419 completed screening responses, 47 participants were excluded for reasons ranging from insufficient duration of use to uploading photos of an ineligible drug, most commonly Trulicity, or submitting images that appeared to be stock photos. Twenty-two participants were excluded on the basis of their medication photos alone, a demonstration that the review process had real screening power. The final analytic sample comprised 322 adults with a mean age of about 45 years and a mean pre-treatment body mass index of roughly 40.

On the feasibility question, the results were emphatic. Uploaded photos generally contained enough information for coders to make a determination, and intercoder agreement before adjudication was almost perfect, with a Cohen’s kappa of 0.98. Only five discrepancies arose between the two primary coders, including one foreign-language injector pen label and several branded products, and all were resolved through adjudication. In an era when online health surveys are often dismissed as noisy or unverifiable, the demonstration that ordinary participants can and will submit usable photographic documentation of their medications is itself a methodological advance.

The more provocative findings emerged when photo-based classifications were compared with self-report. Overall agreement between the two methods was substantial, at 82.61 percent with a kappa of 0.78, but the pattern of disagreement was highly uneven. Among the 83 participants whose photos were coded as compounded semaglutide or tirzepatide products, more than a quarter of the entire sample, 65 percent self-reported using a branded medication such as Ozempic, Wegovy, Mounjaro, or Zepbound. Only 29 of the 83 compounded users, or about 35 percent, gave answers consistent with compounded use. By contrast, discrepancies between two branded products were almost nonexistent, amounting to just two cases in the whole sample.

When medication types were collapsed into branded versus compounded groups, the diagnostic statistics told a sharper story. Self-report showed perfect specificity and perfect positive predictive value, meaning that everyone who claimed a compounded product genuinely had one, and no branded user was misclassified as compounded. But sensitivity was only about 35 percent, and the negative predictive value was roughly 82 percent, indicating that a large share of compounded users were invisible to self-report. In practical terms, an online study relying purely on participant claims would have underestimated compounded GLP-1RA use by nearly two-thirds within this sample, potentially biasing any conclusions about effectiveness, side effects, or user experience.

The authors are careful to note that the survey instrument itself may share some blame. The medication-type item offered only the four FDA-approved brand names, an unsure option, and a write-in field labeled none of the above; there was no explicit response option for compounded products. Because all participants had already confirmed injectable semaglutide or tirzepatide use, write-in answers were treated as concordant with compounded classification. The researchers recommend that future studies include explicit compounded response options, pilot-test how participants understand terms like compounded and non-branded, and use cognitive interviewing or randomized wording experiments to refine the instruments. They also advise warning participants in advance about photo requirements, listing acceptable documentation forms, and considering photographs taken with the survey visible in the background to deter fraudulent submissions.

Several limitations temper the conclusions. The stringent prescreening filters identified only about 1,200 eligible participants from a pool of more than 300,000 verified platform users, and highly experienced survey takers may be unusually attentive and compliant, meaning the observed discordance could be conservative. Photo-based classification also cannot confirm the authenticity or chemical contents of a medication; it verifies only what is visible on labels and documentation, and it was not validated against dispensing records or laboratory assays. Still, the protocol draws on established clinical traditions, including brown bag medication reviews and the practice of verifying contraceptive pill packs in reproductive health research, and adapts them to a scalable online format. As GLP-1RA use continues to spread across telehealth, med spas, and compounded channels, the study suggests that a simple photograph, reviewed blindly and coded carefully, may become an essential tool for keeping online medication research honest.

Subject of Research: Feasibility of a medication photo-review protocol for classifying GLP-1 receptor agonist use in online survey research

Article Title: Improving Medication Classification in GLP‐1RA Research: Feasibility of a Photo‐Review Protocol

Article References: Katz, J. M., Gearhardt, A. N., & Griauzde, D. H. (2026). Improving Medication Classification in GLP‐1RA Research: Feasibility of a Photo‐Review Protocol. Obesity Science & Practice, 12(5), Article e70200. https://doi.org/10.1002/osp4.70200

Image Credits: AI Generated

DOI: 10.1002/osp4.70200

Keywords: GLP-1 receptor agonists, semaglutide, tirzepatide, compounded medications, medication photo review, online surveys, self-report validity, obesity research, telehealth, medication classification, research methods, Ozempic