Integration of former child and adolescent study participants into a national health online panel for a longitudinal study on young adult mental health

BackgroundLongitudinal studies are essential for understanding health trajectories and determinants over time. Successfully re-engaging and monitoring participants at key stages such as the transition from adolescence to adulthood is crucial. This stage of life is characterized by many changes and challenges and is considered critical for the manifestation of mental health problems. This study addresses challenges of contacting, re-activation and comparability of individuals in transition to adulthood with the initial population-based sample last contacted up to 9 years ago.MethodsIn 2024, former participants of the "German Health Interview and Examination Survey for Children and Adolescents" (KiGGS) aged 16-25 years were invited to register in the new online panel infrastructure "Health in Germany" and participate in the "Study on Mental Health in Emerging Adulthood" (JEPSY) via a push-to-online panel approach. Logistic regression models identified predictors of registration and study participation. Weighting adjustments were applied to analyse and correct for selective participation. To assess potential selection bias, life satisfaction of JEPSY participants was benchmarked against a representative sample.ResultsAmong 11,737 invitees, 4,451 (37.9%) registered, and among these, 3,063 (68.8%) completed the JEPSY survey. For participants aged 11 + years, higher probabilities for registration and participation were evident for females (OR = 2.61 [95% CI: 2.37-2.88]); OR = 2.85, [2.56-3.18]), individuals with higher occupational (OR = 1.08, [1.04-1.13]; OR = 1.06, [1.01-1.11]) or educational status (OR = 1.13, [1.08-1.17]; OR = 1.13, [1.08-1.17]). Individuals with higher emotional problems were less likely to register (OR = 0.98, [0.97-0.99]) and participate (OR = 0.98, [0.97-0.99]). Weighting adjustments reduced biases but increased statistical variance. Benchmarking life satisfaction revealed no significant differences between JEPSY participants and their representative counterparts.ConclusionsThis study demonstrated the feasibility of re-activating former participants and integrating them into a modern online panel. While re-activation was successful for a substantial proportion of invitees, specific challenges (e.g., selective re-participation) remain. The findings provide insights for refining re-contact and retention strategies to improve representativeness and quality of longitudinal mental health research, ultimately enabling more accurate monitoring of health trajectories and their determinants over time.