Abstract
Background: Depression and anxiety are among the most common mental health issues of older populations, and as such they are frequently monitored covariates. The possibilities for collecting research data has grown with the recent emergence of user-friendly online survey platforms. However, to what extent the populations of older persons who participate in such research are similar to the general population remains unclear. We investigated the affective health of an open online sample of older adults (65+) in contrast to a representative randomised in-person interview sample. Methods: The surveys were conducted in 2021 during the COVID-19 pandemic in the Czech Republic after the second wave of anti-COVID-19 vaccination. The online sample (N = 389) was recruited via the Internet. Participants of the in-person study (N = 633) were randomly approached according to quotas for representativeness. The administered questionnaires included a health status self-report, the Geriatric Depression Scale (GDS) and the Geriatric Anxiety Inventory - Short form (GAI-SF). Results: Online participants reported better mental and general health; that is, they reported fewer depressive and anxiety symptoms than the randomised representative sample. In both samples, women showed higher levels of anxiety than men. Subjective general health was associated with mental health. In the randomised representative sample, in contrast to the online sample, the level of depression increased significantly with age. The open non-randomised calls for participants attracted a higher percentage of women and people with higher education than are in the general older population. Conclusions: Older research volunteers recruited online can be expected to be subjectively healthier and to differ largely from the general population in their sociodemographic characteristics.