We performed an ad-hoc survey with cross-sectional secondary data analysis (data that was collected by someone else for another primary purpose ) based on panel data. The panel belongs to the social research and market research institute Forsa (https://www.forsa.de/1/). The study sample was recruited offline and the questionnaire was provided online. Informed consent was obtained from all study participants and people were able to participate from April 21 to May 2, 2020. Contact precautions due to SARS-CoV-2 still applied during that period. For this ad-hoc survey, we followed the Declaration of Helsinki. According to statutes of the ethics committee of the Medical Faculty Charité – Universitätsmedizin Berlin, secondary data analyses do not require ethical approval according to national guidelines (Amtsblatt 230/2019, §2 Abs. 1).
The sample consisting of 1,000 informal caregivers was recruited offline from a panel of about 80,000 German-speaking people ranging in age from 40 to 85 years. The sample was weighted based on the German Ageing Survey 2014, a representative survey of 40 to 85-year-olds living in private households in Germany [23,24]. Those who reported taking care of someone aged over 60 for at least six months (i.e., inclusion criterion 1) were invited to participate in our survey. Further, the care receiver had to be allocated a level of care according to the compulsory long-term care insurance in Germany (i.e., inclusion criterion 2, from 1=low level of care to 5=high level of care  and be living at home/ in a community dwelling with or without the informal caregiver (i.e., inclusion criterion 3).
The scales used are based on or informed by established scales and were adapted to the COVID-19 situation by an interdisciplinary team consisting of psychologists, sociologists, a political scientist, a medical doctor, and a health economist who are professionals regarding burdens and challenges of informal caregivers. This is common practice in ad-hoc survey research .
Background and context of the stress process
The current context is the COVID-19 pandemic in spring 2020. Gender, age, and education level are background or contextual variables according to Pearlin and colleagues  and will be considered in our multivariate analyses. Further variables like household size, living conditions of care recipient, occupation, income per month (€), and population size of the place of residence are only used to characterize the study sample.
Five involvement indicators were: main caregiver (yes [indicator met] or no by self-definition), expenditure of time (high [indicator met] = daily for 3 to 6 hours or longer or low = once to multiple times a week for a minimum of an hour), level of care (serious level of care [indicator met] = level 3, 4, and 5 or minor level of care = level 1 and 2), dementia in care recipient (yes [indicator met]/no), professional help (day care facility and / or ambulatory care = yes/no [indicator met]). Subsequently, involvement indicators were added up to determine the mean number. The number of involvement indicators ranges from 0-5 with higher results indicate a higher involvement in care. In order to determine the level of care (i.e. the third care involvement indicator) on the basis of the German long-term care insurance guidelines according to the German Social Security Code XI, items in six modules contribute to the ﬁnal score: 1) mobility=10%; 2) either cognitive and communicative abilities; 3) behavior and psychiatric problem=15%; 4) self-care=40%; 5) dealing with requirements because of illness or therapy=20%; and 6) organization of everyday life and social contacts=15%), which are weighted differently. The score ranges from 0 to 100, with higher scores indicating worse condition. An applicant receives level of care 1 if the total score is >12.5, indicating minor impairments of autonomy or of skills; level 2 means considerable impairments, level 3 means serious, level 4 means severe, and level 5 means most severe impairments of autonomy or of skills with 90 to 100 overall points .
Change in care situation. To evaluate the change in the care situation during the coronavirus pandemic we asked informal caregivers how their personal care situation developed overall due to the coronavirus situation in the last 4 to 8 weeks on a 3-point Likert scale (much/somewhat better, no change, somewhat/much worse).
Concerns/excessive demands. Informal caregivers were asked to state to what extent the following statements apply to them and their care situation on a 4-point Likert scale with response categories ‘applies completely, applies somewhat, applies slightly, does not apply at all’. Items were 1) I’m worried about not being able to cope with home care in future; 2) My financial situation has deteriorated due to the combination of care work and the coronavirus situation; 3) I have more work because local services and support structures have been cancelled; 4) The current care situation is excessively stressful for me and 5) The current caregiving situation is excessively stressful for the person I care for. The score ranges from 5-20 with higher results indicating more concerns/excessive demands due to COVID-19.
Problems with implementation of COVID-19 measures. Informal caregivers were asked whether they are able to implement the following recommended COVID-19 measures into home care work; two answer categories were possible: (1) very well/fairly well and (2) not very well/not at all well. 1) Informing yourself about the latest official hints and recommendations on how to behave in the coronavirus situation; 2) Avoiding direct contact to other people outside your own household as far as possible; 3) Avoiding physical contact with the care receiver as far as possible (e.g., hugging, kissing or touching hands); 4) Washing your hands thoroughly with soap before and after direct contact with the care receiver; 5) Not touching your own face; 6) Explaining the coronavirus situation to the care receiver and/or reassuring them; 7) Wearing a face mask when close in contact to the care receiver, e.g. for personal hygiene; 8) Shifting contact to the care receiver increasingly to phone calls or video calls. The score ranges from 8-16 with higher results indicating more problems with implementation of COVID-19 measures.
Loss of support. Informal caregivers were asked to state whether in each of the following cases a coronavirus-related change occurred for their care recipient on a 3-point scale: no change (0), decreased (1), has stopped completely (2). The items covered support by 1) other family members or friends; 2) neighbors; 3) ambulatory care service; 4) day care; 5) a 24h-care worker from Germany; 6) a 24h-care worker from abroad; 7) other health services (e.g., chiropody); 8) family physician, and 9) other helpers [8,27]. The score ranges from 0-18 with higher results indicating more loss of support due to COVID-19.
Provision, comprehension & practicability of COVID-19 information. Informal caregivers were asked whether they agree with the following statements (strongly agree/somewhat agree/somewhat disagree/strongly disagree). The items were 1) I feel that I have access to good public information about coronavirus in Germany; 2) I feel that I can understand the public information about coronavirus and 3) I feel that I can implement the public recommendations on coronavirus effectively in the care situation. The score ranges from 3-6 with higher results indicating more problems with provision, comprehension & practicability of COVID-19 information.
Negative feelings. Informal caregivers were asked to state how the current situation affects their feelings (i.e., helplessness, emotionally stressful conflicts with the care receiver, feelings of despair, feelings of anger and rage) in relation to the care situation (i.e., decreased/no change/increased/not specified). Items were adapted from the Sense of Competence Questionnaire (SCQ)  which measures different burdens for informal caregivers, and the Geriatric Depression Scale (GDS) . The score ranges from 4-12 with higher results indicating more negative feelings due to COVID-19.
Caregiving by myself. Informal caregivers where asked whether caregiving by themselves 1) has stopped completely; 2) decreased; 3) hardly changed or 4) increased due to the COVID-19 pandemic.
Characteristics of informal caregivers were presented as mean and standard deviation (SD) for the continuous variable ‘number of involvement indicators met’ and as percentage for categorical variables. We conducted chi-square tests of homogeneity for categorical variables and Welch and t-tests for scales to evaluate differences in the COVID-19 specific constructs between the informal caregivers who met involvement indicators and those who did not. Furthermore, we used binomial logistic regression and multiple regression analysis to assess associations between the COVID-19 specific constructs and each of the dichotomous involvement indicators and the mean number of involvement indicators met. Gender, age and educational level were used as sociodemographic covariates. Analyses were performed using IBM SPSS Statistics for Windows, version 25.0 (IBM Corp., Armonk, NY, USA). P values <.05 were considered to indicate statistical significance.