Sample and design
The LASA COVID-19 questionnaire was sent to LASA participants on June 8, 2020, just after the first COVID-19 wave in the Netherlands. Data were recorded between June 9, 2020 and October 8, 2020. However, 99% of all data were received before the end of August 2020. Of 1701 LASA respondents that were participating in the last measurement cycle (Wave J, 2018–2019), we selected 1485 respondents. Respondents that were not selected (n = 216), already had died (n = 61) or were purposely not selected (n = 155). The latter group includes people for whom the questionnaire was expected to be too much of a burden, such as for respondents who only did a short telephone interview or had a proxy interview at the last measurement cycle (Wave J). The 1485 respondents that were selected for the COVID-19 questionnaire received a questionnaire by postal mail. Respondents were also given the opportunity to fill out the questionnaire online (digital questionnaire). The oldest respondents (aged 80+) who did not respond and were not able to complete one of the other registration modes were offered to answer the questions in a telephone interview.
Of the 1485 LASA participants who received the questionnaire, 1128 (76%) participated. Registration modes were as follows: written questionnaire (n = 909), digital questionnaire (n = 198), and telephone interview (n = 21). Reasons for non-response were: no return of questionnaire/no answer (n = 250, 16.8%), refusal (n = 60, 4.0%), deceased before approach (n = 13, 0.9%), or ineligible (n = 34, 2.3%). Non-response analyses showed that people who did not participate in the LASA COVID-19 questionnaire were lower educated (education in years, mean = 10.8 versus 11.4, p < 0.01) and had lower cognitive scores (MMSE score, mean = 27.2 versus 28.2, p < 0.001) compared to those who participated. There were no statistically significant differences in age, sex, chronic diseases and functional limitations. The LASA study [9,10,11] received approval by the medical ethics committee of the VU University medical center. All participants provided written informed consent.
Measures in the LASA COVID-19 questionnaire
An overview of the measures included in the LASA COVID-19 questionnaire is provided in Table 1. The questionnaire included measures specific for COVID-19, such as symptoms which were known to be associated with SARS-CoV-2 infection at the time, changes in access to healthcare, changes in social contact, and changes in diet and physical activity. The questions focus on the period since March 1, 2020. Most of these questions were newly developed, or came from existing population-based COVID-19 studies in the Netherlands . Details on the COVID-19-related questions are provided in Online Supplementary data (Appendix 1). Additionally, the questionnaire included a selection of measures from regular LASA measurement cycles, covering multiple domains of functioning: self-rated health, functional limitations, social contact, loneliness, mastery, depression, anxiety, advanced care planning, provision of personal/household care and use of personal/household/nursing care [10, 11].
Basic characteristics: measures
For the purpose of the current article, we provided an overview of the basic characteristics of the LASA COVID-19 questionnaire participants, as well as an overview of impactful life events during the first wave of the pandemic. Basic characteristics included age, sex, educational level, region and COVID-19 incidence among respondents and close relatives. The highest level of education attained was categorized as low (elementary school or less), medium (lower vocational or general intermediate education) or high (intermediate vocational education, general secondary school, higher vocational education, college or university). Region represents the three regions in which LASA respondents were recruited: the western part of the Netherlands (in and around Amsterdam, Water- and Wormerland), in the northeast (in and around Zwolle, Zwartewaterland and Ommen) and in the south (in and around Oss and Uden). The southern region was one the most affected areas in the Netherlands in the beginning of the pandemic, in terms of number of COVID-19 cases. COVID-19 incidence was based on self-report. Respondents were asked whether a doctor or other healthcare professional told them they probably had COVID-19, based on their symptoms, or whether they were tested positive for COVID-19. Respondents were also asked whether close relatives (partner, parent, child) were tested positive for COVID-19. We assessed the consequences of the COVID-19 pandemic and intelligent lockdown with the following question: “Are there any events in your life that occurred because of the COVID-19 crisis that strongly affect you?” This was followed by 10 different situations or life events, such as experiencing illness, having no/less contact with children or grandchildren, or experiencing financial difficulties. Response categories were: (1) strong impact, (2) moderate impact or (3) no impact.
Descriptive analyses were done in SPSS 26 (IBM Corp, Armonk, NY, USA). Mean (SD) and proportions were reported for basis characteristics and impactful situations.