Nivel Panel Stronger Together: a longitudinal probability-based cohort capturing experiences and needs of people with chronic illnesses and disabilities concerning quality of life, healthcare and participation – a cohort profile

Abstract

Purpose

The Nivel Panel Stronger Together (in Dutch: Nivel Panel Samen Sterk) is a probability-based panel, established to collect and analyse (longitudinal) data on the experiences and needs of individuals living with chronic illnesses and disabilities in the Netherlands, in specific regarding topics related to (1) quality of life, (2) healthcare and (3) participation in society.

Participants

The panel consists of approximately 3500 individuals who have a medically diagnosed chronic disease and/or a mild-to-severe physical disability. About half of the panel members (49.6%) have both a chronic disease and physical disability; 36.2% have only a chronic disease and 10.4% only a physical disability. The most prevalent chronic diseases represented in the panel are cardiovascular diseases (23.2%), chronic respiratory diseases (22.7%) and diabetes mellitus (9.2%). Of those having a physical disability, most have a mild-to-moderate disability.

Findings to date

Nivel Panel Stronger Together data are used for scientific publications, and to inform policy and practice on relevant challenges and changes regarding Dutch healthcare and participation in society. Among other things, it has been established how to support individuals with a long-term condition who experience challenges in self-management behaviours or health literacy, and what the needs of people with disabilities are in order to participate equally in society.

Future plans

We aim to establish new methods to include under-represented groups in the panel, such as young adults and those with a migration background. In addition, we are exploring options to complement self-reported panel-based survey data by linking it with routinely collected Dutch registration data.

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• The Nivel Panel Stronger Together consists of a large, continuously maintained sample that is representative of the Dutch population of people with somatic chronic diseases and/or physical disabilities.

• With more than 20 years of data collection, the panel enables the analysis and identification of long-term trends, providing policymakers with valuable data to inform their work and shape informed policies.

• The panel is based on a probability sample reducing disadvantages of volunteer patient sample.

• Young people and those with a migration background are under-represented in the panel.

Introduction

A significant portion of the global population is or will be affected by chronic illnesses.¹ Chronic diseases, such as cardiovascular diseases, cancer, chronic respiratory diseases or diabetes, are characterised by the absence of a prospect of full recovery.² In 2022, 10.4 million people in the Netherlands (59% of the population) lived with one or more chronic illnesses.³ This number is expected to increase due to increased life expectancy and unhealthy lifestyle-related factors, such as poor nutrition or physical inactivity.⁴

Individuals with chronic illnesses often face numerous challenges in their daily lives. Research has shown that a chronic illness impacts individuals’ physical, psychological and social functioning.⁵ These challenges in functioning can range from physical symptoms like pain and fatigue to psychological problems such as depression and anxiety, as well as social difficulties like stigmatisation, lagging workforce participation and strained social networks.5,8 People with chronic illnesses face various challenges of self-management, including behavioural self-management, such as taking prescribed medications, following a tailored diet and exercise routine, and attending frequent hospital visits.^{7 9} In addition, emotional self-management plays a crucial role, including stress management and coping with the illness, with support from both professional and informal networks being essential.^{9 10} Such challenges can also make it difficult to fully participate in society. Individuals with physical disabilities resulting from their chronic illness may face additional challenges related to participation. Problems may include practical obstacles, such as limited access to buildings, or social obstacles, such as prejudice. The United Nations Convention on the Rights of Persons with Disabilities states that people with disabilities have the same rights as everyone else.¹¹ In line with this, the Dutch government has enacted the Equal Treatment Act in 2016 on the basis of disability or chronic condition to promote equal participation of all citizens in society. To ensure that this objective is met, it is crucial to monitor the extent to which people with a chronic illness or disability can participate in society, and to examine the above-mentioned challenges they face regarding living with a chronic illness or disability.

The Nivel Panel Stronger Together (in Dutch: Nivel Panel Samen Sterk) is established to collect and analyse longitudinal data from a probability-based sample of individuals living with chronic illnesses and disabilities in the Netherlands. The main objective of the panel revolves around gaining insights into the experiences and needs of individuals with a medically diagnosed chronic somatic illness and/or a physical disability, specifically relating to (1) quality of life, (2) healthcare experiences and (3) participation in society. In this context, ‘participation in society’ denotes participation across multiple domains, such as daily life, (public) transportation, work, leisure and social participation. Outcomes are shared with policymakers, healthcare professionals, healthcare institutions, patient and consumer organisations and researchers. This makes the panel an important tool to inform government policy about the situation and wishes of people with a chronic illness or physical disability as well as to shape policymaking in government.

Cohort description

The panel started as the Patient Panel Chronic Illnesses (1998–2004) which was initiated by researchers from the Netherlands Institute for Health Services Research (Nivel). In 2005, the panel expanded by including people with a physical disability and continued under the name National Panel of Chronic illness and Disability (in Dutch: Nationaal Panel Chronisch zieken en Gehandicapten). In 2026, the panel has been renamed Nivel Panel Stronger Together (in Dutch: Nivel Panel Samen Sterk) to refer to the target group in a more appropriate and positive manner. The Nivel Panel Stronger Together is a nationwide probability-based panel of approximately 3500 independently living people with chronic illnesses and physical disabilities aged 18 years or older. The most commonly prevalent chronic diseases are represented in the panel, such as cardiovascular diseases, cancer, chronic respiratory diseases or diabetes. The Nivel Panel Stronger Together continuously collects data through recurring twice-yearly surveys, complemented occasionally by additional surveys, interviews or focus groups. Participants remain in the panel for several years.

Ethics

The Nivel Panel Stronger Together has its own privacy regulations, describing how the data are managed, which organisational and technical measures have been taken to protect the privacy of panel members, and which procedures are followed to implement these measures. All data are collected and handled in accordance with the privacy protection guidelines of the Dutch Data Protection Authority, the Netherlands Code of Conduct for Health Research and the Netherlands Code of Conduct for Research Integrity. Under Dutch law, approval by an ethics committee or institutional board is not obligatory for conducting questionnaire-based research including research with the Nivel Panel Stronger Together. Informed consent is obtained from all panel members.

Sampling and recruitment

Participants are recruited via two different procedures. Panel members with a chronic disease are recruited via general practitioners (GPs) using a two-stage sampling design. Panel members with a physical disability are recruited using a selection procedure nested within existing national surveys of Statistics Netherlands (in Dutch: Centraal Bureau voor de Statistiek). The unique feature of the panel is that its members are included on the basis of a probability sample and can only participate by invitation. Although this method is labour intensive and expensive, it ensures the high panel quality that is demanded for representative scientific research of the target group. To prevent selective dropout and ageing of the panel, a quarter of the participants is replaced annually.

Recruitment by general practitioners

A two-stage sampling procedure is followed for the recruitment of people with a chronic disease. First, a random, national sample of GP practices is drawn from the ‘Registration of established general practitioners’, which is administered by Nivel and in which all GP practices and GPs in the Netherlands are registered.¹² GPs from selected practices receive an invitation letter. Those who agree to participate are visited by trained research employees from Nivel, who screen a random sample of one-third of patient records (a maximum of 900 patients) against the inclusion and exclusion criteria (see box 1). Second, patients meeting the selection criteria receive a letter from their GP with information about the Nivel Panel Stronger Together and the request to participate. Enclosed is an informed consent form that, once completed and signed, can be sent—without costs—to Nivel. During the screening activities, all parties strictly adhere to privacy regulations that apply to dealing with privacy-sensitive data. GPs receive financial compensation for their participation in the screening (€350 base fee plus €1 per reviewed patient file).

Box 1. Inclusion and exclusion criteria.

Inclusion criteria

• Presence of a medically diagnosed somatic chronic disease; based on the International Classification of Primary Care.⁴⁶

• The disease is irreversible. If the latter could not be concluded on the nature of the diagnosis, the symptoms must have been known to the general practitioner for at least 1 year.

Exclusion criteria

• Younger than 18 years old.

• Insufficient command of the Dutch language.

• Mentally unable to participate.

• Not living independently.

• Unaware of the diagnosis.

• Terminally ill (a life expectancy of <6 months).

Recruitment via national surveys

People with a mild-to-severe physical disability are recruited through multiple national studies conducted by Statistics Netherlands.^{13 14} In these surveys, people are asked to indicate whether they have a long-term condition and how severely their health affects their daily activities. Statistics Netherlands selects potential panel participants who indicate to have a long-term condition affecting their daily activities, and who have agreed to be approached for future research. Statistics Netherlands sends them an invitation letter including information about the Nivel Panel Stronger Together and an informed consent form that can be signed and returned—without costs—to Nivel.

Enrolment procedure

Once people have returned the informed consent form, they are sent an intake questionnaire to provide background information on their gender, educational level, level of health literacy using the European Health Literacy Survey Qestionnaire - 16-item short version,¹⁵ health status, severity of disability¹⁶ and three most-disabling health problems. Type of chronic disease, number of chronic diseases, sex, age and region of residence are collected from the patients’ electronic record (all described in table 1), administered by GPs. A widely used self-report instrument, developed by Klerk and colleagues, is used to classify individuals’ disability severity (no, mild, moderate or severe disability) based on reported difficulties in activities of daily living and whether these activities can be performed independently.¹⁶ Individuals recruited through national surveys are enrolled for the panel if they report having a mild-to-severe disability. To determine whether they have a medically diagnosed chronic somatic disease besides their physical disability, they are asked for consent to request the medical data described above from their GP.

Table 1. Baseline characteristics of currently active panel participants (July 2024; N=3399).

Characteristic	N (%)
Age group (M, SD)	65.4, 13.8
18–39 years	202 (5.9)
40–64 years	1203 (35.4)
65–74 years	1052 (31.0)
75 years and older	942 (27.7)
Sex
Female	1852 (54.5)
Male	1547 (45.5)
Educational level
Low	737 (22.1)
Middle	1504 (45.0)
High	1100 (32.9)
Chronic disease and physical disability
Chronic disease, no physical disability	1231 (36.2)
Both chronic disease and physical disability	1687 (49.6)
Physical disability, no chronic disease	352 (10.4)
Unknown*	129 (3.8)
Type of chronic disease
Cardiovascular disease	790 (23.2)
Asthma and/or COPD	772 (22.7)
Musculoskeletal disease	227 (6.7)
Cancer	144 (4.2)
Diabetes mellitus	311 (9.2)
Neurological disease	151 (4.4)
Chronic digestive disease	113 (3.3)
Other chronic disease	410 (12.1)
No chronic disease or unknown†	481 (14.2)
Number of chronic diseases
One	1084 (31.9)
Two	968 (28.5)
Three or more	866 (25.5)
No chronic disease or unknown†	481 (14.1)
Severity of disability
No disability	1262 (38.2)
Mild disability	963 (29.2)
Moderate disability	845 (25.6)
Severe disability	231 (7.0)
Ethnicity‡
Native Dutch	2979 (89.2)
Second generation with a migration background	185 (5.5)
First generation with a migration background	177 (5.3)
Health literacy level
Insufficient	98 (2.9)
Limited	457 (13.7)
Sufficient	2789 (83.4)
Living situation
Alone	915 (27.3)
With other(s)	2440 (72.7)
Region of residence in the Netherlands
North	179 (5.3)
East	795 (23.4)
West	1521 (44.7)
South	904 (26.6)
Urbanisation of residence
Very strongly urban	499 (14.7)
Strongly urban	1156 (34.0)
Moderately urban	815 (24.0)
Slightly urban	720 (21.2)
Not urban	209 (6.2)

Multiple variables have missing data, that is,: educational level: n=58; severity of impairment: n=98, ethnicity: n=58, health literacy level: n=55, living situation: n=44.

^*Unknown due to missing data on severity of impairment on the intake questionnaire and/or missing information on medical data from the GP.

^†Unknown=these are panel members who are enrolled through national surveys and do not give permission to request their medical data from their GP.

^‡Ethnicity is based on a person’s country of birth or their parents’ country of birth47; Native Dutch=respondent and both parents born in the Netherlands, second generation=respondent born in the Netherlands, with at least one parent born abroad. First generation=respondent born abroad.

COPD, chronic obstructive pulmonary disease; GP, general practitioner.

Active panel members

Currently, there are 3399 active panel participants (see table 1). Approximately half of the panel members are female (54.5%). The majority of panel members has a chronic disease (85.8%), standing alone (36.2%) or in combination with a physical disability (49.6%); 10.4% of the people only have a physical disability. The most common chronic diseases are cardiovascular diseases (23.2%), asthma and/or chronic obstructive pulmonary disease (COPD) (22.7%) and diabetes (9.2%). Current panel members with a chronic disease have been enrolled from 79 GPs’ offices distributed throughout the Netherlands. Participants recruited via GPs more often have asthma and/or COPD, while those recruited through national surveys are more likely to have a chronic digestive disease and a moderate-to-severe disability. Differences between panel members included via the two recruitment procedures are limited to disease and disability-related characteristics and do not extend to sociodemographic characteristics such as age, sex, educational level, living situation, or ethnic background (data not shown).

Data collection, topics and response rate

Participants with a chronic illness receive a questionnaire focusing on healthcare in spring and participants with a physical disability receive a questionnaire focusing on participation in autumn; people with both a chronic illness and a physical disability receive both questionnaires. Up to and including 2022, all participants received both the spring and autumn questionnaires. To reduce participant burden, we have decided to administer the questionnaires only to those who comprise the most relevant target group. Questionnaires can be filled out online or in writing. Participants who have not completed the survey receive a maximum of two reminders: the first reminder is sent 5 weeks after the initial questionnaire, and the second reminder 4 weeks after the first reminder. At times, specific subgroups of patients receive an additional questionnaire or invitation to participate in an interview or focus group study. Participants do not receive a financial compensation for completing the questionnaires, but they regularly receive feedback on the research results via newsletters.

The surveys cover a wide range of topics (see box 2). The healthcare questionnaires focus on participants’ experienced health and their experiences with healthcare. The participation questionnaires focus on aspects such as housing, work, education and leisure activities. Where possible, we use validated questionnaires to address the topics.

Box 2. Topics included in the intake, healthcare and participation questionnaire.

Intake questionnaire

• Sociodemographics.

• Health and daily functioning.

• Health literacy with the European Health Literacy Survey Questionnaire - 16-item short version.¹⁵

Healthcare questionnaire

• Mental and physical health with the EuroQol Five Dimension Instrument⁴⁸ and daily functioning the 36-Item Short Form Health Survey.⁴⁹

• Care and support at home.

• Experiences with healthcare (professionals) and trust in healthcare.

• Coping with the chronic illness with the Illness Perception Questionnaire⁵⁰ and self-management with the Partners in Health Questionnaire.⁵¹

• Shared decision-making and communication with healthcare professionals with the Patient Reported Experience Measure Chronic Care⁵² and the Person-Centred Coordinated Care Experience Questionnaire.⁵³

• Digital applications in healthcare.

Participation questionnaire

• Participation in daily tasks and activities.

• Labour participation and leisure.

• Social contacts, societal participation and loneliness with the De Jong Gierveld Loneliness Questionnaire.⁵⁴

• Use and accessibility of facilities.

• Life satisfaction on multiple domains.

In recent years, approximately 76% of participants completed the surveys (table 2).

Table 2. Response rate 2014–2024 per measurement round.

Year	Healthcare questionnaire (spring)		Participation questionnaire (autumn)
	Sent (N)	Completed (N, %)	Sent (N)	Completed (N, %)
2014	3349	2605 (78)	3886	3121 (80)
2015	3971	3116 (79)	4496	3600 (80)
2016	4842	3498 (72)	4048	3238 (80)
2017	3998	3040 (76)	3654	2984 (82)
2018	3429	2665 (78)	3491	2640 (76)
2019	3645	2853 (78)	3647	2755 (76)
2020	3049	2382 (78)	2901	2295 (79)
2021	3114	2357 (76)	3187	2347 (74)
2022	3225	2356 (73)	3391	2520 (74)
2023	2787	2079 (75)	1799	1379 (77)
2024	2926	2060 (70)	1580	1125 (71)

Up to and including 2022, all participants received the spring and the autumn questionnaire. Since 2023, only those with a chronic illness receive the healthcare questionnaire and those with a physical disability the participation questionnaire.

Analyses

With data collected with the panel, we use a wide range of research designs and analyses to provide a comprehensive overview of the experiences and needs of individuals living with chronic illnesses and disabilities in the Netherlands. Linear and logistic regression analyses are used for cross-sectional designs to identify relationships between variables and multilevel regression analyses are used for longitudinal designs with yearly repeating questions in the questionnaires. This allows for trend analyses that inform whether shifts have occurred over time. Regression analyses are conducted as well to test for differences between subgroups. To enable the generalisation of the data to the entire population of people with chronic illnesses and/or disabilities in the Netherlands, weighted estimates for demographic and disease characteristics (ie, sex, age, educational level, type and number of chronic diseases, severity of physical disability, household, region of residence and level of urbanisation) are used in the analyses. The reference populations are compiled using mainly routinely recorded data from the Dutch population (Statistics Netherlands)¹⁷ and the healthcare sector (Nivel’s Primary Care Database).¹⁸ Research from Dutch research and knowledge institutes (The Netherlands Institute for Social Research)¹⁹ is also used. As the population changes over time, we regularly update the weights based on these reference populations.

Patient and public involvement

Since 2021, we have an advisory committee consisting of a varying number of approximately 10 former panel members. The aim of the advisory committee is to ensure that research conducted within the Nivel Panel Stronger Together aligns with the specific needs and wishes of its target group, thereby further enhancing its relevance and quality. The advisory committee is involved in setting research priorities, designing adequate research questions and questionnaires and interpreting research findings and helping to disseminate these.²⁰ Further, the panel has a programme committee, consisting of eight members plus an independently operating chair. The committee represents the two commissioners (Ministry of Health, Welfare and Sports and the Ministry of Social Affairs), knowledge institutions and patient and branch organisations. The primary task of the committee is to advise the research team about actual and upcoming issues that might be examined with the use of the panel, to approve proposed research, to review research output and to suggest ways of spreading and implementing knowledge stemming from studies undertaken with the Nivel Panel Stronger Together.

Findings to date

Scientific publications

Self-management

Multiple studies have provided insights into patients’ self-management behaviour and needs.21,24 A recent study during the COVID-19 pandemic showed that people with a chronic illness who reported mental health problems and stressors due to the pandemic experienced more changes in self-management behaviour, either improved or deteriorated self-management, than those without mental health problems and stressors.²³ Continuity of care and social support were found as important buffering factors against changes in self-management. It seems important that healthcare providers are aware of factors that may affect self-management during a healthcare crisis and provide patients with the right support.

Health literacy

Several studies have been conducted investigating health literacy, that is, the ability to access, understand, appraise and apply health-related information.25,29 Health literacy levels vary among the different studies, with about 20–40% of those with a chronic illness having inadequate or problematic health literacy levels.^{25 28 29} It has also been shown that patients with inadequate or problematic health literacy report less positive experiences with patient-centred care, shared decision-making and self-management than those with sufficient health literacy levels.²⁸

Participation in society

Various aspects relating to participation in society have been studied, such as participation in daily life including accessibility of public transport, work and leisure. For instance, social participation of older adults with chronic illnesses and/or disabilities (aged >65 years) was studied using latent class analysis.³⁰ Four classes of social participation behaviour were identified: (1) social withdrawers, (2) proximate social dwellers, (3) moderately active social dwellers and (4) pro-active social dwellers. Differences were found in background characteristics between the four types. It appeared that, for example, pro-active social dwellers have the highest levels of well-being, whereas the social withdrawers have the lowest levels. The characterisation of different types of social behavioural patterns may help community workers and municipalities identify people who are at higher risk of social withdrawal and to assess their needs. In a different study, during the Dutch national elections in 2017, the experiences of people with physical disabilities have been studied.³¹ Voter turnout and accessibility were relatively good among people with physical disabilities, and respondents overall perceived the elections as accessible. Some people did experience barriers, such as getting to the polling station or entering the station.

Policy and practice

Annual monitors

We yearly report on the experiences and needs, and potential shifts in these, of people with a chronic illness and physical disability regarding healthcare and participation topics. The results are reported in the Nivel Healthcare Monitor (in Dutch Zorgmonitor⁸) and the Nivel Participation Monitor (in Dutch Participatiemonitor³²). For example, we have shown that individuals with a disability less often participate in paid employment (46%) than people from the general Dutch population (86%). Longitudinal data show no significant improvement over the past decade.

Data of the panel are also regularly used to inform healthcare providers, policymakers and healthcare users about societally relevant issues and healthcare developments. Examples include the experiences and needs regarding e-health technology usage (E-healthmonitor³³) or the experiences and needs of specific sub-groups, such as patients with asthma, COPD and/or a rare lung disease (in Dutch Longmonitor³⁴).

Review of government programmes and insights into societal challenges

In collaboration with other parties, Nivel has used panel-based data to review government programmes for the Ministry of Health, Welfare and Sport. The currently ongoing programme Unlimited Participation (in Dutch Doe Onbeperkt Mee) describes what the government, municipalities and companies will do to improve the situation of people with a disability, in accordance with the United Nations Convention.³⁵ Panel-based data was used to test the overarching ambition of the previous edition of this programme, namely that people can participate according to their own wishes and abilities. Moreover, the Netherlands Institute for Human Rights has requested Nivel to review the implementation of the United Nations Convention of the Rights of Persons with Disabilities with panel-based data.³⁶ These and more studies have led to reports and recommendations that inform government policy on important societal challenges the Netherlands is facing, such as equal rights for people with an illness or disability,³⁷ the approach of tackling loneliness or independent living in elderly,38,40 short-term and (middle) long-term effects of the COVID-19 pandemic,⁴¹ and access to healthcare and professional client support.⁴²

Strengths and limitations

The Nivel Panel Stronger Together consists of a large, continuously maintained sample of the Dutch population with somatic chronic diseases and/or physical disabilities. With a history of more than 20 years, the panel enables the analysis and identification of long-term trends, providing policymakers with valuable data to inform their work and shape informed policies. We employ various methods to ensure a representative sample. During the recruitment procedure, random and nationwide sampling methods are used to ensure a diverse sample of GPs and potential respondents that are selected from the GP practices and Statistics Netherlands. We do not allow for people to enrol themselves for the panel to reduce potential bias of highly motivated participants filling in the surveys. We provide the possibility to complete questionnaires both online and in writing as we recognise that certain subgroups, such as individuals with limited health literacy, find it more challenging to fill out questionnaires digitally. With the above-mentioned points, we ensure a panel that is as representative and inclusive as possible. Furthermore, we collaborate closely with other panels to enable meaningful comparisons between our group’s data, the general population and other subgroups of individuals with disabilities.

The panel also has limitations. Relatively few participants who are younger than 40 years or those with a migration background enrol in the panel, and the dropout among these groups is relatively high. The twice-yearly questionnaires are long, contain many topics and are offered in Dutch only. As a result, current recruitment methods and survey content may not be sufficiently appealing to everyone, particularly to those with lower levels of health literacy and individuals who do not have strong command of the Dutch language. Nevertheless, the response rate is high with an average of 76% filling in the questionnaires, which shows the willingness of panel members to contribute to the aims of the panel in providing insight into and improving the situation of people with chronic illnesses and physical disabilities in the Netherlands.

Recent innovations and future plans

Our aim is to remain up to date regarding methodological advancements and the topics we address. We regularly evaluate and update our survey content to reflect current realities and capture relevant data. For example, we explore alternative ways of measuring and classifying disability, using the Washington Group Short Set on Functioning⁴³ and the Global Activity Limitation Indicator,⁴⁴ which are used in international research and could enhance the comparability of our findings. While we will continue to offer the option to receive surveys either on paper or digitally, we have started to encourage the use of the digital option due to its time-saving and environmental benefits. Further, we are currently exploring the setup of a young adult panel, composed of individuals below 30 years old. The objectives would be to enhance the representation of young adults within the panel and to ensure the data collection methods and survey topics (such as education, starting a first job and becoming independent) resonate with their interests and experiences. We have also started reaching more people with a migration background, and we will continue to explore the best ways to enhance the panel’s diversity.

Recently, we have successfully explored the option of linking panel-based data to Statistics Netherlands microdata, and we aim to link the survey data to other routinely collected administrative (patient) registers and draw lessons from successful examples that have implemented this approach.⁴⁵ By linking data, we get objective measures of, for example, employment history or medication prescriptions data. It also means that we can reduce the number of questions in the survey, allowing for more space to include questions about participants’ experiences and perceptions.

Collaboration

We frequently collaborate with other researchers, policymakers and government institutions. For example, universities, the Dutch National Institute for Public Health and the Environment, the Netherlands Institute for Social Research or the Netherlands Institute for Human Rights. Panel-based data can be (re)used to gain insight into the experiences and wishes of people with chronic illnesses and/or disabilities when the research aligns with the conditions established for the use of panel-based data, including meeting the mission and objectives of the Nivel Panel Stronger Together, conducting high-quality research for scientific or public purposes and approval of the research from the external programme committee. People who are interested in collaboration can contact the corresponding author or can find additional information on the website www.nivel.nl/nl/panels-en-registraties/nivel-panel-samen-sterk.

Data availability statement

Data are available upon reasonable request.