Older people’s experiences of visiting social day centres: The importance of doing and being for health and well-being

Abstract

Background

Social day centres can support active and healthy ageing amongst older people. However, little is known regarding the importance of social day centres.

Aims/Objectives

The aim of this study was to explore how older people visiting social day centres perceive the day centres’ social influence on their health and well-being.

Material and methods

Twenty older persons attending social day centres on a regular basis were interviewed regarding activities at the day centre and their importance for active and healthy ageing. The data were analysed using qualitative content analysis.

Results

The social day centres were described as arenas to provide a structure (and something to do) in the visitor’s everyday life. By attending a day centre, the participants created a social context with other visitors. Staff acted as facilitators for visitors, helping them to interact with other visitors and to experience the feeling of being needed by others.

Conclusions

The findings suggest that social day centres are important arenas for creating a sense of context and belongingness amongst older people.

Significance

This study provides knowledge on how doing and being contribute to healthy and active ageing.

Keywords:

• Active ageing
• activities
• elderly
• healthy ageing
• social belongingness

Introduction

The proportion of the population aged over 60 is the most rapidly growing age group due to demographical changes. A growing population of older people will pose challenges for societies all over the world to catering for older people’s health and care needs [1]. Therefore, there is a need to support older people in achieving active and healthy ageing [2,3]. This is also the case in Sweden, where the population is assumed to consist of a growing older population. It has been predicted that this growing population of older people will live longer with chronic diseases or impairments [4]. This implies helping people to age in place, for example by receiving person-centred and integrated care, but also offering social care services such as self-care, home care services, meals-on-wheels, or other rehabilitation interventions, with the intention of reducing the need to move to special housing [5]. However, since the older population is heterogeneous [6,7], interventions need to be designed according to the individuals’ experiences and specific needs [8].

The World Health Organization [WHO] has stated that important aspects for healthy ageing are person-centred and integrated care and age-friendly environments which offer an opportunity to develop and maintain functional ability when ageing. Being able to engage in meaningful activities is an important part of healthy ageing [2]. Interventions that promote active and healthy ageing should be designed with empathy, autonomy, and privacy in mind [2] and with the possibility to create relationships that are deeper and long-lasting and that reduce loneliness and social isolation [6].

From an occupational perspective, the importance of doing, being, becoming, and belonging has been theorised in relation to the WHO concept of health and well-being [9]. Central to this perspective is the understanding of people as occupational beings, explained by the aspects of doing, being, becoming, and belonging, which, when integrated, contribute to health and well-being [9,10]. Doing is often used as an alternative word for occupation, to describe what we do. Being reflects on an individual experience of the doing, who we are and how we present ourselves to others through our doings. Becoming involves having a capacity for progression and striving for self-realisation through doing and being. Belonging means to be with other people and obtain a feeling of acceptance of self through shared occupations. People that experience both doing and being have possibilities to enhance their feelings of both becoming and belonging and thereby experience health and well-being [10].

One way to establish doings and being for older people are day centres, which are arenas that provide various services to cater to the diverse needs of older people [11]. Day centres for older persons are often described as having a medical or a social function [11,12]. At medical day centres, rehabilitation and health services are usually provided [11,13], while social day centres provide opportunities for older people to meet others in similar situations to themselves, and therefore at day centres new friendships can be developed [14,15]. Social day centres could influence health and well-being by enabling social participation, which is described as interacting with other people, doing things together, or being part of a context [16] and doing activities that are meaningful for the individual [17].

Previous research has shown that older people may experience a sense of purpose, and feelings of being needed by others when attending a day centre [16]. It has been argued that engagement in different activities or social gatherings at social day centres makes it possible for older people to preserve their functions [18,19], and enhance their quality of life [13,20,21]. Other studies have found that day centres may enable engagement in meaningful social interactions [22], reduce feelings of loneliness [23], and provide emotional support from other older people [24]. However, as there are few studies on the feasibility outcomes such as cost-effectiveness and satisfaction of day centres [15,16], a lack of a standardized definition of day centres, and there are different legislative contexts governing day centres in different countries, it is challenging to compare and conclude on the outcomes of day centres for older people [13,21].

In Sweden, day centres are organised to cater for either medical or social needs amongst older people. Medical day centres are organised to provide rehabilitation [11,12], and access to these types of day centres is based on the person’s health and care needs and hence, a needs assessment is often a prerequisite to taking advantage of this service [25]. Social day centres on the other hand focus on older people as a group and are thereby open for everyone to attend, without any formal decision [25]. They are organised to provide activities that stimulate social interactions amongst the participants. Research regarding the impact of day centres on health and well-being has, at least in Sweden, mostly been conducted regarding medical day centres with services mainly for persons with psychiatric or intellectual disabilities [26–29].

Although there is an increased interest in how to promote health and well-being amongst older people, little attention has been paid to older people themselves and what they believe contributes to them experiencing health and well-being, especially regarding social day centres. Previous research on active and healthy ageing suggests that the social aspects of meeting and interacting with other older people are important when participating in various physical activities programmes [30]. Therefore, the aim of this study was to explore how older people who attend social day centres perceive the day centres’ social influence on their health and well-being.

Method

This study is part of a larger project that aims to describe staff’s and participants’ experiences of social day centres for older people, and how these day centres can affect perceived health and well-being. The perspective of the staff regarding day centres is presented in a previous study [31].

Material and methods

Data collection

This study has been designed in accordance with the Declaration of Helsinki [32] regarding ethical principles guiding research that involves human subjects. Before the data collection began, the operating manager of social day centres for older people in one Swedish municipality was given information about the present study’s aim and methodology. The operating manager agreed that data collection could be carried out at the day centres which the manager was responsible for. In total, the studied municipality had 13 social day centres, of which four were in rural areas. The frequency of offered activities varied amongst the different centres: activities on some weekdays, every weekday and on every day of the week. Offered activities included both sitting and standing gymnastics, quizzes, various games, cafe activities, singing, film screening and more. The number of visitors at the day centres varied from a few to about 30–50 for certain activities. Informants for this study were recruited at three of the social day centres, one with activities organized on some weekdays, one with activities on every weekday (both morning and afternoon), and one with activities on weekdays and also on weekends.

To recruit older people, convenience sampling [33] was used. That meant in this study, that available potential participants were invited to participate based on the criterion: older people visiting a social day centre on a regular basis.

Initially, during the recruitment process of participants, information was given about the aim, the research procedure, and what was expected of those who chose to participate in the study. This information was conveyed at social gatherings at the social day centres when the whole group of visitors were gathered together. At the same time, written information about the study and contact information for the researcher was distributed to potential participants. All attending visitors were then asked individually if they were interested in participating in this study. The three social day centres that were the subjects of this study were visited by members of the research group on multiple occasions to inform and recruit participants. Twenty (20) older people who attended social day centres agreed to participate and a time and place were determined for the interview. Before starting the interview, participants were given information once again about the study, confidentiality, and the opportunity to withdraw consent to participate without any reason. All participants then gave their written informed consent to participate in the present study. Confidentiality has been strived for throughout the process of collecting and analysing data. In the quotations provided in this study, names and places have been pseudonymised.

The interviews were semi-structured [34] and concerned activities at the social day centres, and the importance of them for older people in relation to the WHO’s [2] concepts of active and healthy ageing. Question areas were, besides demographic background information, the activities and their significance for health, participation and living an active life in relation to the social day centre. While semi-structured interviews cover pre-specified themes or areas and prepared questions, they also offer flexibility to alter these questions and pose follow-up questions in response to the interviewee’s answer [34]. Thereby, semi-structured interviews provide a more detailed and comprehensive understanding of the studied phenomenon from the participant’s perspective. Interviews for this study were conducted at the social day centres, the participant’s home or at the university’s facilities. The first and last author together with a registered occupational therapist with previous experience of interviewing older people conducted the interviews. The duration of the interviews ranged from 22 to 131 min, with an average of 55 min. The data collection occurred in 2019. All interviews were audio-recorded and then transcribed verbatim by members of the research group.

Participants

In total, 20 older people who visited social day centres on a regular basis participated in the present study, six men and 14 women. The age of the participants ranged from 69 to 90 years with an average of 81 years. All participants had one or several impairments/diseases affecting everyday life such as diabetes, heart diseases, pulmonary diseases, physical restrictions, neurological disorders, visual or hearing impairment, or cancer.

Eleven were widowers/widows, four were married and five were living without a spouse. The participants were living in their ordinary housing, a few with support from home care services. Eleven of the participants attended the day centre daily and nine informants on a weekly basis (i.e. one to three days each week). Sixteen of the participants had attended a day centre for more than five years and only one less than one year. Three of the participants attended more than one day centre in the municipality. Four of the participants stressed that the reason they attended the day centres was to participate in physical exercises, and not to socialise with the other visitors. See Table 1 for demographic information on the participants.

Table 1. Demographic information on participants, N = 20.

Gender	Female	14
	Male	6
Age	Median (years)	80.5
	Range (years)	69-90
Marital status	Widow	11
	Living with spouse	4
	Living without spouse	5

Data analysis

The analytical process in qualitative research often begins when the interviews are conducted or when transcribing the collected data [35]. When conducting the interviews and transcribing the audio recordings from the interviews, it became clear that many of the participants in this study experienced feelings of loneliness as most of them lived by themselves and had few significant others. In the interviews, the participants described the importance of the other visitors and staff working at the day centre for catering for their need to socialise with others. Based on these descriptions provided by the participants, the aim of the present study was developed.

The data analysis was data-driven and conducted with qualitative content analysis [36]. All transcripts were read several times by all authors to gain a sense of the whole data set. Text that was relevant to the aim of the present study was identified and extracted from the transcripts by the first author (i.e. text that referred to other people visiting or working at the day centre and their significance for the participants’ health and well-being). These extractions were compiled into a single text and constituted the unit of analysis. Thus, all collected data were treated as a single unit that served as the basis for the continued analysis. The unit of analysis was then divided into 240 meaning units. Meaning units are paragraphs, sentences, or words that contain aspects related to each other through their context and content relevant to the aim of the study [36]. The last author condensed and labelled all meaning units with a code. Examples of codes used in this phase of the analytical process were: doing things together, being greeted by staff, feelings of being part of a group. All condensed meaning units and codes were then validated by the first author and dissimilarities were discussed to reach consensus. All condensed meaning units and codes were then used by the third and last author to construct preliminary categories based on the content that shared a commonality. A discussion, based on these preliminary categories, was conducted among all the authors to formulate the three final categories presented in the findings section. The analytical process was not linear [36]. Therefore, during these various phases of the analytical process, the authors moved between the unit of analysis and parts of the text to understand utterances in relation to their context. The analysis was conducted on the original transcription in Swedish. Illustrative quotations have been translated and are presented throughout the findings section to increase the trustworthiness of the presented findings. Translation is not an easy or straightforward process as it might be difficult to match the English translation to the Swedish verbal content. This is due to differences in syntax, expressions and word order [37]. Therefore, when translating the quotations into English the intention has been to convey the participants’ narrative as brought forward in the interviews.

Ethical approval

Ethical approval for this study was obtained through the Regional Ethical Review Board (Dnr 2018/188-31).

Findings

The social day centres were described by the participants to provide a structure (and something to do) in the participant’s everyday life. By attending a day centre, the participants created a social context with other visitors. Staff acted as facilitators for visitors to interact with other visitors and to experience feelings of being needed by others.

The categories and key findings are presented in Table 2.

Table 2. Categories and key findings.

Categories	Key findings
Providing a structure (and something to do) in the participant’s everyday life	To have something to do with others
Creating a social context between visitors	An arena to meet people
	To socialise with others
The staff act as facilitators and provide a sense of security	Create social belonging
	Safety net for visitors

Providing a structure (and something to do) in the participant’s everyday life

The daily routines of the participants had changed as they aged due to the loss of friends and spouses as well as a consequence of losing abilities to perform previous activities due to physical impairments or restrictions. Their participation at social day centres was described as a way of creating and maintaining a structure, a routine in their everyday life, by having people to meet and something to do. ‘I go there as if I were going to work and it has become a routine for me to do this’ P19. To attend the day centre the participants said that they had to make routines or structure their daily activities, such as scheduling when to wake up, and when to get dressed (e.g. being properly dressed to meet others outside their home) to attend the day centre. The participants said that they looked forward to visiting the day centre, to have something to do with other people.

Well, I think that [the day centre] means, first of all, going out. You have a goal, somewhere to go to. So, it means quite a lot. I have got a lot of acquaintances here too. You talk for a while and so on P05.

The participants described the importance of being offered various activities at the social day centre as different activities appealed to different people. It was stressed by the participants that activities offered had to be suitable or in accordance with their abilities, interests, and needs. For a few of the participants, the activity was described as the reason they attended. These participants said that they had social contacts with other people outside the day centre and attended activities at the day centre to retain their physical abilities. One prominent activity described by these informants was physical exercises. ‘I get exercise every day […] otherwise I might not have gone out for several days […] I'm actually more alert’ P28. Nonetheless, most of the participants argued that the activity itself was not important; to meet other people and enjoy their company over a cup of coffee was described as the most important contribution of the day centre. When conducting activities, the participants described the importance of enjoying themselves, having fun and laughing together.

I participate in the Music Crossword [a popular radio show in Sweden broadcast weekly since the 1960s] and today we will sew and knit, and the knitting is still left at home and that is a good thing, but we are also talking P18.

It was said that most of the visitors at the day centre did not have the strength to take part in the activities or that impairments such as reduced hearing or physical limitations made it difficult for them to engage in activities. Hence, activities could have an exclusionary effect as some would be unable to keep up with the other visitors, not only in relation to physically challenging activities but also in relation to hearing impairments or cognitive decline which made it difficult for them to hear what was said or understand instructions.

Creating a social context in-between visitors

The participants said that day centres had enabled them to create new social relationships with other older people who visited the centres. These new acquaintances had the same age and living situation as them, often living in the same geographical area. ‘It is not the easiest thing to find friends when you are as old as I am. No it’s not. There is not anyone left’ P04. The day centre provided an arena for the visitors to meet other people, which meant that fellowship with others could be established. When doing activities with others, boredom was reduced or even disappeared. Thereby, day centres were described as one way to socialise with others. Togetherness with others at day centres was raised as important to avoid feelings of loneliness. The view was frequently expressed by the participants that if they did not attend a social day centre, they would probably spend most of their time alone at home.

I mean, why should one sit here [the interview was carried out in the participant’s home] alone and glare and stare. Then it is better to go down [to the day centre] and talk to others even though you don’t have the same opinions and likes P14.

The participants said that who the other visitors were had an impact on the atmosphere at the day centre. They said that it was important to meet like-minded people of the same age. To converse with each other was frequently expressed by the participants as a significant reason for attending the day centre; to have someone to talk with rather than being alone at home doing nothing. When interacting with each other, the participants said that some topics, such as politics, were avoided to ensure that a pleasant atmosphere was created amongst the visitors. Instead, conversations revolved around football, historic local events and so forth. Occasionally, discord appeared amongst the visitors, which had a negative effect on the visitor’s mood. In relation to this, the participants described diverse ways of reacting as some took an active stance, raising their voice against how participants treated each other. Meanwhile, others tried not to get involved and, in some cases, even decided not to visit the day centre for a period after a dispute.

…they’re kind of dominant, some ladies. But it’s not certain people see it that way, but I can see some that I know then are a little bit sarcastic, a little bit like that, oh I don’t understand why you should be like that when you’re so old. No, I don’t do that. But they are, oh some ladies are at sandbox level, oh it’s not easy oh to fight with them then. Not fighting in the true meaning of the word. No, it’s not. Because they think they know everything P01.

But mostly, discussions amongst the visitors were portrayed as important to fill a void of not having other people to interact with, and hence, most visitors respected the unspoken agreement that some topics should not be discussed or raised.

Some of the participants said that the other visitors at the day centres had little significance to them as they perceived that they had little in common since their life history, socio-economic status, values and so forth differed. What made them relevant to each other was mainly the fact that they were older and lived in the same geographical area with few other significant others or relatives near their homes. The day centre was depicted as a neutral arena where the participants could meet on their own terms. Some participants said that they did not want to let the other visitors into their homes, and therefore they did not meet each other outside the day centre.

Even if I sit and knit every single day it sometimes gets boring. It is more cheerful and lively when one enters the day centre. Everyone is welcoming you “Now here she is again” they say when I have been away for a while. So, you always feel welcome P25.

The staff act as facilitators and provide a sense of security

The role of the staff in creating a context at the day centres for visitors to meet others and take part in activities was expressed as significant by the participants. Staff created the context of social togetherness at the day centre, both amongst visitors and with staff. Staff were described as creating a pleasant atmosphere between different visitors at the social day centre and were in general portrayed by all participants as being friendly, happy, and alert. The atmosphere the staff created was natural and easy going, and they were able to make the visitors enthusiastic about the activities carried out at the day centre. ‘They are there for us and they are very accommodating. They take care of us and are positive and happy. One feels that one is welcome there [at the day centre]’ P24.

The participants said that staff joined the visitors in activities, and they had fun and laughed together. According to the participants, the staff made sure that everyone was included and seen, something that was expressed as important. Staff were perceived to act the same towards all visitors and were not biased in their treatment of different visitors.

[Staff] should be like Lilly [an appreciated staff member] and have radiance, be happy and alert. And should treat us all equally and not have any favourites. And that is probably a bit difficult [for them]. And if someone is rowdy, they should handle it P19.

Furthermore, staff were portrayed as people you could talk to, trust and be comforted by. One participant said that when his wife passed away, staff took time for him in his moment of grief and sat down with him, thereby prioritizing providing comfort to him despite neglecting other visitors and work chores. Hence, staff had the function of a safety net for visitors needing support and someone to talk to about their worries.

It is very important that the leader [staff] is a positive and happy person who has a lot of ideas. But it is not certain that everything is possible to do or that we [as visitors] want to do it. But it is a person who can be enthusiastic as well as really get people on board with what we are doing. I think that is important. And then as a person [staff] should be people that you can come to and talk to if one feels like it at a certain time P25.

The participants said that staff’s actions were important to achieve a pleasant atmosphere at the day centre. Staff were described by the participants as taking a personal interest in the visitors. The participants said that as visitors they felt welcomed and cared for. Furthermore, staff were described as the ones who best understood the visitor’s needs and interests. ‘The staff know us and what our needs are and everything, so it is great’ P08. They also made sure to greet all participants and said goodbye, often with hugs, which made the participants feel that they mattered. Some participants said if they had not visited the day centre for a while, staff looked for them – and even knocked on their doors – to make sure that everything was all right with them.

The staff were described as helping the participants to feel included at the day centre. For example, staff asking for help with certain chores, delegating responsibility or getting the visitors to interact with each other. When asked by the staff to help with organising or carrying out activities, the participants said that they felt needed and that they could contribute to others as well. ‘I think it is enjoyable, I get something out of it as I feel needed. How should I phrase it, I fill a function by helping more and others’ P20.

Discussion

This study provides an understanding of how social day centres for older people, that are open for anyone to attend, are experienced by those older people who live in the community and visit these centres. Social day centres were described by the participants as becoming more important over time as they provide a structure for daily routines when one has lost friends and spouses. To attend a social day centre also affects loneliness, which could be experienced with the loss of near relationships. Social day centres provide an arena [31] where doing, being, becoming and belonging [9] are facilitated, and thus they contribute to health and well-being.

As the findings of this study suggest, those participating at these day centres are in need of a context where they can meet other people to interact and socialise with, but still on their own terms. According to this study, older people prefer to meet at the day centre as it is a neutral arena. This suggests that integrity is important as they would like to be a part of the group but on their own terms (e.g. deciding when to attend the day centre, what activities to attend, what to disclose about themselves and to whom). In comparison, older people institutionalised at various care facilities are often described as being stripped of their autonomy and integrity as the institutional process occurs (see for example [38]). When organising this type of service (i.e. day centre), the visitors should share some commonalities in interest, age, and remaining abilities [39,40]. If a visitor differs too much from the norm of the other visitors, there is a risk that that person may be subject to ‘othering’ by the other participants, with negative consequences for their participation in activities [39]. Our results suggest that the participants differed and handled their differences by for example avoiding certain topics when interacting visitor-to-visitor but also created a bond with the staff. This contributed to experiences of being seen and part of a context of belonging.

Attending the social day centre also prevented loneliness, according to the participants. By doing things together, boredom and loneliness were counteracted. Loneliness and lack of social interaction are risk factors for achieving healthy ageing [6]. Experiencing loneliness can occur at all ages but it is a common problem amongst older people [41] as different factors such as physical limitations, reduced hearing, or vision [6] and reduced social networks limit the opportunities for social contacts [42]. In this regard, the social day centre as an arena for social contacts with peers is vital, as older people visiting the day centre gain a sense of social belongingness which counteracts loneliness. Previous research [16] has raised the positive experience of being needed by others at the day centres, which is also present in our findings and suggests that day centres are of value for creating a context of social belongingness.

In the results of this study, the main activity scheduled was not always described as the main reason the participants attended the day centre. Rather, it seemed as if they needed to interact with others to show themselves as part of the community, to belong. In an interview study involving older people institutionalised at residential care facilities, van’t Leven and Jonsson [43] found two diverse ways of participating in meaningful activities; ‘doing themselves’ and ‘being in the atmosphere of the doing’. This suggests that that ‘[t]he atmosphere and belonging to the group is more important than the actual doing’ [43 p.151]. To be part of a group doing meaningful activities together may to some extent be enough to experience belongingness and participation in activities. Our results also suggest that activities scheduled at day centres may not be the actual activities that the participants were interested in. We argue, based on our findings, that the main activity, to some extent hidden, was to have a conversation with peers and thereby experience belongingness with other people. Other studies have concluded that to attract visitors to day centres there is a need for a variety of programmes of activities to cater to different needs concerning the older person’s health condition, interests, and skills [23,44,45]. Hence, there is a need for further research on how to organise social day centres and what activities to offer to promote health and well-being.

The results of the present study highlight the importance of staff for creating a context of social belongingness amongst the visitors at social day centres. Staff’s facilitation of communication amongst older service users has been described previously as important, and staff have a peripheral significance for older people as interactional partners [31,43]. Previous studies have demonstrated that at day centres, older people feel emotional support from the other older people there [24,45]. The findings of the present study indicate that staff at social day centres are key figures, both through their organisation of activities and by acting as people who show an interest in all the visitors. Thereby, they address visitors’ need to be part of a community and their need to be seen. This is in line with the staff’s own perception that they are facilitators at the social day centres as the need for belongingness is catered for by staff facilitating a friendly atmosphere and ensuring the older people have something to do together [31]. Hence, there is a difference compared to special housing and other institutions where due to a high workload the staff are task-oriented [46], whereas in our findings, staff were part of the group facilitating participation and activities.

Methodological considerations

The transferability of the findings of a qualitative content analysis is dependent on the selection of participants [36]. This study is based on interviews with 20 older people, recruited through convenience sampling [33], who visited different social day centres in the same municipality. This narrow recruitment of the sample could imply a skewed view of the studied phenomenon. However, the centres that the participants visited had different characteristics in the form of the number and frequency of activities offered, and some participants also visited other day centres in the municipality. Furthermore, the participants’ experiences and reasons for visiting social day centres differed, as did their demographics. Therefore, a certain variation of experience of the studied phenomenon can be said to be represented in the material. When using qualitative content analysis, variation in experiences for the studied phenomenon is crucial for a study’s credibility [36].

An important aspect of qualitative content analysis is the researchers’ pre-understanding, as it might have an influence both on the interview situation, and how the participants’ narratives are interpreted [36]. The interviews were conducted by three registered occupational therapists with previous experience of interviewing older people. Two were more experienced in conducting semi-structured interviews in their work than the third who had more experience of recording patients’ medical history. To compensate for this, the last author listened to the third interviewer’s first recording and gave constructive feedback on their conduct.

As described in the material and methods section, the analytical process has been a collective endeavour by all participating researchers, to avoid skewed findings. Even though the participating researchers are registered occupational therapists and engaged in research on older people, we have applied a variety of perspectives in our previous research (such as dementia studies, citizenship studies, intervention studies, welfare technology, fall prevention). Hence, alternative interpretations of the interviewees’ narratives have frequently been discussed in various stages of the analytical process, which decreases this study’s dependability on a single researcher’s pre-understanding [36].

Conclusion

The findings of the present study suggest that the social day centre is an important arena for creating a sense of context and belongingness amongst older people. Attendance at a day centre provides a daily structure where activities with other people – in a similar situation – take place. Furthermore, the findings suggest that staff have a significant role, not only to lead activities but also to help the older people to take on responsibility at the day centre and thereby feel needed by others. This study strengthens the knowledge regarding the importance of doing activities and being with others for health and well-being when ageing.

Acknowledgements

The authors thank the participants for their valuable contributions. We are also grateful for the contribution of Hanna Stagling (reg OT.) who conducted interviews for this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research received no external funding.