Abstract
While there is evidence that spouses can impact the self-management of adults with type 2 diabetes mellitus, less is known about the influence of the wider social network. This qualitative study explored the perceived impact of the family as well as friends and work colleagues on type 2 diabetes mellitus self-management. A total of 25 adults with type 2 diabetes mellitus participated in semi-structured interviews regarding their social experiences of living with diabetes. Deductive thematic analysis was applied to the data. Pre-existing themes of health-related social control and social support were identified in the wider social network, with additional themes of non-involvement and unintentional undermining also emerging.
Introduction
The prevalence of diabetes in Australia is estimated to triple during the years 2000–2025 (Magliano et al., 2008), an alarming rate of increase that is consistent with predictions across the world (Ginter and Simko, 2013; Whiting et al., 2011). This is largely due to the burgeoning of type 2 diabetes mellitus (T2DM), which is associated with the population ageing, and becoming more sedentary and overweight. The management of T2DM is complex and effortful, requiring the performance of a wide range of behavioural strategies on a daily basis, including checking blood glucose levels, taking medication, modifying food choices and engaging in regular physical activity (American Association of Diabetes Educators, 2008; Coyle et al., 2013). The costs of not systematically carrying out these self-care behaviours over the long term are serious, with eye disease, nerve damage and cardiovascular compromise among a host of potential medical complications (Gregg et al., 2014).
Living with a chronic illness is also known to have negative emotional consequences over the long term (Katon, 2011) and diabetes is no exception. Many people with T2DM experience elevated levels of depression and emotional distress that can, in turn, impact their self-management and have a negative impact on physical health outcomes (Beverly et al., 2012; Gonzalez et al., 2014). The combination of daily behavioural requirements and emotional consequences of the condition mean that the partner and family of the person with diabetes are inextricably drawn into the self-management process.
There is evidence that the social network can play a significant role in the persons’ emotional coping and self-management of T2DM (Martire and Franks, 2014; Miller and DiMatteo, 2013). For example, Glasgow and Toobert’s (1988) early study showed that family support was the strongest predictor of taking T2DM medications as recommended, and Trief et al. (2004) found that marital satisfaction was strongly associated with a number of self-care behaviours including prescribed exercise among T2DM patients. More recently, Johnson et al. (2014) used a structural equation modelling approach to demonstrate that use of a collaborative, problem-solving approach by couples living with T2DM is specifically associated with healthier eating by the person with T2DM.
However, while partners and family can have a positive influence upon self-management in people with T2DM, the data are equivocal. A number of studies have found that close relationships can also have a negative influence upon diabetes self-management (Henry et al., 2013; Rook et al., 2011; Utz et al., 2008). Past research has identified several different forms of problematic behavioural interaction, which in some senses form quite different ends of the behavioural spectrum. For example, spouses who do not have T2DM can explicitly undermine their partner’s dietary self-management by encouraging unhealthy eating (Henry et al., 2013) or compromise the person’s autonomy for self-management with excessive pressure and badgering about healthier behaviours (Rook et al., 2011). These negative spousal interaction effects have also been observed across cultures including in African American, Chinese American and Hispanic couples (Chesla et al., 2009; McEwen and Murdaugh, 2014; Utz et al., 2008).
Two common frameworks for understanding the ways in which a close social network can influence coping with a chronic illness are in terms of health-related social support behaviours (Miller and DiMatteo, 2013; Strom and Egede, 2012) and health-related social control behaviours (Martire et al., 2013; Stephens et al., 2010). Health-related social support refers to the provision of encouragement and positive feedback to those perceived to be coping effectively with their disorder (Sorkin et al., 2014). Conversely, health-related social control refers to attempts to correct or improve self-management, particularly in individuals perceived to be self-managing their illness sub-optimally (August et al., 2013; Lewis and Rook, 1999). Both domains encompass a range of behaviours that significant others may engage in, from expressing admiration for maintaining exercise plans, or preparing healthy meals (social support), to hiding cigarette packets, or monitoring what the person orders in a restaurant (social control). As noted by Sorkin et al. (2014), social control behaviour is conceptually different from undermining behaviour, as the latter refers to explicit attempts to subvert treatment recommendations – for example, encouraging a person with T2DM to eat inappropriate food (Henry et al., 2013). The bulk of the research in this area has concentrated on the social interactions of spouses (e.g. August et al., 2013; Khan et al., 2013; Stephens et al., 2013) or adult children (e.g. Sorkin et al., 2014). Relatively less is known about the influence of others in the wider social network, such as in-laws, friends and work colleagues, despite emerging evidence that these ‘close others’ can and do impact health outcomes (Martire and Franks, 2014).
This qualitative study therefore had a number of purposes. First, we were interested in learning how people with T2DM perceived the impact of their social networks, both the close network of spouse and immediate family as well as the wider network of friends, extended relations, work colleagues and neighbours, on their diabetes self-management and feelings about self-management. Second, we wanted to explore how adequately the health-related social control and social support models ‘fit’ with this wider social context.
Methods and methodology
Participants
Participants for this study were drawn from a larger study investigating the social experiences of Australians with diabetes (Browne et al., 2013). Adults with T2DM, aged 18 years and above who spoke English and who lived in the Australian state of Victoria, were eligible to take part. Participants were mainly recruited from the membership list of Diabetes Victoria (the peak consumer body and leading diabetes charity in this state). The study was also advertised in diabetes-related media and social media. To avoid bias, the study was promoted as a general exploration of the social experience of living with T2DM, with no specific reference to the impact of diabetes on relationships or family.
Following enquiry about the study, 108 study information sheets were emailed or mailed to prospective participants. Due to the level of interest in the study, purposive selection was used to ensure that the sample reflected a comprehensive age range, adequate gender balance and a combination of urban and regional dwellers. A total of 26 people took part in the interviews; however, one participant was subsequently excluded on the basis that he had not been formally diagnosed with T2DM, and because he showed evidence of cognitive impairment. Hence the final sample comprised 25 adults, 48 per cent (n = 12) of whom were women and 76 per cent (n = 19) were born in Australia. The median age was 61 years (range = 22–79), with 52 per cent (n = 13) currently working full or part-time. In terms of their clinical characteristics, the average duration of T2DM was 5 years (range = 0–29). A total of 20 per cent (n = 5) used insulin injections as their primary treatment strategy, 56 per cent (n = 14) used oral medications and 24 per cent (n = 4) managed their T2DM using lifestyle modification alone. All participants who took part in an interview received an AUD20 department store gift voucher as a token of appreciation for taking part.
Procedure
A semi-structured interview was developed in order to elicit participants’ narratives of their diabetes experience (Browne et al., 2013). For the purposes of this study, a series of open-ended questions were asked with specific reference to the participant’s immediate social network. Participants were asked to respond to questions in relation to three sets of relationships – their family (e.g. spouse, children, parents and siblings), friends and work colleagues (for those currently employed). The primary question was ‘What do your family/friends/work colleagues think or feel about your diabetes?’ This question was followed up by prompts designed to elicit greater detail and to improve the richness of the responses: (1) ‘What do they (family/friends/co-workers) think about your diabetes management?’ For example, diet, physical activity or medication taking; (2) ‘What do they (family/friends/co-workers) say or do that is encouraging or supportive?’ and (3) ‘What do they say or do that is discouraging or unsupportive?’
All interviews were carried out face-to-face, recorded and lasted an average of 55 minutes (range = 25–103 minutes). The audio recordings were transcribed verbatim and de-identified. After the transcripts were checked for accuracy against the audio, they were imported into NVivo V.10 to facilitate data coding, retrieval and analysis. Ethical approval for the study was granted by the Deakin University Human Research Ethics Committee.
Theoretical position and qualitative approach
A thematic analysis using a deductive (theory driven) approach was used to examine the data (Braun and Clarke, 2006). Thematic analysis adopts a phenomenological position to systematically identify themes, in this instance based on semantic content (the explicit meaning of the data) rather than latent content (the underlying meaning of the data). This approach was chosen because it facilitates the interpretation of identifiable themes for pre-determined, specific research questions. Two main themes – social control and social support – were pre-determined and the remainder were generated from the data. The five-stage method of data analysis follows that recommended by Braun and Clarke (2006).
Stage 1: Familiarisation
Two researchers (T.R.N.J. and A.D.V., both with postgraduate qualifications in psychology and experience in qualitative interviewing and research) each independently read and re-read the transcripts, and initial thoughts were noted. These initial impressions were then discussed with a view to identifying what was pertinent or significant to the research questions.
Stage 2: Generating themes
As previously noted, the broad themes of health-related social control and health-related social support (August et al., 2013) were used to guide the deductive thematic analysis process. Based on discussion, T.R.N.J. and A.D.V. agreed to transform social control and social support into specific themes, which formed the foundation of the coding framework. These two main themes devolved into four sub-themes (positive social control and negative social control; instrumental social support and emotional social support). A third main theme, ‘non-involvement’, which was based on initial coding, was also used. The data were further refined with the inclusion of an additional sub-theme (unintentional undermining).
Stage 3: Defining themes
Both researchers (T.R.N.J. and A.D.V.) collaboratively generated definitions for each theme. Having a clear definition facilitated accurate, replicable coding and also ensured the specific research questions were appropriately addressed.
Stage 4: Reviewing
All themes were reviewed to ensure they reflected the data. T.R.N.J. and A.D.V. coded the data independently and subsequently discussed their coding at length. Through discussion, any minor discrepancies were resolved, and they came to 100 per cent agreement on coding.
Stage 5: Reporting the findings
According to Braun and Clarke (2006), this stage offers the final opportunity to analyse the data. Quotes and compelling extract examples were selected to accurately reflect the final themes and illustrate the findings while relating back to the research questions. Information regarding the number of participants making reference to a theme, and also how many references to each theme were made, is given alongside the theme description.
Results
In total, four main themes were identified relating to the immediate social impacts and experiences of individuals with T2DM. Themes 1 and 2 were established a priori, whereas Themes 3 and 4 emerged from the data.
Theme 1: Diabetes-related social control
Health-related social control was included as an a priori theme based on previous work in this area (e.g. August et al., 2013). This main theme refers to the social network’s efforts to correct behaviour where the participant’s diabetes self-management is thought to be less than ideal. Our data suggested that the interpretation of the health-related social control response was variable and depended upon the participant’s perception of the intention of the behaviour. We determined that delineation into perceived positive and negative forms of social control was necessary.
Theme 1a: Perceived positive social control
The perceived positive social control response reflected the participant readily accepting, and often expressing appreciation for, the degree of influence over the diabetes management exerted by the social network. A total of 11 participants (44%) made 14 references to their experience of positive social control behaviours by their social network:
And he [husband] says to me ‘You need some food’ and I go ‘What? I’m fine’ - but actually he’s right. I need some food because usually I’ve gone a bit long. So he’s like a little weathervane to my mood. (54-year-old woman) Some of them [friends] are very, very good and quite often they will say to me ‘Shouldn’t you have had your insulin shot?’ and I say ‘I have’ … but they remind me. If I sleep in, in the morning sometimes on a Sunday morning someone will come around and visit me and say ‘Have you had your insulin shot?’ because it maybe 9 or 10 o’clock and I say ‘No, but I’ll do it before I eat’. But they’re solicitous and they’re aware of it and they’re encouraging. (67-year-old man)
Theme 1b: Perceived negative social control
By contrast, the perceived negative social control theme reflected the participant’s dissatisfaction with the social network’s attempts to correct their diabetes management. Rather than being helpful, here, the health-related social control behaviours are interpreted as critical or intrusive. Nine participants (36%) made 21 references to forms of negative social control, indicating a more frequently perceived response type than the positive version:
Mum says stuff (about diabetes) in a way that, she thinks she’s being supportive, and I really just wish she’d just drop it. (42-year-old woman) All my friends, they see something on television [and] they’ll tell me about it and I should be doing this and I should be doing that, I should be jogging. Well no, I don’t want to jog because it causes terrific impact on tendons and the feet and everything else. (60-year-old man)
Theme 2: Diabetes-related social support
Health-related social support provision was the other a priori theme included for evaluation based on previous research (Martire and Franks, 2014). In this instance, 13 participants (52%) reported 22 occurrences of their social network providing instrumental social support – defined as the provision of some form of practical assistance – to help them manage their diabetes. The distinction from health-related social control is that social support behaviours are not designed to correct suboptimal management but, rather, they aim to encourage or facilitate coping already perceived as being effective.
Theme 2a: Instrumental social support
Participants reported that their wider social networks provided practical assistance in a variety of different ways:
With our daughter she’s very good but she always says ‘would you like to come down for dinner tonight? We won’t have pasta, we’ll have a barbecue or we’ll have a grill or something and some salad’ and so on. I find that with a few exceptions, if I have pasta at night it’s just terrible for my blood sugars that night, they go up and they’re not right the next day either. So I just make sure that I don’t have it. So they’re very supportive, much more so now. I think they’ve learnt a bit from [the] process as well. (68-year-old woman) I’ve got a sister-in-law who’s bought, with her own money, several books to give me and they’re textbook-type prices. And you think ‘that’s very nice of you, thank you very much’. [She says] ‘I saw this and thought of you and there’s some good recipes in here’ and that sort of thing. (57-year-old man)
Theme 2b: Emotional social support
A second theme of socially supportive responses from the social network represented in the data was termed emotional social support (12 participants; 48%). These 16 responses differed from instrumental social support in that no practical support was being given, but here, the social network offers validation, understanding or acceptance. The first type of support was that of humour – making light of the diabetes in order to help the person feel more comfortable about their condition:
My girlfriends went ‘Geez, I hope I haven’t got that’ as they’re popping another cake and a glass of wine. They all ran and had blood tests. ‘We haven’t got that’ - back to the cakes! Very good, supportive, we’ve had plenty of laughs because we’re all getting to an age that we’ve all got different health issues. (60-year-old woman) And my kids joke ‘Here we go with the diabetes food’, and they just laugh but they eat it. (37-year-old woman)
The second type of emotional support involved the social networks sharing their own experiences of illness or treatment with the person with diabetes. This type of response serves a variety of potential functions, including normalising the diabetes experience, increasing intimacy through disclosure and offering solidarity:
But another friend who became diabetic when he was about 45, yeah, so maybe 15 years ago, he suddenly had this massively high blood sugar and he’s been on insulin ever since. And he soldiers up to me and says to me ‘How you going sugar?’, so that’s just sort of a thing between us. But most of the time people don’t talk about it much. (45-year-old woman) One of my friends has severe endometriosis on her bladder and intestines and everywhere, and she’s been told that if she wants to have a child she has to try in the next year or it’s not going to be good. She is my closest friend and so it’s more we talk about our health and ‘we’re a fine pair’ kind of thing. (59-year-old woman)
Theme 3: Non-involvement
The non-involvement theme was the most prevalent overall (16 participants; 64%) and most frequently endorsed overall (31 references), but encompassed two quite different interpretations of the same behavioural response. This theme broadly refers to members of the social network being aware of the participant’s diabetes but, from the participant’s perspective, deliberately choosing not to become involved in how the participant manages the condition. Data analysis further indicated two sub-themes within this broad category – positive non-involvement and negative non-involvement – with opposing emotional consequences for the person with diabetes.
Theme 3a: Positive non-involvement
The sub-theme of positive non-involvement (11 participants, 44%; 25 references) refers to the participant interpreting their social network’s lack of involvement in their diabetes self-management in an approving way. This sub-theme reflected the participant’s view that by not being involved in the day-to-day management of the illness, and not asking about it, their family members, friends or work colleagues were unaffected by it. The absence of diabetes impact was seen as indicative of the success with which the participant was self-managing their illness:
He [husband] doesn’t make a big issue of it, just let’s me do what I think is best for myself and I think I prefer it that way rather than having that constant reminder. (37-year-old woman) They [work colleagues] don’t talk lots about it because I actually think I manage it quite well now. (56-year-old man)
Theme 3b: Negative non-involvement
By contrast, the less commonly reported negative non-involvement sub-theme (5 participants; 20%; 7 references) speaks to the participant’s interpretation of their social network’s non-involvement as disinterest. This sub-theme encompasses statements in which the participant’s diabetes is perceived to be non-significant or unimportant to the social network, hence their lack of involvement:
Well they [friends] don’t know you’ve got it. You tell them every couple of years and [they say] ‘I never knew that’ and you know you’ve told them before. They really don’t know what the impact of that is. (59-year-old man) So, as far as the children are concerned, I think they just say ‘Oh, yes, mum has diabetes’ but they don’t see it as a problem, or they’ve never told me they have. No, I think I’d know, they’d be asking me questions about it. They never ask about it … They don’t see me having my blood taken in the morning, they don’t know how selective I am with what I’m eating and so it wouldn’t affect their lives. (54-year-old woman)
Theme 4: Unintentional undermining
The final theme, and the least frequently occurring response (4 participants (16%); 5 references), reflected the perception that the wider social network was undermining the participant’s efforts to self-manage or cope with the condition. These unsupportive interactions were considered to be unintentional and non-deliberate by participants (distinguishing this theme from the negative social control theme, which involves deliberate actions and commentary by the social network). Unintentional undermining refers essentially to thoughtless but insensitive behaviours/remarks from the social network, as perceived by the participant, which makes the process of managing diabetes more challenging:
My daughter has a business, she makes cupcakes, so she’s always forgetting and always bringing cupcakes around to the house. I’m telling her all the time ‘Learn to make them with sweetener and then I can eat them’ but she forgets. I suppose it’s like a lot of people, because it doesn’t affect them they don’t think about it. (42-year-old woman) Sometimes she’ll [mother] ring up and then she’ll start crying [saying] ‘I’m really worried about you. I don’t want you to die young’ and I know she means well, but it’s just not helpful. (35-year-old woman)
Discussion
This qualitative study is the first of its kind to investigate the social experience of living with T2DM with regard to the impact of the wider social network, and not just partners or immediate family members. In addition to exploring these broader social experiences, we sought to determine the applicability of health-related social control and health-related social support behaviours (Khan et al., 2013) to the extended social network. A thematic analysis approach was taken, allowing for the inclusion of a priori themes in the data evaluation process.
Our results were consistent with previous research findings in this area (Martire and Franks, 2014), whereby people with T2DM experience health-related social control and health-related social support responses from those in their social networks. Interestingly, the social control responses were not consistently perceived negatively. Whereas August et al. (2013) referred to social control behaviours by spouses as ‘implicitly or explicitly convey(ing) disappointment and anxiety’ (p. 713), potentially leading to resentment or resistance by a partner living with the chronic condition, our data did not show this consistently. There were certainly examples of participants finding the socially controlling behaviours of their family and friends unhelpful but there was also a substantial number of references to these behaviours being interpreted in a favourable way; at times, perceived as caring and thoughtful. Khan et al.’s (2013) quantitative study of spousal socially controlling behaviours found similarly contrasting effects on diabetes management. They suggested that the effects of social control behaviours are likely to be context specific, such that whether or not they impact positively or negatively depends upon a number of factors, including how much health-related social support has been provided by the spouse that day (Khan et al., 2013).
However, the social support and social control behaviour models did not account for all the data in our study, and two additional themes of non-involvement and intentional undermining were identified. Although a non-involvement response category has been identified in other research on dyadic adjustment in chronic illness (Newton-John and Williams, 2006), to our knowledge, this specific type of response has not previously been identified in the diabetes literature. Perhaps the closest comparable theme has been in Trief et al.’s (2003) qualitative study of couples coping with diabetes, which identified an ‘independence’ category. This category referred to the person’s preference for ‘managing certain aspects of the illness alone’ (p. 63), which is consistent with the positive non-involvement theme of this study. However, Trief and colleagues noted that independence was invariably associated with ‘tension and/or conflict’ in the relationship, because partners struggled to respect the individual’s desire for autonomous management of their diabetes and could not remain uninvolved. It is likely that the differences in theme between the studies are attributable to differences in study populations, as Trief et al.’s study participants were considerably younger (mean age = 49 vs 61 years), 45 per cent had type 1 diabetes and 88 per cent overall were using insulin to manage their diabetes. The younger age and more intensive treatment regimen of participants in Trief et al.’s study may mean that the social network felt less able to support the autonomy of the person with diabetes that is encompassed by the positive non-involvement theme.
The positive element of non-involvement was in terms of it being an endorsement of how successfully the person with T2DM was managing their health – the social network was not impacted upon in any way, hence had no need to be involved. Considering the research pointing to the stigma surrounding diabetes (Browne et al., 2013, 2014), the person’s desire for the condition to be ‘invisible’ to friends, work colleagues and wider family members makes sense. Conversely, perceiving the social network’s non-involvement as an undesirable response reflects the individual’s sense of being undervalued, in that their health was not perceived to be important or worthy of concern by others.
Rook et al. (2011) highlighted the importance of patient cognitions in determining the impact of a spouse’s socially controlling behaviours, and our broader social network data are entirely consistent with this emphasis. Whether or not socially controlling or non-involvement behaviours are seen as supportive or unsupportive of diabetes management will be attributable to the individual’s interpretations of the behaviours. However, variables such as marital quality or strength of friendship (Berg and Upchurch, 2007) are also likely to play a mediating role in this relationship, and are worth considering in future research endeavours.
The fact that the instrumental social support theme emerged from the data is not surprising, as previous research with families (albeit not the wider social network) has shown this to be a relatively common form of social interaction with T2DM individuals (Mayberry and Osborn, 2012; Miller and DiMatteo, 2013). The emotional social support theme that also emerged was broader, encompassing a range of interactions including humour and reciprocal self-disclosure of physical illness experiences by the social network member. Again, within the family context, humour has previously been identified as a helpful coping strategy for people with diabetes (White et al., 2007), but the benefits in relation to friends and work colleagues have not previously been recognised. The value of self-disclosure for diabetes management has been examined previously, but from the perspective of the younger person with diabetes sharing their disease experiences with parental figures (e.g. Osborn et al., 2013). Our data showed that adults with T2DM valued their friends and work colleagues sharing their own illness experiences too, suggesting a form of reciprocal self-disclosure known to promote intimacy and liking (Sprecher et al., 2013). Exploration of the factors that promote self-disclosure of illness experiences by ones’ social network, and whether that in turn prompts further self-disclosure by the person with T2DM – to the mutual benefit of both – would be of clinical interest in future research.
The final theme, unintentional undermining, has also been identified in previous diabetes research with patients and their partners (Henry et al., 2013), but the fact that this form of response also occurs in the context of the wider social network is concerning. Taken as a whole, the implications of this study suggest that for many people with T2DM, communication about their condition is less than ideal in terms of optimising self-management. The evidence is clear that diabetes management deteriorates when interpersonal relationships are non-cohesive (Miller and DiMatteo, 2013), and for a number of participants in this study, feeling unsupported by their social network in various ways (such as negative social control, experiencing negative non-involvement or being unintentionally undermined) was a reality. Primary care efforts to increase understanding of T2DM at the community level have been undertaken (Khunti et al., 2012), but our data suggest that education at the level of social networks themselves (e.g. work places, schools or sporting clubs) would be particularly valuable. Previous research in other chronic conditions has demonstrated benefits with work-based education programmes (obesity; McVey et al., 2013) and school-based interventions (asthma; Cicutto et al., 2014), so there are precedents for increasing health awareness among particular social groups. The fact that unsupportive responses were also frequently described during interactions with the spouse or partner suggests that promoting greater awareness of diabetes support within couples and family counselling services is important (Trief et al., 2006).
This study has several limitations. The fact that the sample was drawn from a consumer organisation may mean that these participants were more engaged in their diabetes care than the general population of adults with diabetes. The sample also comprised older adults, almost half of whom were retired. Whether or not their experiences reflect those of younger patients and/or those in the midst of their working lives is a question for further exploration. In terms of overall referencing of different members of the close social network, the spouse or adult partner was still the most frequently cited network member when discussing social impacts. We deliberately did not prompt participants to consider other members of their wider social network in their responses, in order to preserve the integrity of the data as a spontaneous and true reflection of their social experiences. However, future research in this area may develop this further by addressing only friends, work colleagues and extended family. Finally, although the purposive sampling procedure ensured variation in participant ages, gender and health histories, the sample was an entirely English-speaking cohort (albeit with 24% born overseas). As there is some evidence that non-English speaking Australians with T2DM have poorer diabetes health literacy (Bruce et al., 2003), it may also be the case that their interactions with their social networks are markedly different. Thus, our findings may not be generalisable and this, too, is an area for further investigation.
In summary, data from this study suggested that while immediate family members may have the most significant influence on diabetes self-management, friends and work colleagues also play a role. The health-related social control and health-related social support models were found to be applicable to this expanded set of social interactions. Non-involvement by members of the social network was also commonly perceived by people with T2DM, but this was not always interpreted negatively. A theme of unintentional undermining was identified which reflected an insensitivity or thoughtlessness by the social network towards the person with T2DM in their efforts to self-manage their condition. Collectively, these data suggest that increasing awareness of diabetes self-management is important not just within the family unit, but across all relevant social groupings.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship and/or publication of this article.
