Background
Loneliness and social isolation are international public health concerns that particularly affect the ageing society globally [
1]. Loneliness and social isolation are distinct but interrelated concepts. According to Valtorta and Hanratty [
2], one of the most widely used definitions of loneliness constitutes of social and emotional loneliness: loneliness is a subjective negative feeling associated with a perceived lack of a wider social network (social loneliness) or absence of a specific desired companion (emotional loneliness). There is much less consensus about the definition of social isolation however authors have approached it as a multidimensional concept, defining social isolation as the
objective lack or paucity of social contacts and interactions with family members, friends or the wider community [
2].
Loneliness and social isolation are risk factors for all-cause morbidity and mortality with outcomes comparable to other risk factors such as smoking, lack of exercise, obesity and high blood pressure [
3‐
5]. In addition, loneliness has been associated with decreased resistance to infection, cognitive decline and mental health conditions such as depression and dementia [
3]. Whilst every individual will experience loneliness at some point in their lives to a certain degree [
6], research has highlighted that older people are particularly vulnerable to experiencing loneliness and social isolation [
7,
8]. Approximately 50% of individuals aged over 60 are at risk of social isolation and one-third will experience some degree of loneliness later in life [
3]. Although loneliness and social isolation have been associated with a reduction in health status and therefore a decreased quality of life, findings suggest that both concepts may have independent impacts on health and therefore should be regarded as individual characteristics [
9]. However, there is also an overlap in the factors which contribute to loneliness and social isolation and sometimes authors use the terms interchangeably [
10,
11].
Risk factors for loneliness and social isolation among older people include: family dispersal, decreased mobility and income, loss of loved ones, and poor health. It is thought that societal change including reduced inter-generational living, greater geographical mobility and less cohesive communities have also contributed to higher levels of loneliness in the older population [
7,
12]. Due to advancements in public health and medical technologies, in addition to improved sanitation, the average life expectancy of the population aged 60 years or over has increased globally, resulting in a projected 56% growth in this population from 901 million to 1.4 billion by 2030 [
13]. Healthy life expectancy however still lags behind, and the increasing prevalence of loneliness contributes to this state of affairs [
14].
Given the increasing burden of loneliness and its impact on health and wellbeing, it is not surprising that there has been a growing academic literature, public and policy interest worldwide in loneliness and social isolation. For example, the Campaign to End Loneliness began in 2010 in the United Kingdom (UK) and aimed to create connections among older age people [
8]. In Denmark, a campaign titled ‘
Danmark spiser sammen’ which when translated in English means ‘Denmark eats together’ was established in 2015 as a popular movement against loneliness [
15]. The Australian Coalition to End Loneliness (ACEL), inspired by the Campaign to End Loneliness in the UK, was developed in Australia in 2016 and aimed to use evidence-based interventions and advocacy to increase awareness of, and address, loneliness and physical social isolation [
16]. ACEL did not clarify what was meant by the term ‘physical social isolation’ and this further highlights the varied terminology used regarding loneliness and social isolation. There are also growing campaigns in the Netherlands and New Zealand to tackle loneliness [
1]. ALONE, a national organisation in Ireland that offers support to older people, launched a Christmas campaign in 2018 called ‘Have a Laugh for Loneliness’ which encouraged families, friends and communities to get together during the winter in order to combat loneliness in their communities [
17].
Several reports about the range and types of loneliness interventions have been published globally. Within the United Kingdom, these have included reports by organisations such as Age UK [
18] and the Institute of Public Health in Ireland [
19]; guidelines by the National Institute for Clinical Excellence [
20]; reviews by the Social Care Institute for Excellence [
7,
21], and material collated by the Campaign to End Loneliness [
1]. The Canadian Counselling and Psychotherapy Association (CCPA) have published guidelines for addressing loneliness [
22]. Similarly, in the United States of America (USA), organisations such as Humana [
23], have published reports and a toolkit to overcome loneliness and social isolation, and the National Institute on Aging (National Institutes of Health) [
24] have published reports on improving the development of interventions to reduce loneliness and social isolation.
The report published by Age UK [
25] specifically highlighted the gap between evidence of what constitutes an effective ‘loneliness intervention’ in the academic literature and the practice of those delivering interventions. Nevertheless, service providers are experiencing increasing demand to provide initiatives to tackle loneliness, even in the absence of empirical evidence to fully support their innovations.
There are several published systematic reviews of loneliness and/or social isolation interventions, e.g. Cattan and White [
26], Cattan, et al. [
10] and Dickens, et al. [
9]. For example, Cattan and White [
26] critically reviewed the evidence of effectiveness of health promotion interventions targeting social isolation and loneliness among older people. It was reported that an effective intervention to combat social isolation and loneliness among older people tended to be long-term group activity aimed at a specific target group, with an element of participant control using a multi-faceted approach [
26]. Cattan, et al. [
10] conducted a systematic review to determine the effectiveness of health promotion interventions that targeted social isolation and loneliness among older people, and found educational and social activity interventions that target specific groups can alleviate social isolation and loneliness among older people. However, the effectiveness of home visiting and befriending schemes remains unclear [
10]. Similarly, a systematic review conducted by Dickens, et al. [
9] aimed to assess the effectiveness of interventions designed to alleviate social isolation and loneliness in older people. It was reported that common characteristics of effective interventions were those developed within the context of a theoretical basis, and those offering social activity and/or support within a group format. Interventions where older people were active participants also appeared more likely to be effective [
9].
Within this diverse literature, there are a range of frameworks used to categorise loneliness/social isolation interventions, often without clear definitions or rationale. Hence, there is a need to: map, organise and synthesise the large and diverse body of literature in this area; describe the range of intervention types; and to synthesise their content and characteristics.
Scoping reviews are useful for synthesising research evidence and are often used to categorise existing literature in a field. They can be used to map literature in terms of nature, features and volume; to clarify definitions and conceptual boundaries; and to identify research gaps and recommendations. They are particularly useful when a body of literature exhibits a large, complex or heterogeneous nature [
27].
Scoping review objectives
The objective of this scoping review is to map the large body of literature and to describe the range of interventions to reduce loneliness and social isolation among older adults. By focusing on existing reviews of loneliness/social isolation interventions, it aims to synthesise the ways in which interventions have been conceptualised and their components described.
Scoping review questions
How have authors of the reviews that were included in this paper (hereafter referred to as ‘review authors’) grouped or categorised loneliness and social isolation interventions?
How have review authors defined the terms used to categorise interventions?
How have review authors described their reasoning for categorising interventions in the format used?
Are there any similarities or differences in the terms used to categorise interventions across the reviews?
Discussion
The objective of this scoping review was to map the large body of literature and describe the range of interventions aimed at reducing loneliness and/or social isolation among older adults. By focusing on existing reviews of loneliness/social isolation interventions, it aimed to synthesise the ways in which interventions have been conceptualised and their components described.
There are various interpretations of loneliness and social isolation in the literature. Social isolation can be defined as ‘a state in which an individual lacks a sense of belonging socially, lacks engagement with others, and has a minimal number of social contacts which are deficient in fulfilling quality relationships’ [
59‐
62]. On the other hand, loneliness can be defined as a ‘subjective state based on a person’s emotional perception of the number and/or quality of social connections needed in comparison to what is being experienced at the time’ [
63,
64]. There is evidence to suggest that both concepts are distinct [
9,
65‐
67] as an individual can have a large number of social connections and still experience the subjective feeling of loneliness, or alternatively be objectively isolated but not experience loneliness [
68]. For some individuals, social isolation is a risk factor for loneliness [
18], and hence interventions designed to target social isolation may also alleviate loneliness. For other individuals, where the pathway to loneliness is not as a result of social isolation, such interventions are likely to have limited impact.
Although it is generally understood that loneliness and social isolation are distinct concepts, some review authors have stated that the terms are often used interchangeably [
10,
11,
46] or are conflated into a single construct [
68]. While there were fewer reviews identified that specifically focused on social isolation (
n = 4) compared to loneliness (
n = 11), there were no differences in terms of the countries where the research was conducted, the review type, or how the findings were reported. Distinguishing between the concepts of loneliness and social isolation is important when describing the goals of interventions and hence for specifying intervention characteristics that are relevant and effective in addressing each of these problems [
4]. This clarity is necessary if service providers are to use the accumulated evidence to choose interventions which are appropriate and effective relative to their service context and goals, for matching individuals to appropriate interventions, and for choosing appropriate outcome measures for evaluation. Rook [
44] made reference to the causes of loneliness and often linked these with the ‘goal’ of the interventions. Social inhibition or deficient social skills were linked to loneliness for some people and hence it was suggested that helping lonely individuals establish interpersonal ties might improve how they relate to others or provide new opportunities for them to have social contact. Alternatively, in circumstances where an individual was geographically isolated, an intervention which improves the social network may be more appropriate.
Review authors have used a range of terms to categorise the characteristics of interventions, such as mode of delivery, focus, nature, format, type and goal, but often with different meanings. Interventions were commonly categorised only by whether they were delivered to a group or to an individual. This is an important characteristic because group interventions are likely to be more appropriate for addressing social loneliness among individuals with insufficient social links [
69] than one-to-one interventions. However, it is only one of many intervention characteristics which may be directly, or via interaction with other characteristics, associated with intervention effectiveness.
Terms and terminology are important when undertaking research in the field of loneliness [
70]. Consistency in the definition of the terms and terminology increases accuracy, improves reporting, and aids in the replication of interventions across contexts [
71].
In some reviews, the underlying theoretical basis or rationale for the categorisation of interventions was not provided. Lack of theoretical underpinnings or explanations as to why interventions were categorised in a certain manner could lead to difficulty when attempting to distinguish in what context a particular category of intervention is most appropriate or effective. This reduces the value of the accumulated evidence base, since we are less able to identify candidate characteristics that may contribute to the effectiveness of interventions. Hence, there is a need for the development of a comprehensive framework that encompasses, defines, and elucidates all the key constructs identified in this scoping review. Without this framework, research to identify the effective mechanisms of loneliness interventions will be undermined by lack of clarity around intervention characteristics.
Interventions to reduce loneliness and/or social isolation are complex as they have several interacting components (e.g. goals, personnel, activities, resources and delivery mode), which may interact with features of the local context in which they are applied (e.g. age profile of participants, health status, environment such as housing, and cultural characteristics) [
72]. These characteristics need to be sufficiently described in order to allow use of the body of evidence to identify which characteristics (or combination of characteristics) are effective in a particular context and for which specific population.
The Template for Intervention Description and Replication (TIDieR) checklist and guide, published by Hoffmann, et al. [
73] was developed as an extension of the Consolidated Standards of Reporting Trials (CONSORT) 2010 statement [
74] and the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) 2013 statement [
75]. The TIDieR checklist provides a standardised template for authors to describe key elements for reporting of non-pharmacological interventions. The development of the checklist is associated with a wider movement towards standardising research reporting, demonstrated by the growing EQUATOR (Enhancing the QUAlity and Transparency Of health Research) network [
73]. The overarching purpose of the TIDieR checklist is to prompt authors to describe interventions sufficiently in order to allow their replication [
73].
The benefits of using the TIDieR framework is that it can be used for better description and reporting of interventions. This may lead to a more standardised reporting of intervention characteristics particularly in the primary literature, and therefore make synthesis of the literature more consistent. Additionally, it allows for comparison of key characteristics of interventions and for synthesis of interventions that share similar characteristics. The checklist makes it easier for authors to structure the accounts of their interventions/services; for editors to assess these descriptions; and for readers to use the information [
73]. However, although the TIDieR checklist may go some way towards assisting with the reporting of complex interventions, it might not be able to capture the full complexity of these interventions [
73] such as the interaction between different intervention components or their combined effect, the difficulty or complexity of behaviours/skills required either by those delivering or receiving the intervention; and also variability of outcomes [
76]. This is particularly relevant to loneliness/social isolation interventions which rely on more than one mechanism, therefore making it unclear which particular aspect of the intervention contributed most to its success or failure.
The heterogeneous nature of the interventions aimed at alleviating loneliness and/or social isolation among the older population; the settings where they are delivered e.g. care home or community; the group or one-to-one intervention delivery mode; and the population characteristics described in this scoping review, present a challenge for policy recommendations. The individuality of the experience of loneliness is also an important issue which has also been highlighted in the literature, as this may cause difficulty in the delivery of standardised interventions [
3]. There is no one-size-fits-all approach to loneliness interventions [
25,
70], and it is recommended that the assessment of individual needs should be conducted during the early phases of intervention, with subsequent tailoring of programmes to meet the needs of individuals [
77], specific groups or the degree and determinants of the individual’s loneliness. This includes sociodemographic factors i.e. age, poverty, being a carer; the social environment i.e. access to transport, driving status and place or resident; and physical or mental health [
2]. It is also essential to consider the needs of less well-researched groups such as individuals with physical disabilities, or ethnic minority groups, caregivers, recent immigrants, individuals with hearing and visual impairments, those who have been isolated for a long time, and older men [
78]. Several review authors have reported that the uptake of participants in the primary studies was heavily skewed towards the female population. This may be due to the reluctance of older men to engage with services and activities compared to women [
41]. Moreover, women also have a longer life expectancy across nations than men, and are more likely to participate in research studies [
37].
Systematic reviews are most appropriate for synthesising the findings of research that evaluates clinical treatments (simple interventions) [
79] and consequently base their estimates of effectiveness on one (or more) of the intervention characteristics, e.g. group or individual delivery settings. Complex interventions have several interconnecting parts and it is recognised that the evaluation of this type of interventions should go beyond the question of effectiveness to identify ‘mechanisms’ of action which can be described as the resources offered through an intervention and the way that people respond to those resources (for example, how do resources intersect with participant’s beliefs, reasoning, attitude, ideas and opportunities?) [
80,
81]. Hence, a realist review may be a more suitable approach to research synthesis when attempting to understand the mechanisms by which complex social interventions work (or not) in particular contexts [
62]. The realist review is a model of research synthesis that is designed to work with complex interventions or programmes and provides an
explanatory analysis aimed at discerning what works, for whom, in what circumstances, in what respects and how [
82]. This approach is more likely to result in findings that will help to identify and tailor interventions to fit the profile of the individual and their pathway to loneliness.
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