For the benefit assessment, 14 randomized controlled trials (RCTs) investigating interventions intended to prevent and treat social isolation and loneliness were analysed. Six studies focused on the evaluation of preventive interventions, while 8 studies investigated interventions with a therapeutic approach. Interventions implemented by volunteers or healthcare or social professionals existed both in the group of prevention studies and the group of therapeutic studies. The examined interventions are very heterogeneous: volunteer visits in private homes, telephone calls/friendships with volunteers, professional-led group programmes, technology training by volunteers, and a Tai Chi Qigong intervention in combination with volunteer health guides. The described interventions had a duration of 1.5 to 12 months. In the majority of studies, the mean age of the study population was between 70 and 80 years. In almost all studies, over 50% of the study population was female, and 1 study was even restricted to women only.

The risk of bias of all included studies was classified as high already at the study level.

None of the included studies investigated adverse effects of the intervention, but all other prespecified outcomes were reported. The number of investigated outcomes ranged from 1 to 16. Four studies reported no statistically significant changes in favour of the intervention for any of their observed outcomes. Two studies reported statistically significant differences in favour of the intervention for the sole investigated outcome. The remaining 8 studies present mixed results.

Out of a total of 10 statistically significant results found in the prevention studies, only 1 outcome was shown to have relevance. Findings are similar for therapeutic studies: out of 9 statistically significant results on different outcomes, 4 were shown to be relevant.

All things considered, the favourable results which were seen in some areas are difficult to interpret due to high risk of bias, unclear power of most studies included in the benefit assessment, and poor reporting quality of the evaluation of complex interventions. From the evidence available for the benefit assessment, no proof or indications can be derived of a certain type of intervention being effective for preventing, reducing, or managing social isolation and loneliness in elderly people. At the same time, however, it is impossible to conclusively determine the investigated interventions to be ineffective because hints of benefit can be derived for 2 types of interventions (volunteer visits in participants’ private homes and professional-led group programmes) and 5 outcomes (social support, mortality, anxiety, self-reported health status, and life satisfaction). For instance, hints were found for programmes involving volunteer visits to socially isolated and lonely persons at minimum increasing life satisfaction or reducing anxiety. Further, there is a hint of professional-led social group work increasing social support in persons at risk of isolation and loneliness. There are hints of professional-led group services reducing mortality and improving self-reported health in socially isolated, lonely persons.

The health economic assessment investigates (a) costs associated with the technology (intervention costs) and (b) comparative health economic studies. The systematic searches found only 2 health economic publications. These are from 2 studies with therapeutic intention which were also included in the benefit assessment. One study published a cost-utility analysis for the volunteer-implemented widow-to-widow programme, and the second performed a cost-cost comparison between the intervention and control groups for a professionally implemented psychosocial group intervention. The intervention costs calculated as part of study implementation amount to currency-converted and inflation-adjusted €574 per person for volunteer home visits. The difference in cost compared with the control group (standard care and information brochure) of currency-converted and inflation-adjusted €-218 was not statistically significant. For the professionally implemented psychosocial group intervention, there was a currency-converted and inflation-adjusted significant cost difference in the amount of €1127 in favour of the intervention group (control group: no intervention). However, this does not include the costs of the group programme reported in the publication, equalling currency-converted and inflation-adjusted €1053 per person. No cost-outcome ratio was determined for the measured outcomes.

Furthermore, when interpreting the health economic results, the different study types, methodological deficits, and the different underlying health systems with corresponding variation in the involved cost parameters must be taken into account. Therefore, no unequivocal conclusions can be drawn regarding the cost-effectiveness of certain forms of interventions for preventing or reducing social isolation and loneliness in elderly people, particularly not for the German healthcare context.

On the basis of the information provided in the 2 publications, the potential intervention costs were calculated for the German context. For volunteer visits (organization and implementation of 10 to 12 home visits per participant), they equalled €246 to €403 per participant, depending on whether supervision was involved. For the professional-led 3-month group programme, mean intervention costs of €434 per participant were calculated.

They were calculated in light of the results of the analyses from ethical, social, organizational, and legal perspectives are based on the systematic analysis of the discussion sections of the publications included in the benefit assessment, other relevant publications from the scoping literature searches, interviews of affected people, and the discussion in a stakeholder workshop. Interventions combating social isolation and loneliness are generally associated with positive connotations, with their “benefit” not necessarily being defined by health-related outcomes but contact with other people being perceived as a success in itself. Social contact is associated in particular with joy, fun, and higher quality of life, and favourable effects on health are expected as a result. The idea that services must be tailored to needs has been repeatedly emphasized. Needs orientation is related, on the one hand, to specific characteristics of the target group, such as reachability (e.g. “quiet elderly”), sociocultural makeup, special triggers of social isolation and loneliness (e.g. loss of close relatives), or disease-related barriers. Another topic area is the services’ contents. Different mechanisms of action have been discussed: community-building stimuli through group activities, the unburdening, connecting function of confiding in others, particularly people in similar situations, and the targeted reduction of individual psychological barriers and strengthening of self-efficacy in more therapy-oriented settings. Participation of the target group in developing services is believed to promote acceptance and ensure both the authenticity of encounters and fit of intervention content to interests. Otherwise, interventions may exhibit a high dropout rate, rendering them inefficient. On the other hand, differentiating between preventive and therapeutic interventions is deemed of little use, whereas focusing on the severity of impairment would be more useful.

The implementation of interventions must take into account both mental barriers and technical and organizational aspects. The removal of mental barriers can be supported, e.g. by multi-step services, where an initial trust-building phase is followed by a phase with more extensive contacts. Another essential factor in this context is the sustainability of services, which was identified as a critical ethical criterion. Technical and organizational aspects include the reachability of services by (public) transport or any driving services, taking into account any costs incurred, or low-threshold access to services without complex application procedures. Particular challenges result from the large regional variations in services (urban-rural gap), the population being heterogeneous in terms of sociocultural and socioeconomic background, and the difficulties associated with reaching particularly vulnerable population groups. Therefore, different strategies should be followed for the advertising of services. Alongside public communication via local media, bulletin boards, or flyers, which tend to attract the participation of relatively “active” seniors, interventions should employ targeted, if necessary, outreach strategies, e.g. involving general practitioners’ offices, mobile nursing or social services or pharmacies in order to reach more isolated clients who might be in particular need.

Further organizational aspects are infrastructure and staff. Group-based services might take place, e.g. in municipal or neighbourhood centres, elderly assistance facilities, day-care facilities for seniors, libraries, or sports facilities. Services to combat social isolation and loneliness are implemented by both trained professionals, e.g. social workers or nurses, and by volunteers who are typically laypersons with regard to their social work or nursing expertise. With support offerings which are based on reciprocity, members of the target group become active service providers as well. One challenge in this context is ensuring that all involved parties possess adequate qualifications, which are not limited to knowledge of the intervention itself, but also comprise skills such as discussion moderation, group leadership, social skills, and the handling of vulnerable groups. The recruitment and qualification of volunteers, in particular, can quickly become a hurdle to the implementation of interventions, particularly in regions which tend to be socioeconomically disadvantaged.

From a social law perspective, several options for integrating interventions to combat social isolation and loneliness are already available. Assistance for the elderly, for instance, already offers various interventions to combat social isolation and loneliness in the elderly, e.g. volunteer visiting services and professional-led group programmes. Preventive services may be covered by health insurance funds because social isolation and loneliness in the elderly increases the risk of disease, particularly mental disorders.

Suggestions for the future also include selective contracts as per Section 149a SGB V with long-term care insurance, municipalities, and welfare institutions, which also aim to better integrate the prevention of social isolation and loneliness in the elderly. It is also conceivable to enshrine care and case management in standard care under health insurance law as well as to enshrine a subjective public right to aid in case of social isolation and loneliness in elderly assistance law. This could provide affected people with legally enforceable rights to services even beyond the existing services. For this purpose, elderly assistance law would need to be restructured in such a way that it includes a catalogue of services listing favourably evaluated interventions. This could be modelled after health insurance law, whose concretization concept has implemented the very heterogeneous service prerequisites and service contents in a detailed and subjective legal manner.

Conclusion

In summary, the results of this HTA suggest a need for developing and testing valid and needs-adapted concepts for the prevention and reduction of social isolation and loneliness in elderly people on the basis of the variety of prior publications. The MRC framework for the development of complex interventions offers a framework for doing so. For the first step, the development of a theoretical impact model, prior research done in the studies analysed herein can be used, preferably from studies which found advantages of the intervention groups or hints of benefit at least in part of the observed outcomes. Participatory approaches involving relevant stakeholders are recommended for the modelling of interventions, taking into account affected people’s preferences and needs as well as service providers’ and volunteers’ skills and resources. The planning of the implementation strategy and subsequent feasibility study should be informed by requirements and challenges from ethical, social, organizational, and legal perspectives which were determined in Chapter 6 and should additionally comprise a realistic cost estimate which is valid for the German context. Ultimately, effectiveness must be verified in the context of an RCT which focuses equally on (a) process evaluation, (b) the determination of benefit and harm, including based on the outcome parameters determined in consultation with stakeholders, and (c) cost effectiveness. Transparent documentation of all steps ensures the traceability of the approach and the interpretation of results.