In the space of about fifteen years loneliness has been redescribed. What earlier generations treated as a sorrow of private life is now spoken of in the vocabulary of epidemiology: prevalence, exposure, risk, intervention. The World Health Organization has issued an advocacy brief on social isolation and loneliness among older people (WHO, 2021), and a consensus report in the United States has examined what health services could do about them (National Academies, 2020). Governments have followed with strategies and, in a few cases, ministers.

The redescription rests on strong evidence that the quality and quantity of a person's relationships are associated with how long that person lives. It has brought resources and seriousness to a neglected subject. This review does not dispute that evidence. Its concern is with what the public health frame brings into view and what it leaves in shadow, and with two bodies of scholarship, one sociological and one philosophical, that were writing about loneliness in old age long before it was called an epidemic and that are seldom cited in the policy literature.

The argument is that these traditions are not ornaments to the health account. They ask questions it cannot ask from within its own terms: what produces loneliness at the level of a society, whether loneliness and aloneness are the same thing, and what a lonely person might have a claim to. Later life is a good place to pose them, because it is where loss of partners and friends, retirement from work and the approach of death all press on the matter at once.

This is a narrative review of published work, selected for influence and for the clarity with which each source represents a position. It covers the principal reviews and reports of the health literature, sociological studies of old age and loneliness from the mid twentieth century onwards, historical studies of loneliness and solitude, and philosophical writing in the existential, phenomenological and analytic traditions. No systematic search was carried out and the selection leans towards work in English and towards Europe and North America. The review compares frames of understanding and does not pool findings.

The modern study of loneliness began in social psychology. Weiss (1973) separated emotional loneliness, the absence of a close attachment, from social loneliness, the absence of a wider circle, and held that one could not substitute for the other. Perlman and Peplau (1981) defined loneliness as the unpleasant experience that arises when a person's network of relationships is deficient, in number or in quality, relative to what that person wants. This cognitive definition is still the standard one. It makes loneliness subjective by construction and separates it from social isolation, which is an objective lack of contact (de Jong Gierveld, 1998).

Two developments turned a psychological construct into a health priority. The first was a biological account. Cacioppo and Patrick (2008) proposed that loneliness is an evolved aversive signal, comparable to hunger or pain, that prompts a social animal to repair its connections, and that when the signal persists it alters sleep, stress responses and the appraisal of other people. The second was quantitative synthesis. Holt-Lunstad et al. (2015) pooled prospective studies and reported that loneliness, social isolation and living alone were each associated with a higher risk of death. Findings of this kind permit comparison with familiar risk factors, and such comparisons have carried the subject into public debate.

From here the frame generates a programme: measure loneliness with validated scales, identify those at risk, and intervene. A meta-analysis of interventions found that the more successful ones addressed maladaptive patterns of social thinking instead of simply increasing opportunities for contact (Masi et al., 2011). The consensus report cited above was candid that the evidence for interventions deliverable through health care remained limited (National Academies, 2020). Table 1 places this frame beside the others discussed below.

Three limits follow from the frame's own logic. Because it treats loneliness as an exposure, it attends to the lonely individual and has little to say about the arrangements that made the individual lonely. Because it seeks reduction, it has no place for the thought that some loneliness is fitting, as grief is fitting after a death. And because its measures ask about a felt deficit, it cannot easily distinguish the person who is alone and content from the person who has adapted to deprivation by wanting less.

Sociologists of old age met loneliness early, and what they saw was social structure.

Philosophy contributes distinctions and arguments, and three of each bear on later life. Figure 1 sets them beside the sociological and public health contributions.

Placing the frames side by side suggests some practical corrections. Assessment should separate isolation, loneliness and chosen solitude, and should ask about loss, since bereavement calls for something different from a thin social network. Programmes aimed at individuals need to be weighed against measures that act on conditions: income in retirement, housing that allows people to remain near those they know, transport, and public places where casual contact occurs. And those who design services should allow that an older person may decline company without being a case of unmet need.

The gaps run in both directions. Health research would benefit from measures able to tell contented solitude from resigned adaptation. Sociological work has said little about very old people in institutions, who are usually excluded from surveys. Philosophical writing on loneliness has paid limited attention to dementia, where the capacity to keep oneself company, on which the idea of solitude depends, may be altered. Most of the literature in all three traditions comes from wealthy Western societies, and its categories may not travel unchanged.

The public health frame has made loneliness in later life visible and fundable, and its core finding, that social connection matters for survival, stands. Sociology shows that who becomes lonely depends on bereavement, resources and the place a society gives its old people, and that loneliness has a history. Philosophy shows that aloneness has a valuable form, that some loneliness may be inseparable from a long life, and that contact can be understood as something owed. An account that draws on all three would treat loneliness as a risk, a social fact and a human experience at the same time, and would be slower to assume that the remedy is always a service delivered to an individual.

To be declared by the author(s) before publication.

To be declared by the author(s) before publication.