Uncovering the impact of loneliness in ageing populations: a comprehensive scoping review

To illustrate the strategy and the results of the search, the study flowchart is presented (Fig. 1).

Table of Contents

Characteristics of the included studies

Among the 52 studies, 40 (76.6%) used quantitative methods (27 cross-sectional, 9 cohort studies, and 2 experimental, 2 longitudinal), 4 (16%) were qualitative, 3 (5.7%) were systematic or scoping reviews, and 4 (16%) applied mixed methods or opinion-based analyses, and 1 case report. Geographically, 20 (44,4%) studies were from Europe, 14 (31,1%) were from Asia, 6 (13,3%) were from the United States or Canada, 2 (4,4%) were from Latin America, and 3 (6,6%) were from regions such as Australia and Ghana. In total, 24 (54,4%) studies were conducted in community settings, followed by 8 (17,7%) virtual studies (including telephone interviews, online platforms, virtual support groups, mail, and WhatsApp), 4 (8,8%) in health care units, and 3 (6,6%) each in residential and institutional settings. Sample sizes varied from 7 to 35,878 participants, totalling over 150,000. Table 1 presents the detailed characteristics of the included studies.

Table 1 Characteristics of the studies

Of the 28 grey literature documents (Table 2), 15 were doctoral theses, followed by reports [3] and final academic projects [4]. The majority, 17 (51,8%), originated from Spain, with others from New Zealand, Oman, the US, the Netherlands and Canada.

The studies included in this review were conducted across a wide range of settings, as summarized in Table 1. These settings include community-based environments, where 24 studies were conducted, reflecting the increasing focus on understanding loneliness in everyday social contexts. Other settings include virtual environments (8 studies), which have gained significance, particularly in light of the COVID-19 pandemic, as more people have turned to online platforms for social interaction. Additionally, some studies were conducted in home-based settings, as well as in health care units and institutional settings such as nursing homes. The studies also varied in terms of sample sizes, ranging from small samples (7 participants) to large-scale studies involving over 35,000 participants.

The main sources of evidence on loneliness are diverse and include a range of study designs. The predominant method used in the dataset is a cross-sectional study, which explore the relationships between loneliness and various demographic or psychological factors. These studies, including those by Canjuga, Železnik, Neuberg, et al. (2018) and Liu (2022), provide valuable insights into how loneliness is associated with factors such as gender, age, health status, and social context. Cross-sectional studies are essential for identifying patterns and correlations that may inform interventions and further research. In addition to quantitative studies, qualitative research has also been crucial in exploring the subjective experiences of loneliness. For example, Aedo-Neira (2022) used qualitative methods to capture in-depth narratives from individuals experiencing loneliness, providing a valuable context for understanding how loneliness is felt and expressed. Scoping reviews, such as Tragantzopoulou and Giannouli (2021), are instrumental in synthesizing existing research, mapping the landscape of loneliness studies, and identifying research gaps.

Key concepts related to loneliness

Multiple studies distinguish between loneliness and social isolation. Specifically, loneliness, the emotional feeling of being disconnected or lacking meaningful social relationships, and social isolation, the objective measure of the absence of social interactions or connections, have been emphasized in various studies [35, 42, 44, 45], including the scoping review by Tragantzopoulou and Giannouli (2021).

Mental health and self-esteem are frequently examined in relation to loneliness, with studies such as Canjuga, Železnik, Bozicevic, et al. (2018) investigating how loneliness impacts mental well-being, including self-esteem. Scales such as the Rosenberg Self-Esteem Scale are commonly used to assess these variables. Research consistently shows that loneliness is associated with poorer mental health, including depression, anxiety, and lower self-esteem [41, 56,57,58, 67]. These effects are particularly evident in older adults, who may experience compounded psychological distress due to other life changes, such as retirement, health decline, or bereavement. The impact of loneliness on self-esteem is particularly noteworthy, as it often leads to a sense of worthlessness and further exacerbates feelings of isolation.

Figure 2 (social and relational dynamics) illustrates the key factors related to loneliness and social isolation, summarizing how individual characteristics, environmental and socioeconomic factors, and social and relational dynamics interact.

The emotional and social dimensions of loneliness are also key areas of focus. Studies distinguish between emotional loneliness, which refers to the absence of close, intimate relationships, and social loneliness, which is related to the lack of a broader social network [35, 50, 54, 65, 70]. These dimensions are often interlinked with emotions such as sadness, anxiety, and frustration. For example, Aedo-Neira (2022) highlighted the importance of these variables in understanding the subjective experiences of loneliness, especially in vulnerable groups such as elderly individuals. The emotional distress caused by loneliness can manifest in various ways, including heightened anxiety, depressive symptoms, and a sense of emotional emptiness [41, 56, 58, 66, 67, 69]. Such emotional outcomes are critical for qualitative studies that aim to capture the lived experiences of individuals who are lonely, as these emotional experiences are difficult to quantify but vital for understanding the personal impact of loneliness [65].

Personality traits and environmental factors are other crucial variables influencing loneliness and are represented as an individual characteristic in Fig. 2. Research by Liu (2022) and others underscores the role of personality in loneliness, finding that introverted individuals or those with a tendency towards social withdrawal are more likely to experience loneliness [32, 47, 49, 62]. Similarly, environmental factors such as living in rural versus urban areas or in residential versus community settings can affect the extent to which individuals feel socially connected [32, 47, 49, 62, 71]. For example, rural areas may lack the social infrastructure that facilitates regular social interactions, increasing the likelihood of social isolation. On the other hand, people living in urban environments may be surrounded by large numbers of people but still experience social loneliness if they lack close personal connections or feel disconnected from their social surroundings. The type of residential setting also plays a role, as those in institutional or health care settings may feel more isolated than those in community environments due to the lack of autonomy and personal relationships (environmental and socioeconomic factors. Figure 2).

Main consequences of social isolation and loneliness

The literature reviewed reveals a strong association between loneliness and social isolation and a range of physical health issues. Many studies link these conditions to an increased risk of cardiovascular disease, frailty, and a greater likelihood of developing chronic illnesses [23, 40, 46, 48, 57, 59, 72]. These physical health concerns are particularly prevalent in populations with limited social connections or those who experience higher levels of isolation. For example, as shown in Table 2, various studies highlight how the negative health impacts of loneliness and social isolation manifest in diverse forms, including cardiovascular issues and frailty, primarily among older adults and individuals in isolated settings. These conditions are exacerbated by prolonged isolation, underscoring the importance of social connections in maintaining physical health.

In addition to physical health, the mental health consequences of loneliness and social isolation are frequently reported in the studies included in this review. These include increased rates of depression, anxiety, sleep disorders, and cognitive decline [41, 57, 60, 69, 71, 72]. The data summarized in Table 3 suggest that loneliness often leads to a deterioration in mental well-being, particularly among older adults. Chronic loneliness can serve as a significant stressor, accelerating cognitive decline and increasing the likelihood of developing mental health disorders such as depression and anxiety. Studies consistently emphasize that the effects of loneliness are particularly pronounced in older populations, where social isolation exacerbates emotional distress and can contribute to the onset of conditions such as dementia.

The impact of loneliness extends beyond mental health, affecting overall well-being. Social isolation often leads to reduced social interactions, which subsequently lowers quality of life and diminishes social support [24, 32, 36, 41, 48, 58]. As shown in Table 3, the effects of isolation can lead to significant reductions in quality of life, where individuals experience greater loneliness and a sense of disconnection from others. This lack of social engagement further contributes to emotional and mental health issues, reinforcing the vicious cycle of loneliness. Without sufficient social interactions, individuals can experience increased feelings of helplessness and emotional distress, diminishing their overall quality of life.

An important aspect of this review was the exploration of gender differences in the effects of loneliness and social isolation. Some studies indicate that women are particularly vulnerable to the psychological effects of loneliness, reporting higher levels of depression and anxiety related to isolation compared to men [32, 35, 67, 69, 72]. This is consistent with the findings in Table 2, which indicate that women are more likely to report higher levels of mental distress associated with loneliness, especially in later life. This heightened vulnerability may be attributed to gendered social expectations, caregiving roles, and the greater emotional expressiveness often expected of women. On the other hand, men may experience different social impacts, such as the effects of retirement on loneliness [35, 40, 54, 68, 72]. As noted in Table 2, men often face challenges related to the loss of work-related social networks and changes in their roles postretirement, which can contribute to feelings of isolation.

Overall, the main consequences of social isolation and loneliness identified in the literature are far-reaching and affect both physical and mental health. As illustrated in Table 3, loneliness is linked to a range of health issues, including cardiovascular problems and frailty, as well as emotional health challenges such as depression, anxiety, and cognitive decline. The cyclical nature of loneliness reinforces its negative impact on health, leading to reduced social interactions and further deterioration in mental well-being. Additionally, gender differences must be considered, as women and men experience and respond to loneliness in different ways.

Furthermore, this scoping review also identified what is being studied in documents published in the “grey literature”. In general, these documents confirmed the findings established in scientific documents collected through the databases used in this investigation. These sources provided several key insights into the issue of loneliness and social isolation, complementing peer-reviewed studies.

First, many studies have emphasized the negative impact of loneliness on the mental, social, and physical health of older adults, with particular attention given to its effects on psychiatric patients [74]. These studies reinforced the finding that isolation exacerbates physical and mental health problems, especially for vulnerable groups.

Additionally, several grey literature documents noted that interventions to combat loneliness and isolation could be effective, particularly when tailored to social relationships, physical health, and mental well-being. These interventions are essential for improving the quality of life of those affected [75]. Another notable finding was the economic implications of addressing loneliness. Although interventions may have upfront costs, they also represent an opportunity for new business ventures focused [76] on providing services for those suffering from loneliness, such as social programs or elder care services.

Finally, some grey literature sources highlighted the need for further research to consolidate findings and improve interventions [77].

Table 3 Consequences of loneliness and social isolation

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