Loneliness in the general population: prevalence, determinants and relations to mental health

Social relationships and social integration are crucial for emotional fulfilment and development over the life span [1]. As social beings, humans have a basic “need to belong" e.g., [2]. Social isolation refers to a lack of social contact, which can be objectively quantified (e.g. living alone, without a partnership). Loneliness, however, is usually defined subjectively as a painfully experienced absence of social contact, belongingness, or a sense of isolation [3]. It refers to a perceived discrepancy between social needs and their availability in the environment [4]. Moreover, loneliness is an emotional state, reflecting the subjective experience of suffering from social isolation [5].

Research on loneliness over the life span concluded that loneliness was highest in late adolescence, gradually decreasing during middle adulthood, and then increasing for late adulthood [6, 7]. In the German Ageing Survey, men and women from 40 to 85 years participated in three waves from 1996 to 2008 in order to find out whether the extent of loneliness of adults in the second half of their lives has changed in Germany. The prevalence of lonely subjects was estimated at 3 to 7% and declined gradually with age, particularly in the oldest group (70-85 years;[8]). With regard to sociodemographic variables, loneliness has been linked to indicators of social integration such as romantic relationships, perceived social support and acceptance [9]. Unmarried individuals indicated feeling lonelier than married individuals [4]. Childlessness had no effect on loneliness in older adults [4]. Yet, living alone was not per se associated with loneliness, instead a smaller social network was an indicator of loneliness, both in men and women [10]. However, the significance of gender in experiencing loneliness is contested: In a study conducted by Tesch-Römer et al. [8] men reported more loneliness than women (from middle to late adulthood). In the KORA Age study which is based on a random sub-sample of a German community sample of over 4000 adults in the age range of 64-94 years from southern Germany, Zebhauser et al. [10] found that the mean level of loneliness did not differ between men and women; only in the oldest participants (>85 years) loneliness was higher in women. As a result, findings are somewhat difficult to integrate due to the heterogeneity of measures ranging from single items inquiring “if a person feels lonely…” to broadly used scales such as the original UCLA loneliness scale with 20 items [11] or the Loneliness scale by de Jong Gierveld and Van Tilburg [12] with 11 items.

Loneliness has been associated with many negative mental health outcomes [13, 14] such as depression, suicidality, reduced positive emotions, poor sleep quality and general health, as well as physiological changes (e.g., increased cortisol awakening response and pro-inflammatory gene expression). Additionally, loneliness was associated with depression, low life satisfaction, and low resilience - particularly in men [10]. It has therefore been considered a major source of psychological stress [15], especially when combined with depression [16]. Especially, the distinction of loneliness from depressive symptoms has been focused by Cacioppo and colleagues [17, 18]. Accordingly, the relation between loneliness and depressive symptoms are reciprocal, emphasizing that both constructs are intimately related but distinct.

Loneliness also aggravates the morbidity and mortality of cardiovascular, cerebrovascular, and other chronic diseases [15]. It has also been related to cognitive decline and Alzheimer’s disease in aging. In a recent meta-analysis, lack of functional and structural social integration predicted a 50% increase in mortality, which is comparable to traditional risk factors [19]. It has remained an issue of debate whether loneliness independently predicts mortality risk after adjusting for health status, health behavior, depression, and social isolation [20]. A recent meta-analysis of longitudinal data on 35,925 participants by Valtorta et al. [21] found a 29% increase for incident coronary heart disease and 32% for stroke in those with poor social relationships. This effect was in the range of other recognized psychosocial risk factors such as job strain. In the English Longitudinal Study of Ageing (ELSA), Shankar et al. [22] found that loneliness was associated with physical inactivity, smoking, and multiple health risk behaviors. In the Health and Retirement Study [23], the authors found that loneliness was significantly and positively associated with physician visits among persons aged 60 years and older. Three major pathways have been discussed by which loneliness affects health [21]: (1) Health risk behaviors such as smoking and physical inactivity, (2) defective immune function and increase of blood pressure, (3) psychological variables such as reduced self-esteem and decreased coping.

Notably, as most studies have used US samples and focused on late adulthood investigating health-related associations of loneliness [8, 10, 23], current prevalence data are limited for research on the link of loneliness to mental health beyond late adulthood for European populations, in particular in Germany. The purpose of this study was to determine prevalence and determinants of loneliness in men and women of the general population from 35 to 74 years and to identify associations with mental health, health behavior and health care utilization. Therefore, the purposes of the present study were (1) to assess the prevalence and determinants of different degrees of loneliness in men and women, and to determine its associations to (2) mental health, (3) health behavior and (4) health care utilization in a large German community sample across the age range from 35 to 74 years.

Table 1 compares participants with different degrees of loneliness based on sociodemographic features, health related variables, and distress. A total of 10.5% reported some degree of loneliness: 4.9% were slightly, 3.9% moderately and 1.7% severely distressed by feeling lonely. Overall, mean age of lonely participants was lower. Loneliness was more frequent in women, in participants without a partner or without children. Almost four times as many lonely participants lived alone compared to those without loneliness. SES declined with increasing loneliness. No significant increases were found for previous unemployment, although there was a descriptive trend of a positive link between feeling lonely and previous unemployment.

Concerning health behavior, the proportion of current smokers almost doubled with increasing loneliness. There was no association with BMI. The average alcohol consumption was negatively linked to loneliness. Regarding health care utilization, there were strong increases in the intake of anxiolytics and antidepressants among lonely participants. The majority of participants (63%) with a strong degree of loneliness had visited a physician (vs. 42% with no feelings of loneliness), and 21% (vs. 13%) had had inpatient treatments. Regarding mental health, more than half of the loneliest participants were also depressed (vs. 5% in the group with feelings of loneliness), and over 40% in this group reported anxiety and suicidal ideation (which increased from 6% to 42%) and 30% panic attacks in the past 4 weeks. Type D increased considerably with the degree of loneliness.

Figure 1 presents the proportions of (at least slightly) lonely participants across the age range, separately for men and for women living with or without a partner at the time the participants were interviewed.

Among those living with a partner, loneliness was much lower; few men (1.4 to 2.7%) reported feeling lonely, whereas more than twice as many women reported feeling lonely (up to 5.9%). In contrast, about 10-20% of the participants living alone indicated feeling lonely. Women living alone in the age range 35-44 years (20.7% vs. 13.9%) and 55-64 years (19.3% vs. 11.6%) were considerably more affected by loneliness than men. In the age range of 45-54 years (14.2% vs. 15.4%) and 65-74 years (10.7% vs. 10.6%), no significant gender differences were observed when participant lived alone. Among those living alone, the highest proportion of loneliness was found in the youngest group of women in the range from 35 to 44 years (20.7%), whereas men tended to report heightened loneliness in the range from 45 to 54 years (15.4%).

Table 2 shows significant predictors of distress - separately for depression, anxiety, and suicidal ideation. In addition to loneliness, age, gender, partnership, socioeconomic status, generalized anxiety, panic attacks, and depression were included as predictors in each regression model. Loneliness as one of the predictors of the first regression model almost doubled the likelihood of depression (OR = 1.91). As we expected, generalized anxiety and panic attacks were highly associated with depression, too. Additional factors contributing to a strong overall prediction (c = .90) were lower age and SES. Similarly, loneliness also positively predicted anxiety (OR = 1.21), in addition to lower age, SES, female gender, increased panic attacks, and depression. Prediction of suicidal ideation by loneliness was also substantial (OR = 1.35) in addition to higher age, lower SES, generalized anxiety, panic and depression (overall model, c = .87).

In a large community sample covering middle to late adulthood (35 to 74 years), we found that one in 10 (10.5%) participants reported some degree of loneliness. As in previous studies e.g. ([7, 8]), loneliness declined with age. Loneliness was more frequent in women, in participants without a partnership, without children and in those living alone. Socioeconomic status declined with increasing loneliness. Living alone was an important determinant of loneliness in men and women. However, the relationship between loneliness, gender and living alone appeared to be complex. Similar to previous findings [10] different patterns of loneliness were observed with regard to age and gender. On the one hand, younger women (below 45 years of age) living without a partner were more affected by loneliness than men. On the other hand, middle-aged men (between 45 and 64 years) were slightly more affected than women. Living without a partner had a stronger impact on younger women and middle-aged men. Finally, in the oldest age group from 65 to 74 years, loneliness declined and no longer differed between men and women living alone. Interestingly, when living with someone, loneliness was comparatively low. However, about twice as many women in partnerships (up to 5.9%) reported feeling lonely in comparison to men (1.4% to 2.7%). Additionally, our data show that living with a partner is linked to loneliness in almost all men and to a slightly lesser extent in women. It might alternatively reflect a reporting bias such as men are less likely to admit to being lonely [31].

Feeling lonely was associated with distress: More than half of the loneliest participants were also depressed (vs. 5% in the group without loneliness). Generalized anxiety, panic attacks and suicidality were strongly associated with loneliness, suicidal ideation increased dramatically from 6% to 42%. There was also a large increase of Type D behavior pattern. This may be due to the previously described relationship deficits in lonely persons and their tendency to experience negative affect [14]. Loneliness remained a clear predictor for depression [17], anxiety and suicidal ideation when we took into account demographic variables and other types of mental distress; odds ratios for depression were 1.9; for suicidal ideation and generalized anxiety, 1.35 and 1.21, respectively. I.e., there was still a 31% increase in suicidality when taking the major demographic and mental health predictors (depression and anxiety) into account. The association between loneliness and suicidality supports the theory [32] that thwarted belongingness and perceived burdensomeness are major determinants of suicidality (see also [33]).

Regarding health care behavior, the majority of participants (63%) with a strong degree of loneliness had visited a physician (vs. 42% without loneliness), and 21% had had inpatient treatments.

Overall, our findings support the view that loneliness poses significant health risks in terms of reduced mental health (depression, anxiety) and increased suicidal ideation [10, 21]. Loneliness also contributed to smoking as an indicator for an unhealthy lifestyle, but not to other risk factors such as alcohol use or diet (BMI). More physician visits, inpatient treatments, and intake of psychotropic medication may be due to subjects` reduced mental health. Taken together, these findings support the view that loneliness should be regarded and inquired about as a relevant health [14] variable on its own.

Strengths of this study reside in the large sample size and the use of standardized self-report instruments to measure distress. Interpretation of our findings is limited by the cross-sectional character of our study which does not permit causal conclusions. Loneliness may contribute to distress and suicidality, however, depressive and anxiety disorders may lead individuals to refrain from social contact out of inhibition and fear. This question of causality has been addressed for depression in a longitudinal study [17] indicating a reciprocal relationship. No similar studies are available for anxiety disorders, yet. As we did not directly assess the size and quality of social networks, we cannot estimate the effect of social isolation in our study which is a confounding variable when investigating loneliness. In line with previous findings [34, 35] our data suggests that younger age groups are more affected by loneliness. Thus, the investigation of the prevalence of loneliness and its impact on mental health in individuals under 35 years old would be desirable. While our findings may be taken as indicative for the validity of our measure of loneliness, we concede that we only used a single item to measure loneliness. The results of our study, which are overall in line with findings in research on loneliness using comprehensive questionnaires, indicate a first step of the external validity of a 1-item-measure of loneliness as reasonable alternative to loneliness scales, especially for large-scale surveys. Future studies will have to prove other aspects of validity of this measure by directly comparing it with other loneliness scales.

Our findings support the view that loneliness poses a significant health problem for a sizeable part of the population with increased risks in terms of distress (depression, anxiety), suicidal ideation, health behavior and health care utilization.