ORIGINAL RESEARCH published: 24 February 2021 doi: 10.3389/fpsyg.2021.627547 Meaning in Life: A Major Predictive Factor for Loneliness Comparable to Health Status and Social Connectedness Dídac Macià 1,2,3*, Gabriele Cattaneo 2,4 , Javier Solana 2,4 , José M. Tormos 2,4 , Alvaro Pascual-Leone 2,5,6 and David Bartrés-Faz 1,2 1 Departament de Medicina, Facultat de Medicina i Ciències de la Salut i Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain, 2 Oficina de Recerca i Innovació, Institut Guttmann, Institut Universitari de Neurorehabilitació adscrit a la UAB, Badalona, Spain, 3 Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut i Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain, 4 Departament de Medicina, Universitat Autónoma de Barcelona, Bellaterra, Spain, 5 Hinda and Arthur Marcus Institute for Aging Research and Deanna and Sidney Wolk Center for Memory Health, Edited by: Hebrew SeniorLife, Boston, MA, United States, 6 Department of Neurology, Harvard Medical School, Boston, MA, David Facal, United States University of Santiago de Compostela, Spain Objective: Loneliness is the subjective distress of feeling alone and has a strong impact Reviewed by: on wellbeing and health. In addition to well-known predictors like isolation and poor Ana Belén A. B. Navarro-Prados, University of Salamanca, Spain health, a better understanding of the psychological determinants of loneliness would Gema Pérez-Rojo, offer effective targets for future complementary interventions. CEU San Pablo University, Spain Tjalling Holwerda, Methods: In this cross-sectional observational study (N = 2,240), we compared Arkin, Netherlands the explanatory power of several important risk factors of loneliness with the *Correspondence: affective, motivational, and cognitive aspects of the Meaning in Life (MiL) construct. Dídac Macià didac.macia@ub.edu Different nested linear models were compared including socio-demographic, lifestyles, social-connectedness, and self-rated health variables, to assess the overlapping and Specialty section: non-overlapping explanatory power of each of them. This article was submitted to Health Psychology, Results: Health status and MiL were found to be the most important predictors of a section of the journal loneliness, followed by social connectedness and, with a much lower weight, lifestyles, Frontiers in Psychology and socio-demographic factors. Within the MiL factor, the most cognitive component, Received: 17 November 2020 Accepted: 20 January 2021 sense of coherence, had a greater explanatory power than the more affective and Published: 24 February 2021 motivational ones. Citation: Macià D, Cattaneo G, Solana J, Conclusion: Reduced MiL, the capacity of an individual to attach “value and Tormos JM, Pascual-Leone A and significance” to life, is a crucial predictor to the feeling of loneliness. These results Bartrés-Faz D (2021) Meaning in Life: suggest that programs aiming to combat loneliness should go well beyond situational A Major Predictive Factor for Loneliness Comparable to Health interventions and include more cognitive, value-centered interventions that enable Status and Social Connectedness. individuals to define and pursue a meaningful vital plan. Front. Psychol. 12:627547. doi: 10.3389/fpsyg.2021.627547 Keywords: loneliness, meaning in life, sense of coherence, mental health, social isolation Frontiers in Psychology | www.frontiersin.org 1 February 2021 | Volume 12 | Article 627547 Macià et al. Meaning in Life and Loneliness INTRODUCTION personality traits like low self-esteem, shyness, introversion, self- consciousness, resilience, or optimism (Perlman and Peplau, Loneliness is often defined as the feeling that one’s desired 1973). Recently, more cognitively based constructs have also quantity or quality of social connections is unfulfilled (Peplau been associated to loneliness: wisdom including personal and and Perlman, 1982; Hawkley and Cacioppo, 2010). Loneliness cultural values such as higher spirituality, compassion, or mastery is universal and may have evolved in our species as a signaling (Ben-Zur, 2018; Morlett Paredes et al., 2019). mechanism to change behavior and avoid dangerous isolation Here, we aimed to assess the contribution of meaning (Cacioppo and Patrick, 2008). However, loneliness is also in life (MiL), differentiating between its cognitive, affective, strongly subjective, involving a judgement of the meaning and and motivational subcomponents, to predicting loneliness adequacy of one’s social connections that necessarily presupposes and compared it to other well-known determinants an individual’s cognitive framework of values and expectations. (sociodemographic, lifestyle, health, and social connectedness). This is why similar social configurations (e.g., being single, The choice is motivated because it is the lack of “meaning” in having few friends, working alone, etc.) in different people, social interactions, more than number or frequency, that is often cultures, or even historical periods often give rise to very different pinpointed as the key determinant of loneliness. feelings of loneliness (Peplau and Perlman, 1982; Rokach et al., MiL is defined as the capacity of a person to attach value and 2001; Klinenberg, 2016; Snell, 2017). Thus, loneliness is distinct significance to his or her life (Steger, 2012). It was originally from “social connectedness” which refers to a more objective defined and assessed as a single construct (Steger et al., 2006), situational condition involving number, diversity, and frequency however, more recent studies have shown the idoneity of a of connections (De Jong Gierveld, 1998). In fact, distinguishing finer-grained partition into three subcomponents (Martela and between loneliness and social connectedness also makes sense Steger, 2016), which can be differently associated to relevant from a health perspective, since the causal pathways linking health outcomes (Bartrés-Faz et al., 2018): (1) A cognitive aspect, them to infirmity or higher mortality are partially independent coherence, capturing the ability of ‘understanding one’s life and (Rokach et al., 2001; Cacioppo et al., 2009; Shankar et al., 2011; the external world and how one fits in it‘, that we measured Boss et al., 2015). with the Sense of Coherence scale (SoC; Antonovsky, 1993). Over the past decades, the prevalence of loneliness has sky- Antonovsky defined SoC as a “global orientation that expresses rocketed (Snell, 2017) probably as the consequence of accelerated the extent to which one has a pervasive, enduring confidence profound changes in family structure, workplace relationships, of (a) comprehensibility, i.e., that the stimuli deriving from one’s digital connectedness, sedentarism, and urban social lifestyles, internal and external environments in the course of life are all of which affect not only the quantity and quality of social structured, predictable, and explicable; manageability (b) i.e., the interactions but also our values and expectations about them. resources are available to one to meet the demands posed by these Recent surveys report that between one and two out of every ten stimuli; and meaningfulness (c) i.e., these demands are challenges, adults often or always feel lonely in the US, Japan, and Europe worthy of investment and engagement.” Epidemiological and (D’Hombres et al., 2018; Dijulio et al., 2018). clinical investigations have provided convincing evidence that There is no longer a debate about the public health relevance higher SoC is associated with greater stress coping capacity and of high and persistent loneliness. Lonely people are more that it represents an important health-promoting resource, both likely to present health problems, including higher rates of regarding positive health perception (Eriksson and Lindström, depression and anxiety, cognitive impairment, and dementia, as 2006) and quality of life across all age ranges (Huang et al., 2017). well as poorer physical health, including motor dysfunctions, A strong SoC has been shown to predict subjective well-being hypertension, cardio- and cerebro-vascular diseases, obesity, and to a greater extent than physical disabilities in older individuals sleep problems (Cacioppo et al., 2002; Tabue Teguo et al., 2016; (Schneider et al., 2006) and be associated with reduced mortality, Sutin et al., 2018). Loneliness also increases the risk of unhealthy lower incidence of depression, and better cognitive function lifestyles like sedentarism, smoking, or substance abuse, which in (Read et al., 2005). Specifically, in the case of loneliness, for turn aggravate its deleterious load on health (Dyal and Valente, example, SoC was found to mediate the negative effects of 2015; Vancampfort et al., 2019). loneliness on feelings of hope amongst bereaved parents (Einav The growing interest of public health actors to combat and Margalit, 2020). loneliness has mainly focused on social connectedness, health (2) A motivational aspect, purpose, related to “long-term life status (especially mental health), and socio-economic variables goals, and aspirations that motivate behavior,” that we measured to define risk groups and intervention strategies. However, with the Purpose in life subscale (PiL; Ryff, 1995). PiL is less attention has been paid to potential cognitive and conceptualized as having a purposeful sense of direction, and psychological determinants whilst the International Loneliness related to “long-term life goals and aspirations that motivate and social Isolation research NetworK (I-LINK) has recently behavior.” PiL has been linked to a reduced risk of health emphasized “[loneliness] interventions must be tailored and threatening conditions such as stroke (Kim et al., 2013), matched to specific root causes of loneliness” (Fried et al., cardiovascular events, as well as with all-cause mortality (Cohen 2020). et al., 2016). PiL has also been associated to greater engagement However, studying the psychological determinants that, given in positive lifestyles such physical activity (Hooker and Masters, an individual’s social configuration, leads to loneliness has a 2016) and reduced sleep problems (Kim et al., 2015). In older long history. Researchers have pointed to numerous predisposing age, PiL is strongly related with mental and physical health, and Frontiers in Psychology | www.frontiersin.org 2 February 2021 | Volume 12 | Article 627547 Macià et al. Meaning in Life and Loneliness individuals with medium and high PiL levels exhibit lower health collected in the one year follow-up questionnaire. As for MiL care utilization and expenditures, showing higher social support subcomponents, we used specific questionnaires administered and resilience, and higher quality of life (Musich et al., 2018). at the end of the first wave (for more details, see Cattaneo Finally, PiL has been associated with better cognitive function in et al., 2020). A number of these questionnaires (e.g., loneliness, adults without dementia, and with reduced risk of dementia or MiL, and certain lifestyles) were not collected repeatedly in the mild cognitive impairment (Boyle et al., 2010). two waves, thus preventing a longitudinal approach. (2) All (3) Finally, a more affective aspect, significance, linked to respondents were free from neurological or psychiatric medical the idea of engagement, satisfaction, and fulfillment, that we diagnoses (148 participants had to be excluded from the 2,388 measured with the Engagement with life scale (EwL; Trompetter with completed questionnaires). The study was approved by et al., 2013). This MiL component relates to an individual’s the Comité d’Ètica i Investigació Clínica de la Unió Catalana evaluation of how valuable, worthwhile, and important life is. d’Hospitals and all participants gave their informed consent. Previous evidences showed that this dimension is associated with increased mental health by also promoting well-being and Data Collection Instruments reducing psychological distress (Ho et al., 2010), the risk of Loneliness depressive symptoms (Mascaro and Rosen, 2005), and the impact The main outcome variable of our study was estimated using the of depression in post-traumatic stress disorder patients (Owens Spanish version of the widely employed three-item UCLA scale, et al., 2009). This affective component is frequently targeted by adapted for large surveys (Hughes et al., 2004; Rico-Uribe et al., psychological therapies (Zhang et al., 2018) in order to identify 2016). It consists of three items in which participants have to meaningful values, promote behavioral changes in line with it, rate the frequency of several experiences (“How often do you promote mental health, and reduce depression (Trompetter et al., feel isolated from others?,” “How often do you feel excluded?,” 2013). and “How often do you feel that you lack company”) on a 3- Our interest in studying the contribution of MiL in point Likert scale (options: “1: Hardly ever,” “2: Some of the time,” feelings of loneliness lies in the fact that MiL components or “3: Often”). By summing up the score of each of the three are relatively modifiable and amenable to interventions and items, we obtained a quantitative scale ranging from 3 to 9. The education in values. In particular, cognitive-behavioral therapy- psychometric properties of the 3-Item UCLA Scale in our sample based approaches can focus on the identification of life values (mean = 3.76, sd = 1.20, alpha = 0.77) were comparable to the and the reinforced orientation of behavior toward them (Zhang ones obtained by Hughes et al. (2004) from a similar sample et al., 2018). Furthermore, MiL components (in particular SoC employed to validate their reduced scale. Following these authors, and PiL) have been related to a myriad of physical and mental we maintained the continuous quantitative nature of the additive conditions, including the ones frequently reported amongst final score treating it as an interval magnitude. lonely people such as anxiety, depression, cognitive or functional impairment with advanced age, and also risk for cerebro- Predictive Factors or cardio-vascular events (Eriksson and Lindström, 2006). We investigated potential predictive variables of loneliness Therefore, insights into the role of the affective, motivational, and grouped into five conceptually distinct groups: (1) socio- cognitive dimensions of MiL could suggest novel interventions to demographic, (2) lifestyles, (3) social connectedness, (4) general combat loneliness. health, and (5) meaning in life. Sample characteristics are provided in Table 1. Extensive references to the literature for METHODS every questionnaire and scale can be found in the published BBHI protocol (Cattaneo et al., 2018). Participants Study subjects were volunteer participants of the Barcelona Sociodemographic Brain Health Initiative (BBHI, www.bbhi.cat/en), a prospective (1) sex, (2) age, (3) level of education (primary, secondary, longitudinal cohort initiated in Barcelona (Spain) in 2017 and and higher), and (4) family income corrected by family size aimed to identify and characterize the lifestyle factors, biological and structure by normalizing the raw family income by the determinants, and their interactions, related to maintenance of corresponding poverty threshold given size and family structure mental and brain function across the lifespan (Cattaneo et al., according to the Statistical Institute of Catalonia (IDESCAT). 2018). Our study includes a subsample of 2,240 (mean age 54.3, standard deviation 7.3, range 40–68, 66.1% women) of the Lifestyles total BBHI registered participants (n = 5,100, mean age 53.4, (1) Nutrition was assessed using the Spanish version of the standard deviation 7.0, range 40–68, 66.7% women, using all Mediterranean Diet Adherence Scale (Schröder et al., 2011), registered participants as of February 2019). Inclusion criteria a 14-item (scoring 0 or 1) instrument that assess baseline obey the following rules: (1) Participants had completed all adherence to Mediterranean diet, where 12 questions ask of the necessary questionnaires regarding sociodemographic, about food consumption frequency (vegetables, tomato, rice, lifestyle, social connectedness, and health related variables pasta, nuts, sugar-sweetened beverages, etc.) and two questions (detailed below) through the dedicated BBHI web-based platform about food consumption habits (olive oil and chicken as (2,388 were selected). Socio-demographic, lifestyles, self-rated principal fat and meet source). (2) Exercise was measured health, social connectedness, and loneliness questionnaires were using the Spanish version of the International Physical Activity Frontiers in Psychology | www.frontiersin.org 3 February 2021 | Volume 12 | Article 627547 Macià et al. Meaning in Life and Loneliness TABLE 1 | Potential risk factors for loneliness included in the study with sample from the short Cognitive Reserve Scale (CRS) (Rami et al., characteristics. 2011) involving the training/information and hobbies spheres Predictors Sample characteristics of the Cognitive Reserve. These items directly ask about the degree of involvement in learning foreign languages, playing 1. Socio-demographic or listening to music, reading, writing, watching TV, painting, 1.1. Sex Female (66.1%), Male (33.9%) and other cognitively stimulating activities. (4) Sleep: The 1.2. Age 54.26 (sd = 7.15) Spanish adaptation of the Jenkins Sleep Evaluation Questionnaire 1.3. Level of Education Primary (3.5%), Secondary (23.1%), Higher (Jenkins et al., 1988; Pallarés-Sanmartín et al., 2019) was ed. (73.4%) used to assess sleep quality in the last month. The four 1.4.Family income corrected by 2.61 (sd = 1.15) items asking about sleep problems in falling asleep or staying family size and structure (times asleep, awakenings during the night and waking up tired above the corresponding poverty threshold) and worn out. 2. Lifestyles 2.1. Nutrition. Mediterranean Diet 8.20 (sd = 1.94) Social Connectedness Adherence screener (MeDAS) (1) Household Arrangement is a four-level factor specifying 2.2. Exercise. Physical Activity Low act. (18.8%), Moderate act. (42.4%), with whom a person lives (alone, with partner with or without Questionnaire (IPAQ) High act. (38.8%) children in charge, without partner but with children in charge 2.3. Cognitive Activity. Classical 13.56 (sd = 3.72) or other). (2) Social Interaction includes four out of the 12 proxies of cognitive stimulating items from the Spanish version of the LUBBEN Social Network activities Scale (Lubben, 1988; Vilar-Compte et al., 2018), two of which 2.4. Sleep Quality. Jenkins Sleep 8.02 (sd = 3.61) Evaluation Questionnaire (JSEQ) involve relatives, the other two involve friends: “How many 3. Social connectedness relatives/friends are you with or do you hear from, at least, 3.1. Household Arrangement Alone (15.8%), With partner (70.9%), Living once a month?,” “How often do you meet or hear from the without partner but with children in charge relative/friend you have the most contact with?.” The remaining (8.3%), Other (5.0%) eight questions were excluded because they contain clearly 3.2. Social Interaction. 4 question 13.94 (sd = 3.54) subjective appreciations of social isolation that conceptually from the LUBBEN Social Network overlap with our outcome variable. Scale (LSNS). 4. Self-rated general health 4.1. Cognitive Health. From 51.23 (sd = 8.04) Self-Rated General Health Neuro-QoL questionnaire, including (1) Mental Health was measured with the ultra-brief self- 12 questions on memory, attention, reported Patient Health Questionnaire (PHQ-4), consisting of and reasoning. two questions on depressive and two on anxiety symptoms 4.2. Mental Health. From the PHQ-4 14.1 (sd = 1.93) (Kroenke et al., 2009). The PHQ-4 Spanish version has questionnaire, consisting of 2 been found to have good psychometric properties and to be questions on depressive, 2 on anxiety symptoms. sensitive to treatment-related changes in a validation study 4.3. Physical Health. 3 questions 8.49 (sd = 1.28) (Mills et al., 2015). (2) Cognitive Health was measured with from the General Health PROMIS the Spanish version of the Neuro-QoL questionnaire (Correia questionnaire, of which 2 relate to et al., 2015). This is a 12-item questionnaire for self-perceived physical disability and 1 to physical memory, attention, and reasoning using a 5-point Likert well-being in general. scale. (3) Physical Health was measured using three questions 5. Meaning in life 66.24 (sd = 11.22) from the Spanish version of the General Health PROMIS 5.1. Sense of Coherence. questionnaire (Ader, 2007; Hahn et al., 2014), of which two Abbreviated version of the Orientation to Life Questionnaire (OLQ-13) relate to physical disability and one to physical well-being 5.2. Purpose in Life. Six-item 28.95 (sd = 5.7) in general. subscale of the Spanish version of Ryff’s Well-Being Scale Meaning in Life 5.3. Engagement with Life. 61.61 (sd = 9.18) (1) Sense of Coherence was measured using the abbreviated Trompetter’s scale (2013) to assess fulfillment and personal values version of the Orientation to Life Questionnaire (OLQ-13). This 13-item scale represents a short version of the 29-item original scale proposed by Antonovsky (1993) and has been Questionnaire (IPAQ; Román Viñas et al., 2013), a self- previously validated in the Spanish population (Virues-Ortega reported scale of physical activity by duration and frequency et al., 2017). (2) Purpose in Life was measured using the encompassing several domains (job-related, housework, leisure- subscale of the Spanish short version of the Ryff ’s Well-Being time, and others). Results are reported in three main levels Scale (Díaz et al., 2006). (3) Finally, Engagement with Life of physical activity: Low (inactive adults), Moderate, and was assessed with the Spanish translation of the 16 item- High. (3) Cognitive Activity was estimated using seven items Trompetter’s scale (2013). Frontiers in Psychology | www.frontiersin.org 4 February 2021 | Volume 12 | Article 627547 Macià et al. Meaning in Life and Loneliness DATA ANALYSIS of loneliness were low social connectedness and unhealthy lifestyles [R2 = 13.65%, CI (10.97%, 17%) and R2 = 8.09%, We modeled the explanatory contribution of each risk factor CI (5.88%, 11.09%), respectively]. Finally, socio-demographic to loneliness in a series of successive regression models using factors presented very modest contributions [R2 = 0.6%, CI ordinary least squares. This allowed us to clarify their adjusted (0.15%, 1.72%)], barely reaching significance (see Figure 1A for a (conditional on other risk factors being fixed) and unadjusted visual comparison and Table 2 for the corresponding R2 and Rp2 contributions. In particular, each potential risk factor was under different adjustments). associated with loneliness according to the following set of The predictive value of each factor was substantially reduced conditionings: (a) without controlling for any other predictive when we controlled for the other predictors. The total variance factor (this tends to be the option adopted in many public explained by general health became 5% [Rp2 = 7.37%, CI health and economic surveys), (b) controlling for risk factors (5.07%, 10.43%)] instead of 23.9% (non-adjusted). Similarly, the within the same conceptual group, (c) controlling for risk factors contribution of MiL to loneliness became 4.8% [Rp2 = 7.04%, CI belonging to other conceptual groups, and (d) controlling for all (4.87%, 9.67%)] instead of 25% (unadjusted). The contribution risk factors, both from within and without the same conceptual of social connectedness was reduced relatively less, only to one group. It is expected that the proportion of variance explained third, 5.9% [Rp2 = 8.54%, CI (6.39%, 11.4%)], indicating that by each predictor as we increasingly adjust for other risk factors its association with loneliness operates in a more independent will decrease (unless masking effects appear) owing to the high manner. On the other hand, the contribution of lifestyles nearly collinearity between some of them. disappeared, revealing that, under the supposition that there The explanatory contribution (goodness of fit) of each existed forward causal effects linking unhealthy lifestyles to predictor or group of predictors was assessed with the adjusted loneliness, these effects would be totally mediated or confounded coefficient of full (R2 ) or partial determination (Rp2 ), depending by the other risk factors. Further details on the particular on whether other controlling covariates were included in the contribution of each predictor within each conceptual group are model (see Table 2). We used the adjusted version of R2 and provided below. Rp2 to penalize for the loss of degrees of freedom and make models comparable to one another. By contrast, in our visual Socio-Demographic Factors representations (bar plots in Figure 1 and Venn diagrams in Socio-demographic factors presented a strikingly low predictive Figure 2), we did not plot adjusted R2 or Rp2 , but directly power overall. We found that lower family incomes were plotted percentages of variance to make sure that overlapping and associated with higher scores of loneliness, though the effect size non-overlapping areas added correctly. However, note that the was very small [R2 = 0.41, CI (0.02%, 1.2%)]. We did not find relationship between the proportion of total variance explained significant effects of sex, age, or education level on loneliness. by a set of regressors and their corresponding adjusted R2 is very close but not identical. The departure of the partial Rp2 Lifestyles can be still greater because this statistic is defined as the ratio of Except for nutrition, for which no significant association was the variance explained over the variance left unexplained by the found, all other lifestyles were able to predict loneliness in the adjusting regressors and not over the total variance. anticipated direction: people with healthier habits (more exercise, Some of our models include numerous covariates whose better cognitive activity, and more restful and sufficient hours mutual linear dependency was expected to be strong, but it is of sleep) were less likely to report high degrees of loneliness. precisely one of our main goals to assess the explanatory power Notably, the association with sleep quality was particularly strong of each of them as we hold the others constant (adding them [R2 = 6.68% CI (4.46%, 9.15%)], whilst exercise and cognitive as controlling variables). Further information on the collinearity activity, though significant, presented a much lower magnitude, between predictors can be found in the Supplementary Material not reaching 2% of the explained variance. It is worth noticing in the form of a cross-correlation plot and an estimation of the that these are full associations not controlling for any other risk Variance Inflation Factor (VIF) for each regression coefficient. factors. Upon adjusting for other risk factors, all these linear Because of a strongly skewed distribution of the error terms, dependencies vanished to non-significance. we estimated 95% confidence intervals (CI) for our statistics directly re-sampling the observations and treating risk factors Social Connectedness as random predictors (bootstrapping with R = 2,000 for each This group made of two factors was able to explain around model). The exact R code necessary to replicate all the statistical 14% of the total variance. Social interaction, measuring analyses and figures has been made publicly available (http://dx. frequency and number of close social interactions, had a doi.org/10.17632/zy39mdzxpg.2). slightly higher explanatory power [R2 = 7.89%, CI (5.52%, 10.38%)] than household arrangement [R2 = 5.74%, CI (3.89%, RESULTS 7.98%)]. Interestingly, the contributions of social interaction and household arrangement were largely independent from one Low self-rated general health and low MiL were found to another (see Figure 1). Regarding household arrangement, we be the most important factors associated with loneliness found higher values of loneliness in participants living alone [R2 = 23.8%, CI (19.9%, 28.06%) and R2 = 24.87%, CI [mean UCLA score = 4.28, CI (4.14, 4.43)] or living in mono- (21.62%, 28.45%), respectively]. Also, meaningful predictors parental households [mean = 4.06, CI (3.9, 4.24)], in comparison Frontiers in Psychology | www.frontiersin.org 5 February 2021 | Volume 12 | Article 627547 Macià et al. Meaning in Life and Loneliness TABLE 2 | Explanatory contribution for each risk factor in regression models with increasing number of adjusting factors. Adjusted by risk factors in other groups NO YES Adjusted by risk factors in the same group NO YES NO YES Df R2 (%) CI Rp2 (%) CI Rp2 (%) CI Rp2 (%) CI Socio-demographic 5 0.60 [0.15, 1.72]* - - 0.04 [-0.11, 0.88] - - Age 1 0.27 [−0.02, 0.91] 0.19 [−0.04, 0.77] −0.04 [−0.04, 0.17] −0.04 [−0.04, 0.2] Sex 1 0.13 [−0.04, 0.61] 0.06 [−0.04, 0.53] −0.04 [−0.04, 0.17] −0.04 [−0.04, 0.19] Education 2 −0.08 [−0.09, 0.28] −0.08 [−0.09, 0.26] 0.16 [−0.07, 0.78] 0.16 [−0.05, 0.77] Income 1 0.41 [0.02, 1.2]* 0.30 [−0.02, 0.99] −0.04 [−0.04, 0.23] −0.04 [−0.04, 0.19] Lifestyles 5 8.09 [5.88, 11.09]* – – 0.07 [−0.1, 0.96] – – Nutrition 1 0.44 [0.02, 1.19]* 0.04 [−0.04, 0.45] −0.01 [−0.04, 0.31] −0.02 [−0.04, 0.28] Cog. activity 1 0.71 [0.16, 1.58]* 0.35 [0, 0.98] 0.04 [−0.04, 0.46] 0.02 [−0.04, 0.42] Exercise 2 1.31 [0.52, 2.58]* 0.80 [0.21, 1.87]* 0.00 [−0.08, 0.53] 0.01 [−0.08, 0.56] Sleep 1 6.68 [4.46, 9.15]* 6.29 [4.19, 9.04]* 0.05 [−0.04, 0.51] 0.04 [−0.04, 0.53] Social connectedness 4 13.65 [10.97, 17]* – – 8.54 [6.39, 11.4]* – – Household structure 3 5.74 [3.89, 7.98]* 6.25 [4.16, 8.7]* 4.79 [3.01, 7.13]* 5.05 [3.29, 7.5]* Social Interaction 1 7.89 [5.52, 10.38]* 8.39 [6.06, 10.9]* 3.68 [2.02, 5.4]* 3.94 [2.33, 5.87]* General health 3 23.80 [19.9, 28.06]* – – 7.37 [5.07, 10.43]* – – Physical health 1 7.79 [5.62, 10.28]* 0.71 [0.13, 1.82]* 0.75 [0.11, 1.86]* 0.01 [−0.04, 0.45] Mental health 1 21.78 [18, 25.87]* 10.55 [7.59, 14.2]* 6.67 [4.4, 9.29]* 4.46 [2.63, 6.82]* Cognitive health 1 12.34 [9.29, 15.76]* 1.34 [0.46, 2.71]* 2.78 [1.32, 4.68]* 0.67 [0.06, 1.81]* Meaning in life 3 24.87 [21.62, 28.45]* – – 7.04 [4.87, 9.67]* – – Engagement with Life 1 14.30 [11.42, 17.63]* 0.24 [−0.04, 0.85] 3.38 [1.9, 5.19]* 0.07 [−0.04, 0.52] Purpose in life 1 17.21 [13.81, 20.58]* 0.94 [0.22, 2.06]* 4.32 [2.53, 6.49]* 0.31 [−0.03, 1.09] Sense of coherence 1 22.90 [19.52, 26.52]* 7.93 [5.65, 10.43]* 6.21 [4.15, 8.54]* 2.48 [1.28, 4.22]* All coefficients of determination are adjusted to take into account the loss of degrees of freedom associated to each risk factor and thus penalize overfit. Whenever other controlling risk factors are included (Models NO-YES, YES-NO, YES-YES), Rp2 corresponds to the coefficient of PARTIAL determination, that is Rp2 is constructed based on the ratio of the variance explained by one risk factor over variance left unexplained by the controlling risk factors. Percentile 95% confidence intervals (CI) were obtained bootstraping, R = 2,000, (*) indicating significant associations for which the bottom limit of the 95% CI must be positive. Rows in bold contain coefficients of determination for entire groups of predicting factors, indented rows (not bold) only for a single predicting factor. to individuals living with a partner with or without children in with loneliness strongly shrank after adjusting for the other risk charge [mean = 3.57, CI (3.52, 3.63)]. factor groups, owing to a large overlap with general health and social connectedness (see Figure 2, left). As to the particular Self-Rated General Health contribution of the three components in the MiL group, sense Both with and without adjusting for other risk factor groups, self- of coherence (SoC) clearly stood out above the other two, both rated general health occupies a comparatively predominant role. before and after controlling for the other risk factor groups The remarkable difference between adjusted and non-adjusted (see Figure 1 and related statistics in Table 1). Moreover, SoC contribution is mainly due to the presence of predictors from the almost completely accounted for all the contribution of the MiL group and, to a lesser extent, to the social connectedness other two components, the opposite not being true. In other group (see Venn diagram from Figure 2, left). Clearly, mental words, SoC, the most “cognitive” component of MiL, would still health is the main contributor within self-rated general health [R2 be considerably associated with loneliness even if participants = 21.78%, CI (18%, 25.87%)], well above cognitive and physical did not present differences in purpose in life or engagement health [R2 = 12.34%, CI (9.29%, 15.76%) and R2 = 7.79%, CI with life (see the overlapping pattern in the Venn diagram (5.62%, 10.28%) respectively]. Furthermore, when we partialed of Figure 2, right). out the three predictors by each other to test for independent contributions it was evident that only mental health retains a strong association [Rp2 = 10.55%, CI (7.59%, 14.2%)], in sharp DISCUSSION contrast with the very modest non-overlapping contributions of physical and cognitive health (see Table 2). In this cross-sectional study, we observed a strong relationship between low scores of meaning in life (MiL) in adulthood and Meaning in Life high feelings of loneliness. Its magnitude proved to be of the The explanatory contribution of MiL is comparable in effect same order as the other well-known risk factors for loneliness, size to that of general health. Likewise, the association of MiL namely general health and social connectedness. By contrast, Frontiers in Psychology | www.frontiersin.org 6 February 2021 | Volume 12 | Article 627547 Macià et al. Meaning in Life and Loneliness FIGURE 1 | Proportion of variability in loneliness explained by different risk factors in models with different number of controlling factors. The full model including all risk factors classified in five conceptually distinct groups (including 16 factors) was able to explain a total of 37.87% of the variability in loneliness levels [adjusted R2 = 37.31%, CI (34.40%, 41.75%)]. socio-demographic factors and lifestyles, with the exception of loneliness. However, studies investigating potential psychological sleep quality, were very little predictive of loneliness. determinants tend to be scarcer and are seldom conducted There are numerous observational studies and surveys in comparison with these and other major public health and establishing general health status, especially mental health and socio-demographic predictive factors. The strong relationship we poor social connectedness as the two key risk factors for found between loneliness and MiL, including the motivational Frontiers in Psychology | www.frontiersin.org 7 February 2021 | Volume 12 | Article 627547 Macià et al. Meaning in Life and Loneliness FIGURE 2 | Elliptical Venn diagrams with overlapping and non-overlapping areas proportional to the total variance in loneliness explained by each group of risk factors. Figures in parentheses correspond to the explained variance when we do not control for the other risk factors represented (total area of the ellipses). Figures without parentheses correspond to the variance when we control for them (non-overlapping areas of the ellipses). Socio-demographic factors have always been partialed out to account for sampling selection biases in our study. and cognitive underpins of this construct, suggests that particularly resilient, capable of maintaining themselves in a efforts to combat loneliness should include interventions state of health, despite enduring adverse situations, such as aiming at the consolidation of a structured meaningful poverty, marginality, or immigration (Antonovsky, 1990). SoC vital plan. was constructed to measure an individual’s belief that (1) inner In our study, additional models adjusting for predictors and outer stimuli are structured, predictable, and explicable; from within the same conceptual group (e.g., association with (2) resources are available to meet the demands posed by physical health holding mental health constant, etc.) were these stimuli; and (3) these demands are challenges, worthy also informative. For general health, we found that mental of investment. Hence, SoC is believed to strongly depend on health alone accounted for nearly all the dependency of the existence of values or principles that order and guide an loneliness with physical and cognitive health. By contrast, in the individual’s behavior and efforts. social connectedness group, household arrangement (those with Previous observational studies relating loneliness to whom we live) and social interactions (number and frequency psychological assessments similar to our MiL questionnaires have with family and friends) hold independent associations with generally collected and analyzed data favoring a causal direction loneliness. An interesting finding is that adults living with where loneliness is assumed to reduce a person’s meaning in life. children without a partner (mono-parental) are at a higher risk For instance, studies have asked people for their “sources” of of feeling lonely than those with a partner, in the same degree meaning in life and found personal relationships and family as as those living alone. This suggests that the key determinant of particularly crucial (Debats, 1999; Lambert et al., 2010). Indeed, loneliness regarding household arrangement might not be living manipulative psychological experiments have demonstrated alone but living without a partner. that conditioning feelings of social belonging can modulate our Regarding the MiL group, even though the three capacity to find worth and meaning in life (Stillman et al., 2009; subcomponents investigated were strongly linked to loneliness, Lambert et al., 2013). However, nothing precludes the opposite sense of coherence (SoC) was found to account for all the causal direction from existing, that is, meaning in life may variance related to the others: purpose in life and engagement protect us from loneliness (Stillman and Lambert, 2013). In that with life. This is a remarkable finding. SoC is the most cognitive sense, Rokach (2001) showed that one of the most important self- dimension of MiL, introduced by the health sociologist Aaron rated strategies for coping with loneliness (perceived causality) Antonovsky to explain why certain individuals seemed to be is “reflection and acceptance,” this strategy being particularly Frontiers in Psychology | www.frontiersin.org 8 February 2021 | Volume 12 | Article 627547 Macià et al. Meaning in Life and Loneliness helpful among older people (Rokach, 2001). After all, researchers believed SoC to remain stable after age 30 (Antonovsky, 1987) have often highlighted that it is not the lack of social connections and more recent studies have even found that SoC improves that leads to loneliness, but the lack of meaning in them. It could over time (Feldt et al., 2011). With this and the above results in then well be that the lack of meaning in our social bonds may mind, it is suitable to speculate that strategies to improve and arise or be aggravated by a lack of meaning in other spheres maintain MiL offer a strategically key target among the elderly of life, being difficult to efficiently intervene one ignoring in particular. the others. Our study has a number of limitations. First, the study We found very large overlaps in the variance of loneliness cohort is not entirely representative of the Catalan population. explained by health status, social connectedness, and MiL. These We have an overrepresentation of women (67 vs. 51% intricated statistical dependencies are indicative of complex in the Catalan population), of higher educated (73 vs. causal pathways (presence of confounding and mediated effects), 35%), and of higher income participants (a 24% higher that our observational data do not allow us to distinguish. average net income). Nonetheless, within our sample, loneliness Nor can we establish a forward causality direction linking low scores showed little statistical dependency with these socio- MiL to high loneliness. Consequently, and in the absence of demographic factors and our main results were not affected an established theory mechanistically linking them, we have when controlling for them, facilitating their generalizability to refrained from formulating any path analyses or structural other populations. equation model that would have favored one out of so many Second, our models assumed linear functional relationships potential causal pathways. Nevertheless, the striking strength between our loneliness scores and different quantitative variables of our correlational results, even after adjusting for the as we wished to capture first order main effects, whilst finer other predictors, strongly invite testing cognitive interventions details could have been captured with higher order expansions to combat loneliness that encompass reflection, reasoning, and interaction terms affording more flexibility but at a higher identification of personal values, and the comprehension of risk of overfit. Third, our observational analysis only contains individuals’ social and vital situation (e.g., acceptance and a snapshot of loneliness levels at a given point during a commitment therapy, mindfulness, etc.). If such programs person’s adulthood. Therefore, we were not able to distinguish were to succeed, they would have major implications for between chronic or transient loneliness, to which MiL may be the future management and prevention of loneliness as a differently associated. global condition. Finally, we did not evaluate the role of personality traits or Indeed, current governmental and other institutional specific medical conditions in modulating the relation between programs to combat loneliness mainly employ situational and MiL components and loneliness. Further studies may take these behavioral initiatives to re-wire socially isolated individuals, variables into account and explore their potential role as little train or re-train social skills, and address maladaptive social or non- modifiable confounders of the strong relationship we cognition (Young, 1982; McWhirter, 1990; Perese and Wolf, found between MiL and loneliness. If so, this would indeed limit 2005). However, previous studies and scientific meetings the extent to which interventions promoting MiL might impact have already stressed the limitations of focusing exclusively favorably on reducing loneliness. on promoting social contact and connectedness (Masi et al., In conclusion, our study emphasizes the relevance of 2011) and identifying risk groups based on health status and considering aspects of individuals’ psychological structure as socio-economic factors alone, not tailoring interventions to complementary determinants of loneliness, in addition to specific root causes (Fried et al., 2020). Our study provides well-known risk factors such as social connectedness and observational evidence for the importance of incorporating mental health. We also quantified the considerable overlap actions to challenge how a lonely person understands his or her between these cognitive psychological constructs and mental own life and obtains meaningful experiences from what he or health as predictors of loneliness. Further interventional she already possesses. studies and pilot programs are required to establish a From the viewpoint of aging studies, although we found no forward causality between improvements in Meaning in differences in the prevalence of loneliness across the limited age Life, especially cognitive scaffolds ensuring comprehension segment of our cohort (40–68) in line with numerous surveys (largely measured by SoC), and decreases in loneliness. If reporting a flat plateau in adulthood only limited at both ends successful, we will gain in the definition and promotion of by higher prevalence in adolescence and advanced age (Yang and an individual’s meaningful coherent vital plan a powerful Victor, 2011), public health studies and initiatives working on new weapon in the battle our modern societies are waging the impact of loneliness in elderly people should take notice of against loneliness. our results. During advanced age, key transitions linked with loneliness start accumulating, such as retirement from work, children leaving home, chronic health problems, bereavement, DATA AVAILABILITY STATEMENT or entry into long-term care. To adopt the classification used in our study, we can identify most of these risk factors as The datasets presented in this study can be found in online belonging to changes of either social connectedness or personal repositories. The names of the repository/repositories and health. By contrast, no negative changes from the meaning in accession number(s) can be found below: https://data.mendeley. life group seem to take place in old age. Indeed, Antonovsky com/datasets/zy39mdzxpg/2. Frontiers in Psychology | www.frontiersin.org 9 February 2021 | Volume 12 | Article 627547 Macià et al. Meaning in Life and Loneliness ETHICS STATEMENT FUNDING The studies involving human participants were reviewed The research leading to the reported results was funded by and approved by Comité d’Ètica i Investigació Clínica de grants from La Caixa Foundation (Grant agreement no. la Unió Catalana d’Hospitals. The patients/participants LCF/PR/PR16/11110004), Institut Guttmann, and Fundació provided their written informed consent to participate in Abertis. DB-F was funded by the Spanish Ministry of Science, this study. Innovation, Universities (RTI2018-095181-B-C21), and an ICREA Academia 2019 award research grants. JT was partly supported by Fundació Joan Ribas Araquistain_Fjra, AGAUR, AUTHOR CONTRIBUTIONS Agéncia de Gestió d’Ajuts Universitaris i de Recerca (2018 PROD 00172), Fundació la Marató de TV3 (201735.10). AP-L was partly AP-L, JT, and DB-F: securing funding sources. DM, GC, supported by the National Institutes of Health (R24AG06142 and JS: data collection. DM and GC: data analysis. DM and P01 AG031720). and GC: had full data access to all data in the study and took responsibility for the integrity of the data and SUPPLEMENTARY MATERIAL the analyses’ accuracy. DM and DB-F: drafting of the manuscript. DM, DB-F, AP-L, and GC: review and writing The Supplementary Material for this article can be found contribution. All authors: concept, design, critical revision, online at: https://www.frontiersin.org/articles/10.3389/fpsyg. and supervision. 2021.627547/full#supplementary-material REFERENCES Correia, H., Pérez, B., Arnold, B., Wong, A. W. K., Lai, J. S., Kallen, M., et al. (2015). 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