Social relationships and survival in the older adult cohort*

Objective: to verify the influence of social relations on the survival of older adults living in southern Brazil. Method: a cohort study (2008 and 2016/17), conducted with 1,593 individuals aged 60 years old or over, in individual interviews. The outcomes of social relations and survival were verified by Multiple Correspondence Analysis, which guided the proposal of an explanatory matrix for social relations, the analysis of survival by Kaplan-Meier, and the multivariate analysis by Cox regression to verify the association between the independent variables. Results: follow-up was carried out with 82.5% (n=1,314), with 46.1% being followed up in 2016/17 (n=735) and 579 deaths (36.4%). The older adults who went out of their homes daily had a 39% reduction in mortality, and going to parties kept the protective effect of 17% for survival. The lower risk of death for women is modified when the older adults live in households with two or more people, in this case women have an 89% higher risk of death than men. Conclusion: strengthened social relationships play a mediating role in survival. The findings made it possible to verify the importance of going out of the house as a marker of protection for survival.


Introduction
Social relationships are interactions established by individuals throughout life, resulting from the broad set of political, economic, educational, occupational, cultural, and family systems. These social interactions promote the exchange of feelings capable of enhancing or mitigating the offer and receipt of assistance related to health maintenance (1)(2)(3) . The studies on social relationships use different terminologies to express conceptions, approaches, and cuttings of the theme, with emphasis on social support, networks, integration, and ties (1)(2)(4)(5)(6) .
Since Durkheim, at the end of the 19 th century, the effect of social relations on survival has been object of study (7) . There is diverse evidence of the need to understand the social interactions for the older adults, in high-income countries, starting in the 1950s of the 20 th century, with the emergence of classic theories about aging, due to their demographic relevance (2) .
The understanding of the influence of formal and informal social relationships on health conditions and mortality can be detailed by examining their structure and function aspects (2,(8)(9) . The structure assesses the quantity and type of relationships established, in the formal sphere, such as at work, in the use of the health services, and in participation in religious and cultural groups. In the informal sphere, the structure assesses the number and type of relationships in the family, such as with the spouse, children, and residents in the home. The function expresses the quality of the social relationships (formal and informal): whether positive or negative, whether satisfactory or conflicting, whether supportive or stressful (8) .
Diverse evidence signal the importance of relationships for quality of life in aging, being positive when frequent meetings take place and instrumental and emotional support is received (4,10) . Longitudinal studies (7) verified an increase in mortality among the older adults with little diversity or low frequency of contact with other people and decreasing levels of social integration (measured by a synthetic indicator that reflects ties with the spouse, close friends, and relatives and participation in religious and other types of groups).
In the older adult population, the risk of death is higher among men with less perceived social support (11) ; older adults who lived with other people had a lower risk of death than those who lived alone (12) .
Locomotion difficulties, older age, being male, poor self-rated health, pre-frailty or frailty were considered predictors of mortality among the older adults in studies conducted in Brazil (13) . In contrast, strengthening the social relationships can also minimize the effect of socioeconomic conditions on the health situation and mortality of the most vulnerable older adults (6) .
In the last 30 years there has been greater systematization of the theoretical and empirical bases of the causal impact of social relationships on health (9,14) . However, the mechanisms by which social relationships affect health have yet to be explored (5,10,15) . In this sense,

Method
This is a prospective cohort established between July and November 2008 (16) , with a representative The selection of the sample, in 2008, occurred based on the delimitation of the areas covered by all the fifteen primary health care services in the urban area, selecting with a systematic jump one in six households and interviewing all the older residents (16) .
Data collection for the monitoring occurred from the visit to the homes and the search of the participating residents. Those who changed residence were located in the new public places.
As it is a population-based study with residents in the community, in the constitution of the cohort, institutionalized older adults or those deprived of their liberty were excluded and, in the follow-up, the participants who passed to this condition were designated as losses. In both periods of data collection, www.eerp.usp.br/rlae 3 Soares MU, Facchini LA, Nedel FB, Wachs LS, Kessler M, Thumé E. the individuals who were not at their homes after three attempts were considered losses. Disabled older adults were interviewed with the help of a companion, with questions of self-perceived health not being applied to those who were unable to answer alone. The Multiple Correspondence Analysis (MCA) (17) guided the selection and grouping of variables and categories for the proposal of an explanatory matrix with less variability, with no harm to the grouped information.
The MCA has shown that "going out of the house", "going to parties" and "number of residents in the home", are indicators of the social relationships.
The independent variables were the following: gender (male/female); years of study (illiterate/ from 1 to 7 years/8 or more years); socioeconomic functional difficulty to perform basic activities of daily living (BADLs); needing help to perform one or more of the self-care activities: eating, bathing, grooming, dressing up, mobilizing, maintaining control over their eliminations (18) (Without difficulty/With difficulty); and multimorbidity -occurrence of two or more morbidities, which are: depression -Geriatric Depression Scale -GDS (19) , cognitive deficit -Mini-mental State (20) , high systemic blood pressure, diabetes mellitus, spinal problems, and rheumatic diseases -self-reported medical diagnosis (yes/no).
In the first analysis, an estimate of the median age Four possible interactions were tested: the first between smoking and multimorbidity, due to the fact that smoking is considered a risk factor for chronic noncommunicable diseases and mortality (11,22) ; the second between schooling and socioeconomic classification, www.eerp.usp.br/rlae 4 Rev. Latino-Am. Enfermagem 2021;29:e3395.
because the ways of organizing social groups are built as a survival strategy for individuals and can protect the poorest and least educated (1,6,14,23) ; the third tested interaction was between functional difficulty and going out of the house, in order to verify the effect on mortality of limitations for activities of daily living and of the difficulty in going out of the house (24)(25) ; and finally, the interaction between gender and the number of residents in the home, justified by the gender relations at this age, in which the social role of women as caregivers can be intensified (8) . The final model selected was considered to be a good fit as it did not refute the assumption of proportionality for the hazards, being significantly different from the null model and not different from the saturated model, at the 5% level.
The study was approved in its ethical aspects by the  During the follow-up period, practically half of the men and a third of the women died, with a difference in the median age between men and women of three years and five months old, with the mortality rate of men significantly higher than that of women.
The difference in the median between illiterates and those with 8 or more years of study was 2 years and 3 months. Low schooling significantly increased the mortality rate. At the end of the follow-up, the median age of death of the older adults belonging to the A/B (richest) economic classification was almost three years higher than that of the D/E (poorest) categories; the same occurred with the mortality rate of the poorest older adults being significantly higher than that of the richest. The older adults who, at the beginning of the follow-up, reported smoking and those who had multimorbidities, had a shorter survival time than those who did not smoke or did not have multimorbidities, but the difference in the rates was not statistically significant. The mortality rate for the older adults who live with more people is higher when compared to the other categories ( Table 1).
The survival of older adults without functional difficulties and of those who went out of their houses every day of the week at the beginning of the followup was about a decade longer than that of those with functional difficulties and of those who did not go out of their homes at all. The mortality rate was practically three times lower among those who went out of their houses every day and among those who did not have functional difficulties. The median age of death for the older adults who, at the beginning of the follow-up, reported going to parties was nearly four years higher than that of those who answered negatively to this question, with a significant difference in the mortality rate (Table 1). In the adjusted analysis, the risk of death was 57% lower for women, compared to men (p<0.001). However, this effect was modified by the number of residents in the home (p=0.03), and it was observed that, among older adults living in households with more than two people, women have an 89% higher risk for death than men (p=0.01) ( Although schooling and economic classification alone were not associated with survival at the 5% level, there is an interaction between the effects of both on survival. Thus, inferences cannot be made about the isolated effect of each variable, but about their interaction: among the older adults belonging to the C and/or D/E categories, being illiterate was a protective factor, reducing the risk for mortality by 75% and 64%, respectively, compared to those with higher schooling (Table 2). In the adjusted model, among smokers the risk of death was 48% higher than that observed in non-smokers (p<0.001). Among the older adults with functional difficulties for ADLs, the risk was 95% higher than in those who had preserved functional capacities ( Table 2). Going to parties maintained the protective effect, associated with a 17% reduction in the risk of death (p=0.02). After the adjustment, going out of the house continued to have an important protective effect on survival, with a 39% reduction in mortality in those who went out every day of the week (p<0.001) ( Table 2).

Discussion
The effect of social relationships on the survival of the older adults was the object of the study after eight years of monitoring the older adult cohort in Bagé, The article explored the functional and structural aspects of social relations (8)(9) and the survival analysis and affective well-being of the older adults, but also for their health conditions, preventing morbidities (26) and early hospitalization (27) .

The difference in mortality between men and
women showed greater female longevity, corroborating national and international longitudinal studies (11,28) . A study carried out in Viçosa, MG, with women aged 60 or over, showed that one of the positive aspects of female old age is the expansion of social participation, with the possibility of carrying out activities hitherto limited due to responsibilities with children and household chores (29) .
This explanation raised the hypothesis of an interaction between the gender of the older adult and the number of residents in the home.
However, the results showed that the effect of gender on survival can be modified by the number of residents in the home. For older adults living with two or more people, the risk of death was higher in women than in men. Brazilian women are living longer and with better living conditions due to the expansion of social security coverage, access to health services, and growth of the medical technology (30) . Family rearrangements resulting from the presence of chronic morbidities and functional difficulties may be necessary and, in the case of Brazil, in households headed by women the return of children and grandchildren to the home has been observed, when the nests are no longer empty and, although in low proportions, mothers and in-laws are also seen living in households headed by children (30) . Our results suggest that, in households with an older adult and two or more people, the older person is overburdened.
The expansion of the coverage of the Family Health Strategy (FHS) reduced hospitalizations for asthma, heart problems, and stroke, with a consequent decrease in mortality due to these conditions (31)(32) .  (14) . The social inequalities involved in determining health situations compromise equitable healthy aging; and access policies, health promotion strategies, disease prevention, and care for the older adults with chronic conditions can minimize the effects of inequality and promote health equity (35)(36)(37) . older adults who smoked compared to non-smokers (11) . The presence of intergenerational support and the support of the health networks are seen as fundamental for ensuring survival in old age, especially in low-income older adults (25) . In this perspective, it is necessary to discuss strategies for healthy, successful, and equitable aging. A qualitative research study carried out with older adults in the city of Rio de Janeiro identified that social participation, conviviality and interaction, support, and family contact, in addition to carrying out leisure activities and daily tasks with autonomy and independence, are practices that promote quality life (37) .
In our study, the MCA carried out before the survival analysis showed less explanatory power for the variables on the number of visits made than for going out of the house or going to parties. The association between the frequency of going out of the house and mortality in older adults with a focus on mobility was