Uzuki et al. BMC Public Health (2020) 20:1630 https://doi.org/10.1186/s12889-020-09752-9 RESEARCH ARTICLE Open Access Relationship between social support status and mortality in a community-based population: a prospective observational study (Yamagata study) Tsutomu Uzuki1,2, Tsuneo Konta2,3* , Ritsuko Saito1, Ri Sho2, Tsukasa Osaki2, Masayoshi Souri2, Masafumi Watanabe3, Kenichi Ishizawa3, Hidetoshi Yamashita3, Yoshiyuki Ueno3 and Takamasa Kayama3 Abstract Background: Social support, defined as the exchange of support in social relationships, plays a vital role in maintaining healthy behavior and mitigating the effects of stressors. This study investigated whether functional aspect of social support is related to 5-year mortality in health checkup participants. Methods: This study recruited 16,651 subjects (6797 males, 9854 females). Social support was evaluated using five- component questions: Do you have someone 1) whom you can consult when you are in trouble? 2) whom you can consult when your physical condition is not good? 3) who can help you with daily homework? 4) who can take you to hospital when you don’t feel well? and 5) who can take care of you when you are ill in bed? The association between the component of social support and all-cause and cardiovascular mortality was examined using Cox proportional hazard analysis. Results: The percentage of subjects without social support components was 7.7–15.0%. They were more likely to be male, non-elderly, and living alone. During the follow-up period, there were 166 all-cause and 38 cardiovascular deaths. Cox proportional analysis adjusted for confounders showed that only the lack of support for transportation to hospital was significantly associated with all-cause (hazard ratio [HR] 2.01, 95% confidence interval [CI] 1.26–3.05) and cardiovascular mortality (HR 3.30, 95% CI 1.41–6.87). These associations were stronger in males than females. Conclusion: This study showed that the lack of social support for transportation to the hospital was independently associated with all-cause and cardiovascular mortality in a community-based population. Keywords: Cohort, Mortality, Social support * Correspondence: [email protected] 2Department of Public Health and Hygiene, Yamagata University Graduate School of Medical Science, 2-2-2, Iida-Nishi, Yamagata 990-9585, Japan 3Global Center of Excellence Program Study Group, Yamagata University School of Medicine, Yamagata, Japan Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Uzuki et al. BMC Public Health (2020) 20:1630 Page 2 of 7 Background aspect - assessed its association with psychological status In recent years, the social determinants of health (SDH) such as depression [18–20], but not mortality. We hy- have attracted attention as an essential factor in the pro- pothesized that the functional aspects of social support motion of health and development of the disease. Social play a role in the determination of life prognosis. There- support/social networks, one of the components of SDH, fore, the present study examined the association between is defined as “support that is exchanged in social rela- the functional aspects of social support and all-cause tionships” and maintains healthy behaviors and mitigates and cardiovascular mortality in the Japanese population, the effects of stressors. However, the mechanisms by which have not often been examined before. which social support is associated with health status are The Yamagata study aims to prospectively examine not sufficiently clarified and are still controversial [1]. the association between genetic and environmental fac- One of the reasons for the difficulty of research on this tors and common diseases and life prognosis in local in- subject may be the variety of measures to evaluate social habitants. In the present study, we used data from the support and outcomes [1, 2]. Yamagata study to investigate whether social support is The Alameda study, a pioneering study on social sup- associated with all-cause and cardiovascular mortality in port/social networks, showed that social engagement a community-based population. with people is associated with mortality, together with appropriate health habits [3]. Since then, many studies Methods have reported that those who are socially isolated have Study subjects higher mortality than those with many social support/ The Yamagata study was conducted in seven cities (Ya- networks in various populations including African magata, Kaminoyama, Sakata, Tendo, Higashine, Sagae, American elderly women [4], local inhabitants in the and Yonezawa) in Yamagata prefecture, Japan, with the United States [5–7], Finland [8], and Brazil [9]. These re- support from the twenty-first Century Center of Excel- sults indicate that the association between social support lence (COE) program and the Global COE program. De- and mortality is commonly observed, irrespective of gen- tails of the Yamagata study have been described der, age, and ethnicity. Furthermore, some reports re- elsewhere [21]. This study’s target is the national health vealed the association between social support and insurance-covered local inhabitants that are mainly agri- cardiovascular disease [8, 10]. In Japan, several studies culture, forestry and fisheries workers, self-employed, have examined the relationship between various parame- part-time workers, retirees, and unemployed. The num- ters of social support/networks and life prognosis in the ber of potential subjects was 28,528 in this study. A total general population [11–14]. However, it has not been of 19,231 subjects aged 40 to 74 years provided written examined the association between social support and the informed consent to participate in the baseline survey of cause of death in detail. the Yamagata Study from 2009 to 2015. Of the 19,231 Lakey and Cohen argue that social support research who filled out the Yamagata study questionnaire, 2580 requires a theoretical perspective, and they raise the fol- subjects who had missing answers in social support lowing categories of theoretical perspectives: (1) stress components and essential clinical information, including and coping, (2) social constructionist perspective, and smoking, alcohol consumption, and medication, were ex- (3) relationship perspective [15]. Cohen also speculates cluded. The remaining 16,651 subjects (6797 males and on the involvement of psychological mediators and neu- 9854 females) were included in the final analysis of this roendocrine links to immune and cardiovascular func- study. The subjects have been followed from 2009 to the tion in how social support causes disease [16]. However, end of 2015. there are many properties in social support. Therefore, the study using different indicators may show different Baseline characteristics mechanisms or outcomes. A self-administered questionnaire was distributed to the Berkman et al. used an integrated approach to under- study participants at the specific health checkup site and stand how the structure and function of social relations returned by postal mail. When distributing the question- and networks influence health outcomes [17]. However, naire, we explained the outlines of the survey, including it is difficult to distinguish social support and social net- the voluntary nature of participation and the protection works clearly. In general, it seems that networks refer to of personal information, and then the participants gave the structural aspects of interpersonal relationships written informed consent. The Ethics Review Committee (such as the number of friends), while support refers to of the Faculty of the Medical Department of Yamagata the functional aspects (such as help from friends) [2]. University approved this study (approval No. 2018–464). Most previous studies focused on social networks, which This study was conducted based on the Declaration of reflect structural aspects. On the other hand, previous Helsinki. The baseline questionnaire gathered informa- Japanese studies on social support - the functional tion on social support using the following five questions Uzuki et al. BMC Public Health (2020) 20:1630 Page 3 of 7 because a previous study showed that these questions Results and answers were associated with depression in the Japa- Baseline characteristics of the 16,651 study subjects nese population [19]: Do you have someone 1) whom (6797 males, 9854 females) are described in Table 1. The you