ABSTRACT

INTRODUCTION
It was estimated that lower respiratory infec- tious illnesses including pneumonia caused 1 080 958 deaths in older adults aged >70
Strengths and limitations of this study
▶ This is the first study to examine the associations between social capital and the PPSV23 vaccination among older adults aged ≥65 years after adjust¬ ing municipality-, community-,and individual-level effects. ▶ Almost 18000 people aged 65 years or older par- ticipated in a large, nationwide population-based study. ▶ While this study had a large sample size, the mea¬ surements were self-reported data. ▶ This study was cross-sectional study; therefore, we did not determine causal pathways. years worldwide in 2016. 1 Streptococcus pneumo- niae was the leading cause of morbidity and mortality of the illnesses globally, contrib- uting to 1189937 deaths, which were more than all other etiologies combined in 2016. 1 The adult pneumonia study group—Japan estimated that 69.4% of adult pneumonia was occurred in older adults aged ≥65 years annually in Japan and S. pneumoniae was the leading bacterial etiological agent as related to 53000  adult pneumonia cases in multi- centre prospective surveillance conducted from September 2011 to January 2013. 2 The 23-valent pneumococcal polysaccha- ride vaccination (PPSV23) and the 13-valent pneumococcal conjugate vaccine are effec- tive for preventing pneumonia caused by S. pneumoniae strains in older adults aged ≥65 years. 3 4 The following epidemiolog- ical determinants have been reported to be associated with coverage of the PPSV23 or the both vaccinations: age, 5 6 sex, 6 7 educa- tion, 8 income, 9 marital status, 8 house- hold structure,8 self-rated health,10 health literacy, 9 smoking, 6 general practitioner, 10 high-risk diseases for pneumonia including diabetes, heart diseases, chronic respiratory oo yd betselor។ Jseuß yd ÎSOS ,ÊS eunr no /moo ,jmd nedo(md//q)r/ mon bebsoluwo( .ÎSOS enul 71 no ESTEM-OSOS-neqo(md/GEN.01 se bersilduq feli :ne 1 diseases, 6 7 out-of-pocket amounts after subtracting the subsidy of municipalities from the vaccination costs. I  12 In Japan, the PPSV23 vaccination (PNEUMOVAX NP, MSD) has been incorporated into a national immunisa- tion programme for adults aged ≥65 years since October 2014. Public subsidies for the PPSV23 vaccination are available in most developed countries, including Japan. 13 In almost all the municipalities in Japan, PPSV23 vacci- nation payment is partly subsidised by the municipality and the remaining out-of-pocket cost is undertaken by the individual. 14 Recently, Naito and colleagues estimated that the 5years cumulative vaccination coverage was 49% across Japan in 2018 since the PPSV23 vaccination was started in 2014 as the national immunisation programme. 15 The immunisation programme is intended for older adults who aged ≥65 years, and those who aged 60–64 and have extremely restricted daily activity due to a disorder in their heart/kidney/respiratory function or immune function because of HIV infection. However, Murakami et al reported that there was the remarkable inequality in the PPSV23 vaccination rate (median, 5;95 percen- tiles of the vaccination rate: 41.8%, 13.6%, and 62.5%) in 1010 Japanese municipalities. 14 Murakami’s group also reported that the out-of-pocket cost and the number of direct mail notifications from a municipality were nega- tively and positively associated, respectively, with the municipality-level PPSV23 vaccination rate. 11 Murakami’s reports suggest that municipality-provided subsidies and implementations can improve the PPSV23 vaccination rate among the older adults at the municipality level 11 . However, municipalities may not be able to subsidize or implement the tools for encouraging the PPSV23 vaccina- tion depending on circumstances (e.g. financial reason). Therefore, it is important to pursue individual-level or community-level intervenable factors for improving the vaccination rate among older adults Social capital is one such factor that has undergone multilevel analyses to examine the contextual effects of group-level social capital in many studies in the field of public health 16–19 . A few reports show associations between individual-, group, or community-level social capital and paediatric vaccinations. 20 21 However, to the best of our knowledge, no study has yet assessed associa- tions between individual-, community-level social capital, and vaccination among older adults. Fostering social capital may improve the inequality in PSSV23 vaccination rate among older adults if social capital is related to the vaccination among them. We analysed associations between the individual and community-level social capital measures including civic participation (social participation), social cohesion (social tie) and reciprocity (mutual exchange of social support). The three social capital measures have been developed and validated as an instrument to measure community-level social capital based on data derived from older community dwellers in Japan. 17 Besides, the three measures at t the two-levels have been most frequently qoo yd betselo19 .jseug yd tS0S ,kS enut no \moo.jmd.neqo(md\/:q)ird monl bebso(nwoO .fS0S enut 71 no ES7E40-0S0S-neqo(md\6E11.01se betsilduq isnl) neq shown to be associated with health-related outcomes among Japanese older adults aged ≥65 years. 16 17 22-27 So, we evaluated whether the three measures of social capital were associated with the PPSV23 vaccination adjusting with municipality, community- and individuallevel effects among community-dwelling older adults aged ≥65 years.
METHODS
Study population This study had a cross-sectional design and used data from the Japan Gerontological Evaluation Study (JAGES). The JAGES was designed to describe the health status and social determinants of people who are physically and cognitively independent (not certified as needing long-term care). We used the 2016 wave of JAGES, a cross-sectional dataset obtained from self-reported questionnaires mailed to community-dwelling individuals in 39 municipalities. In the 2016 wave, 196, 438 of 279, 661 individuals (70.2%) responded to the survey. After excluding data from older adults who had been certified as needed the long-term care at t the survey, those who aged <65 years, and those who did not answer any question at all, the number of participants in the ‘JAGES2016’ data attributed to 180 021. The questionnaires comprised basic items and eight optional modules. We used data concerning the basic items that included questions about PPSV23 vacci- nation and three social capital measures. The data were nested in 631 communities essentially based on elemen- tary or junior high school district because a school district reflects a geographical scale wherein older Japanese people can move on foot or bike, 17 and the communities were further nested in the 39 municipalities.
PPSV23 vaccination
The outcome variable was the PPSV23 vaccination in the last 5years. This was assessed by asking the respondents, 'Did you get a pneumococcal vaccination in the last 5years? They chose from the following options: (1) no, (2) yes, I used my municipality’s subsidy and (3) Yes, but I did not use my municipality’s subsidy. We considered the no.2 and 3 as those who received the PPSV23 vaccination. Measurements of individual- and community-level social capital To assess community-level social capital, each response was aggregated to the elementary or junior high school distinct. These school districts can be interpreted as units at the community level for the following reasons: First, the district represents a geographical area wherein people can walk easily from home, interact with each other on a daily basis, and organise community activities. 17 Second, previous studies used the district as a unit for the commu- nity level to assess the effect of community-level social capital on health outcomes among community-dwelling older adults. 16 17 8 The value of the aggregated responses was scaled so that the effect of a one-unit increase or decrease can be interpreted as the effect of an 1 SD increase or decrease. oo Civic participation, social cohesion and reciprocity were evaluated as measurements of individual- and community-level social capital. 16 Civic participation was assessed as participation in the following five social groups: sports groups/clubs, volunteer groups, hobby activity groups, study/cultural groups and groups that conduct activities to teach skills/pass on experiences to others. Individual-level civic participation was scored ‘1’ if respondents participated in any of the five social groups once a month or more often and scored ‘0’ if respon- dents participated in these social groups less than once a month. Community-level civic participation was deter- mined by summing the participation proportions of the five social groups in each community. Social cohesion was assessed with the following questions: 'Do you think people living in your area can be trusted in general?’; ‘Do you think most people in your community aid others?’; and 'How strong is your attachment to your place of resi- dence?’. Individual-level social cohesion was scored ‘l’ if respondents answered ‘very’ or ‘moderately’ to at least one of the three questions and scored ‘0’ if respondents did not answer 'very' or 'moderately' to any of the ques- tions. Community-level social cohesion was determined by summing the proportions of those who answered ‘very’ or ‘moderately’ to the questions in each community. Reci- procity was assessed with questions related to emotional or instrumental social support as follows: 'Do you have someone who listens to your concerns and complaints?’; 'Do you listen to someone's concerns and complaints?' and ‘Do you have someone who looks after you when you are sick for a few days?’. Individual-level reciprocity was scored ‘1’ if respondents answered ‘any one or more’ to any of the questions and scored ‘0’ if respon- dents answered ‘nobody’ to all of the three questions. Community-level reciprocity was determined by summing the proportions of those who answered ‘any one or more’ to the questions in each community.
Covariates
Age was categorised into two groups: 65–74 years and ≥75 years. Educational attainment was categorised into five groups: <6 years (less than elementary school course completion), 6–9 years (elementary school course comple- tion to middle/completion of junior-high school), 10–12 years (junior high school completion to middle/comple- tion of high school), ≥13 years (middle/completion of university course, or more) and others that varied from these four categories. Equivalised income was calculated by standardising household gross income divided by the square root of the number of household members and was categorised into five groups: <¥0.5million, ¥0.50– ¥0.99 million,  ¥1.00–¥1.99 million,  ¥2.00–¥3.99 million and ≥¥4.00million. Marital status was classified into five groups: married, widowed, divorced, never married and others. Household structure was assessed by asking the respondents ‘Who do you live with?’. They were asked to choose from the following options: 'no one,' 'spouse,' ‘son,’ ‘daughter,’ ‘spouse of child,’ ‘grandchild,’ ‘brother or sister’, ‘father,’ ‘mother,’ ‘father-in-law,’ ‘mother-in-law’ and ‘the other’. The responses were categorised into six households: living alone, living with a spouse, living with offspring, living with a spouse and offspring, living in a three-generation household, and the others. The first five categorisations mirrored the five major households among adults aged ≥65 years in Japan. 29 The longest job that have ever had was assessed by asking the responders 'What is the type of the occupation that you have taken the longest in your life?' and they were asked to choose from the following options: professional/technical, managerial, clerical, sales/service, skilled labour, agricul- ture, forestry/fisheries, self-employment other than agri- culture/forestry/fisheries, the other, I have never had a job.
Statistical analyses
We created the Directed Acyclic Graph (DAG) to iden- tify a Minimal Sufficient Adjustment Sets (MSAS) of the potential confounders for estimating the total effects of social capital on the PSSV23 vaccination. We used an on-line tool, DAGitty V.3.0 (http://www.dagitty.net) to create the DAG. The DAG analysis revealed that the MSAS for estimating the effects were age, sex, education, income, marital status, household structure and munic- ipality (figure 1). The data consisting of the 180021 participants had missing in most of the characteristics including the PPSV23 vaccination, three social capitals, sex, educational attainment, equivalised income, marital status (online supplemental table 1). For handling the missing data, we performed multiple imputation (MI) among 180021 participants including the PSSV23 vacci- nation, the three social capital measures, and all the MSAS except for the community and municipality dummy variables, age, and household structure. There was no missing data in the age, household structure, and munic- ipality dummy variables. The community dummy variable had missing data, however, we did not impute the variable with the MI because the numbers for each community were assigned for convenience only, and there was no relationship between the numbers and the characteristics of the regions, and no regular distribution among them to enable MI. We generated five imputed datasets with MI by Chained Equations method. 30 To meet the assumption that data were missing at random and improve the quality of the imputed values, we included the longest jobs that have ever had and the community dummy variable as auxiliary variables associated with missing data and the PPSV23 vaccination. We confirmed that the two auxiliary variables did not bias on estimating the effects of social capital on the vaccination even if those were included in the estimation (figure 1). X  test was performed for categorical data. A multilevel Poisson regression model with a random intercept was used to calculate a coefficient and 95% CI as the effect of community- and individual-level social capital measure on the PPSV23 vaccination. Unadjusted coefficient and 95% CI were calculated in multivariate Poisson regression with a fixed qoo yd betsetor9 .jseug yd 1S0S ,ks enul no \moo {md.neqo(md\/:q)irt monl bebednwoO .fS0S enul 71 no ES7Ek0-OS0S-neqo(md\6E1f.01 se bersilduq teti :neq intercept and no covariate adjustment. Only the PPSV23 vaccination variable with quantitative variables after the MI was converted to a binary variable for the Poisson regres- sion analyses. The imputed values <1 were converted to 0, and 1 or more converted to 1. The other imputed variables were not converted for the regression analyses at all. Coef- ficients and 95% CI were adjusted with the MSAS and the auxiliary variables were also input in the model as the Stef. van Buuren’s recommendation.31 We estimated the effect to social capital on the PSSV23 vaccination from each imputed dataset with combining the results by using Rubin’s rules. 32 We performed a sensitivity analysis with the complete data set without missing data in the multilevel Poisson regression same as performed in the imputed data sets. All p values were two tailed and the significance was set at 5%. P values lower than 0.05 were considered statistically significant. We used Stata V.14.1 (Lightstone) for all analyses. Respondents were informed that participation was volun- tary and that returning the self-administered questionnaire would be deemed as consent to participate. Patient and public involvement No patients were involved in the development of the research question, study design, or data interpretation in this study.
RESULTS
Table 1 shows the individual- and community-level charac- teristics of the 180021 older adults who received PPSV23 vaccination and those who did not the vaccination with the MI data sets. A greater percentage of older adults who had individual-level civic participation, social cohesion or reci- procity received the vaccination compared with those without the social capitals. A greater percentage of older adults who had the rich (≥1 SD) of the community-level civic participa- tion or social cohesion received the vaccination compared with the standard (>–1SD, <+1SD) or poor (≤–1SD) of the two social capitals. A greater percentage of the older adults with the standard community-level reciprocity received the vaccination compared with the other two. A greater percentage of adults who were women, aged ≥75 years, had qoo yd betsetor9 .jseng yd 1S0S ,kS enni no \mos\fund.neqo(md\/:q)rt morl bebso(nwoO .fS0S enul 71 no ES7ER0-0S0S-neqo(md\9E11.01 se bersilduq fsil):neq Open access
qoo yd betbetor9 .jseug yd 1S0S ,kS enul no \mos.jmd.neqo(md/\qtri monl bebednwoO .fS0S enul Th no ESTEP0-OSOS-neqo(md/8E ht.01h se bersiduq izti :neqO
†SD of the five mutated data sets. ‡No imputed data because of no missing data. §The numbers were average of the five imputed data sets. PPSV23, 23-valent pneumococcal polysaccharide vaccination. higher education, lower equivalised income or widowed received the vaccination compared with those in the other categories. A greater percentage of older adults who lived in a three-generation household received the vaccination than those in the other household structures. A greater percentage of older adults who had ever had clerical or never had a job received the PPSV23 vaccination compared with those who had the other job. Table 2 shows the associations between individual-, community-level social capital and PPSV23 vaccination among the 137075 community-dwelling older adults after adjusting for all the MSAS and inputting the auxiliary vari- ables. The individual-level civic participation, social cohesion, or reciprocity was significantly associated with 13.0% (95% CI 11.0% to 14.9%), 5.0% (95% CI 2.4% to 7.6%) or 33.9% increase (95% CI 23.6% to 44.2%) of the PPSV23 vaccina- tion among the older adults, respectively. The rich (≥+1 SD) community-level civic participation was significantly associated with 3.4% increase (95% CI 0.02% to 6.78%) of the PPSV23 vaccination among the older adults, although the other two community-level social capital were not significantly associ- ated with the vaccination. We performed a sensitivity analysis with the complete data set and the results was almost same as the one with the imputed data set (online supplemental table 2). The both results showed that the three individual- level social capitals and community-level civic participation were significantly associated with the vaccination (table 2 and online supplemental table 2). At first glance, the estima- tions of community-level social participation in the imputed data sets and the complete data set look different as the poor (≤−1SD) community-level one was significantly associated with 4.6% decrease (95% CI −8.3% to −0.1%) of the PSSV23 vaccination in the complete data set (online supplemental table 2). However, the two estimates were consistent in that community-level social participation was significantly associ- ated with the vaccination.
DISCUSSION
Inequalities have been shown to exist between the PPSV23 vaccination rate among the older adults. 11 14 We analysed associations between individual-, community-level social capital and the PPSV23 vaccination among community- dwelling older adults aged ≥65 years. After adjusting for all the covariates and inputting the auxiliary variables in the imputed data sets, our analyses showed that one or more individual-level civic participation, social cohesion or reci- procity was significantly associated with a greater likelihood of vaccination among the older adults than those with the lack of these social capitals ( table 2 ). The rich community- level civic participation was associated with more vaccination than the standard or poor social capital among older adults ( table 2 ). These results suggest that older adults with the higher individual-level civic participation, social cohesion or reciprocity receive the PPSV23 vaccination greater than those without these social capitals, and that older adults living in districts with the rich community-level civic participation receive more vaccinations than those living in districts with the standard or poor community-level social capital. Several groups reported an association between municipality-provided subsidies and the PPSV23 vaccination as ecological studies at the municipality or nation level. 11 12 15 qoo yd betseto19 . Issug yd 1SOS , kS enul no \moo.\md.neqo(md\\:qtit\ mor\ bebed\nwoO .\SOS enul T1 no ESTER0-OSOS-neqo(md\BE11.01 es bedelidug 1stil :neq
group, sex, educational attainment, equivalised income, marital status, household structure and municipality) together with auxiliary variables (the longest jobs that have ever had and community dummy variable). The municipality and community dummy variables were included in the regression model as the random intercepts (municipality variable: level 3 and community variable: level 2). Unadjusted coefficient and 95% Cl were calculated in multivariate Poisson regression with a fixed intercept and no adjustment. We estimated the effect of social capital on the PSSV23 vaccination from each imputed dataset with combining the results by using Rubin's rules. The significant associations are shown in bold. *P<0.05; **p<0.01; ***p<0.001. MSAS, Minimal Sufficient Adjustment Sets; PPSV23, 23-Valent Pneumococcal polysaccharide Vaccination. In contrast, this study was conducted to assess the associations between social capital and the PPSV23 vaccination among Japanese adults aged ≥65 at individual, community and municipality-levels. After adjusting for all the covariates, the individual-level civic participation, social cohesion, reci- procity and community-level civic participation were signifi- cantly associated with the PPSV23 vaccination than in the lack of these social capitals ( table 2 ). Our results suggest that fostering individual- and community-level social capital may improve the inequality of the vaccination among older adults. Thereby, recommending a policy to mitigate the inequality of PPSV23 vaccination in municipalities among Japanese older adults. A few reports show associations between social capital and influenza vaccination among older adults. 33 34 However, these studies solely assessed associations between individual- level social capital and vaccination. Contrastingly, we assessed associations between multilevel (community and individual) social capital and PPSV23 vaccination among older adults (table 2). Our results suggest that both of the individual- and community-level social capitals were associated with the PPSV23 vaccination among older adults. Moreover, our study indicates the importance of such multilevel analyses. However, it is unclear why the three social capitals were asso- ciated with higher vaccination receipt, and how the three social capitals were associated with the PPSV23 vaccination among older adults. Future studies should address this issue. Nawa and Fujiwara recently reported associations between individual and community-level social cohesion and the second dose of measles vaccination among Japanese chil- dren. 20 Our results showed that the individual-level social cohesion but not community level's one was significantly asso- ciated with PPSV23 vaccination among older adults ( table 2 ). This suggests that the social cohesion had an effect on the two vaccinations similarly but at different levels. The present study has two strengths. First, to our best knowledge, this is the first study to show associations between the PPSV23 vaccination and individual- or community-level social capital among older adults aged 65 years, although there have been a few studies that showed associations between paediatric vaccinations, individual-, and community- level social capital, 20 21 or associations between influenza qoo yd betsetor9 .Jseug yd 150S ,kS enul no \moo.jmd.neqo(md\\:q);irri mon bebednwoO .150S enul Th no ESTEA0-0S0S-neqo(md%E11.01 es bedelidug teril :neq 7 :qoo yd betselor4 .1saug yd 1SOS ,kS ennt no \moo \md neqo\md\\:qlirl mort bebednwoO .1SOS enul Th no ESTERO-OSOS-neqo\md\GETh.Of se bedsiduq text :neq vaccination and only individual-level social capital among older adults. 33 34 Second, our result suggests that the indi- vidual- and community-level social capital may be one of intervenable factors which can ameliorate the inequality of the PPSV23 vaccination rates among a large population of community-dwelling older adults. There are some limitations to our study. First, we only anal- ysed the epidemiological association between social capital and PPSV23 vaccination among older adults; we did not determine causal pathways owing to cross-sectional nature of the data at the survey. Second, our findings cannot be gener- alised to people who had been certified as needed the long- term care because the participants were limited to those who were physically and cognitively independent. Third, a recall bias may have occurred in the survey for the PPSV23 vaccina- tion. The question asked participants the vaccination status in the last 5years, which they might not have remembered the vaccination if they had got it several years before the survey. The impact of this potential bias is unknown. Forth, we could not analyse the associations between individual- level, community-level social capital and the PSSV23 vacci- nation among the community-dwelling older adults who information of the school district was missing because we did not perform the MI for the community-dummy variable (see statistical analysis in the ‘Methods’ section).
CONCLUSION
Individual- and community-level intervenable factors are necessary to improve the inequality of the PPSV23 vaccination among older adults. We assessed associations between indi- vidual-, community-level social capitals and the PSSV23 vacci- nation among community-dwelling older adults aged ≥65 years. Our results show that civic participation, social cohesion or reciprocity at the individual level was associated with the vaccination, and that the rich civic participation at commu- nity level was associated with more vaccinations among older adults living in communities than those in communities with the standard or poor social capital. Our findings suggest that older adults with individual- or community-level social capi- tals receive more vaccinations than those without such social capitals. Therefore, fostering social capital is recommended as a policy to ameliorate the inequality of PPSV23 vaccination among older adults in Japanese municipalities. Author affiliations ¹Division of International Health, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan ²Department of Active Aging (donated by Tokamachi city, Niigata Japan), Niigata University Graduate School of Medical and Dental Sciences Biological Functions and Medical Control, Niigata, Japan 3Department of Social Preventive Medical Sciences, Center for Preventive Medical Sciences, Chiba University, Chiba, Japan 4Department of Gerontology and Evaluation Study, Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan Acknowledgements We deeply appreciate all the participants of the survey. We thank the other members of the JAGES project for their constructive suggestions for this manuscript. This work was supported by the Japan Science and Technology Agency-Supported Programme on Open Innovation Platform with Enterprises, Research Institute and Academia (grant number JPMJOP1831; development issue number five). We would like to thank Editage (www.editage.com) for English language editing. Contributors KIS had the idea for the study, performed the statistical analysis and drafted the manuscript as the principal author. YS designed the questionnaires to ask respondents the PPSV23 vaccination status, participated in acquiring the data and in designing the study, helped to develop the idea of the study and critically revised the manuscript. KK is the principal investigator of the JAGES project, helped to develop the idea of the study, participated in acquiring the data and in designing the study, and critically revised the manuscript. All authors have read and approved the final manuscript. Funding This study used data from the Japan Gerontological Evaluation Study (JAGES). This study was supported by Grant-in-Aid for Scientific Research (15H01972, 15H04781, 15H05059, 15K03417, 15K03982, 15K16181, 15K17232, 15K18174, 15K19241, 15K21266, 15KT0007, 15KT0097, 16H05556, 16K09122, 16K00913, 16K02025, 16K12964, 16K13443, 16K16295, 16K16595, 16K16633, 16K17256, 16K17281, 16K19247, 16K19267, 16K21461, 16K21465, 16KT0014, 17K04305,17K34567, 17K04306, 25253052, 25713027, 26285138, 26460828, 26780328, 18H03018, 18H04071, 18H03047, 18H00953, 18H00955, 18KK0057, 19H03901, 19H03915, 19H03860, 19K04785, 19K10641,19K11657,19K19818, 19K19455, 19K24060, 19K20909, 20H00557) from JSPS (Japan Society for the Promotion of Science); Health Labour Sciences Research Grants (H26-Choju- Ippan-006, H27-Ninchisyou-Ippan-001 H28- Choju-Ippan-002, H28-Ninchisyou- Ippan-002, H29-Chikyukibo-Ippan-001, H30-Jyunkankinado-Ippan-004, 18H04071, 19FA1012,19FA2001) from the Ministry of Health, Labour and Welfare, Japan; the Research and Development Grants for Longevity Science from Japan Agency for Medical Research and development (AMED) (JP17dk0110027, JP18dk0110027, JP18ls0110002, JP18le0110009, JP20dk0110034, JP20dk0110037), the Research Funding for Longevity Sciences from National Centre for Geriatrics and Gerontology (24-17, 24-23, 29-42, 30-30, 30-22, 20-19) ; Open Innovation Platform with Enterprises, Research Institute and Academia (OPERA, JPMJOP1831 ) from the Japan Science and Technology (JST); a grant from the Japan Foundation For Ageing And Health (J09KF00804, a grant from Innovative Research Programme on Suicide Countermeasures(1-4), a grant from Sasakawa Sports Foundation (N/A), a grant from Japan Health Promotion & Fitness Foundation (N/A), a grant from Chiba Foundation for Health Promotion & Disease Prevention (N/A), the 8020 Research Grant for fiscal 2019 from the 8020 Promotion Foundation (adopted number: 19-2- 06), a grant from Niimi University (1915010), and grants from Meiji Yasuda Life Foundation of Health and Welfare (N/A). Disclaimer The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the respective funding organisations. Competing interests None declared. Patient consent for publication  Not required. Ethics approval The ethics committee at Nihon Fukushi University approved the protocol and informed consent procedure for the present study (No. 10–05). This study conformed to the principles embodied in the Declaration of Helsinki. Provenance and peer review Not commissioned; externally peer reviewed. Data availability statement All data used are from the JAGES study and are not third-party data. All enquiries are to be addressed at the JAGES data management committee via e-mail: dataadmin.ml@jages.net. All JAGES datasets have ethical or legal restrictions for public deposition due to inclusion of sensitive information from the human participants. Following the regulation of local governments which cooperated on our survey, the JAGES data managementcommittee has imposed the restrictions upon the data. Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise. Open access This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/. ORCID iDs Kousuke Iwai-Saito http://orcid.org/0000-0002-2231-169X Yugo Shobugawa http://orcid.org/0000-0003-2851-0101