{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,13]],"date-time":"2026-01-13T12:16:00Z","timestamp":1768306560293,"version":"3.49.0"},"reference-count":31,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,1,13]],"date-time":"2026-01-13T00:00:00Z","timestamp":1768262400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Public Health"],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Clinical evidence on how social network diversity (SND) influences the risk of infection and disease severity during the coronavirus disease 2019 (COVID-19) pandemic remains limited. We aim to investigate the associations between SND and the risk of COVID-19 infection and disease severity using a large-scale longitudinal cohort study.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We analyzed data from participants in a longitudinal study, the Japan COVID-19 and Society Internet Survey (JACSIS) between 2020 and 2023. The SND score was calculated as the sum of seven distinct types of social networks. COVID-19 infection was assessed as ever infection, and severity was defined as oxygen-requiring admission, using a self-reported questionnaire. Poisson regression with robust standard errors estimated risk ratios (RRs) and 95% confidence intervals (CIs), adjusting for sociodemographic and clinical characteristics.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Of 13,713 participants (mean age 53.2\u202f\u00b1\u202f15.7\u202fyears, 46.4% women), 3,251 (23.7%) developed COVID-19, and among infected individuals, 277 (8.5%) required oxygen therapy. Higher SND scores were associated with COVID-19 infection with linear trend (SND score 7 vs. 0: adjusted RR 2.49; 95% CI 2.11\u20132.95). In contrast, the association between SND score and disease severity followed a U-shaped pattern, with 4\u20135 SND showing the lowest risk of oxygen-requiring admission (adjusted RR 0.15; 95% CI 0.11\u20130.30) compared to those with 0 SND.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>While higher SND was associated with increased COVID-19 infection risk, moderate social network diversity appeared protective against severe disease outcomes. These findings suggest a complex trade-off between exposure risk and potential health benefits of social networks during infectious disease outbreaks.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fpubh.2025.1730268","type":"journal-article","created":{"date-parts":[[2026,1,13]],"date-time":"2026-01-13T05:14:05Z","timestamp":1768281245000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Social network diversity and COVID-19 infection and severity risk: a longitudinal population study"],"prefix":"10.3389","volume":"13","author":[{"given":"Takahiro","family":"Suzuki","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takeo","family":"Fujiwara","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takahiro","family":"Tabuchi","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2026,1,13]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"385","DOI":"10.1056\/NEJMp2213920","article-title":"Facing the new covid-19 reality","volume":"388","author":"El-Sadr","year":"2023","journal-title":"N Engl J Med"},{"key":"ref2","doi-asserted-by":"publisher","first-page":"90","DOI":"10.1007\/s12016-022-08921-5","article-title":"Risk and protective factors for COVID-19 morbidity, severity, and mortality","volume":"64","author":"Zhang","year":"2023","journal-title":"Clin Rev Allergy Immunol"},{"key":"ref3","doi-asserted-by":"publisher","first-page":"384","DOI":"10.1186\/s12916-023-03055-7","article-title":"Social connection and mortality in UK biobank: a prospective cohort analysis","volume":"21","author":"Foster","year":"2023","journal-title":"BMC Med"},{"key":"ref4","doi-asserted-by":"publisher","first-page":"e2451580","DOI":"10.1001\/jamanetworkopen.2024.51580","article-title":"Patterns of social connection among older adults in England","volume":"7","author":"Bu","year":"2024","journal-title":"JAMA Netw Open"},{"key":"ref5","doi-asserted-by":"publisher","first-page":"1940","DOI":"10.1001\/jama.1997.03540480040036","article-title":"Social ties and susceptibility to the common cold","volume":"277","author":"Cohen","year":"1997","journal-title":"JAMA"},{"key":"ref6","doi-asserted-by":"publisher","first-page":"294","DOI":"10.1037\/0278-6133.21.3.294","article-title":"Being popular can be healthy or unhealthy: stress, social network diversity, and incidence of upper respiratory infection","volume":"21","author":"Hamrick","year":"2002","journal-title":"Health Psychol"},{"key":"ref7","doi-asserted-by":"publisher","first-page":"400","DOI":"10.1111\/rssa.12753","article-title":"On the interplay of regional mobility, social connectedness and the spread of COVID-19 in Germany","volume":"185","author":"Fritz","year":"2022","journal-title":"J R Stat Soc Ser A Stat Soc"},{"key":"ref8","article-title":"Office of the U.S. Surgeon General. Our Epidemic of Loneliness and Isolation: The U.S. Surgeon General\u2019s Advisory on the Healing Effects of Social Connection and Community. Washington, DC: U.S. Department of Health and Human Services;","year":""},{"key":"ref9","doi-asserted-by":"publisher","first-page":"84","DOI":"10.1016\/j.ijid.2023.04.399","article-title":"Characteristics and clinical effectiveness of COVID-19 vaccination in hospitalized patients in omicron-dominated epidemic wave - a nationwide study in Japan","volume":"132","author":"Tanaka","year":"2023","journal-title":"Int J Infect Dis"},{"key":"ref10","doi-asserted-by":"publisher","first-page":"101194","DOI":"10.1016\/j.jjie.2022.101194","article-title":"How does the impact of the COVID-19 state of emergency change? An analysis of preventive behaviors and mental health using panel data in Japan","volume":"64","author":"Yamamura","year":"2022","journal-title":"J Jpn Int Econ"},{"key":"ref11","volume-title":"Statista. Japan: COVID-19 vaccination rate 2023","year":""},{"key":"ref12","volume-title":"Nippon Institute for Research Advancement (NIRA). Characteristics and issues of Japan\u2019s response to COVID-19 - an international comparison. NIRA Opinion Paper No. 57. Tokyo: NIRA; 2021","year":""},{"key":"ref13","doi-asserted-by":"publisher","first-page":"135","DOI":"10.1186\/s13052-023-01485-w","article-title":"Severity of SARS-CoV-2 infection in a hospital population: a clinical comparison across age groups","volume":"49","author":"Rosazza","year":"2023","journal-title":"Ital J Pediatr"},{"key":"ref14","doi-asserted-by":"publisher","first-page":"e139","DOI":"10.3346\/jkms.2021.36.e139","article-title":"Clinical characteristics of COVID-19: risk factors for early oxygen requirement after hospitalization","volume":"36","author":"Suh","year":"2021","journal-title":"J Korean Med Sci"},{"key":"ref15","doi-asserted-by":"publisher","first-page":"e0249984","DOI":"10.1371\/journal.pone.0249984","article-title":"Oxygen provision to severely ill COVID-19 patients at the peak of the 2020 pandemic in a Swedish district hospital","volume":"17","author":"Hvarfner","year":"2022","journal-title":"PLoS One"},{"key":"ref16","doi-asserted-by":"publisher","first-page":"121594","DOI":"10.1016\/j.envpol.2023.121594","article-title":"Long-term exposure to air pollution and COVID-19 severity: a cohort study in greater Manchester, United Kingdom","volume":"327","author":"Hyman","year":"2023","journal-title":"Environ Pollut"},{"key":"ref17","doi-asserted-by":"publisher","first-page":"e001038","DOI":"10.1136\/bmjresp-2021-001038","article-title":"Effect modification by age of the association between obstructive lung diseases, smoking, and COVID-19 severity","volume":"8","author":"Moschovis","year":"2021","journal-title":"BMJ Open Respir Res"},{"key":"ref18","doi-asserted-by":"publisher","first-page":"e2134147","DOI":"10.1001\/jamanetworkopen.2021.34147","article-title":"Disparities in COVID-19 outcomes by race, ethnicity, and socioeconomic status: a systematic-review and meta-analysis: a systematic review and meta-analysis","volume":"4","author":"Magesh","year":"2021","journal-title":"JAMA Netw Open"},{"key":"ref19","doi-asserted-by":"publisher","first-page":"2233","DOI":"10.2105\/AJPH.2012.300795","article-title":"Social connectedness and disease transmission: social organization, cohesion, village context, and infection risk in rural Ecuador","volume":"102","author":"Zelner","year":"2012","journal-title":"Am J Public Health"},{"key":"ref20","doi-asserted-by":"publisher","first-page":"121","DOI":"10.1001\/archpedi.156.2.121","article-title":"Influence of attendance at day care on the common cold from birth through 13 years of age","volume":"156","author":"Ball","year":"2002","journal-title":"Arch Pediatr Adolesc Med"},{"key":"ref21","doi-asserted-by":"publisher","first-page":"782","DOI":"10.1001\/jama.2020.12839","article-title":"Pathophysiology, transmission, diagnosis, and treatment of coronavirus disease 2019 (COVID-19): a review: a review","volume":"324","author":"Wiersinga","year":"2020","journal-title":"JAMA"},{"key":"ref22","doi-asserted-by":"publisher","first-page":"e488","DOI":"10.1016\/S2214-109X(20)30074-7","article-title":"Feasibility of controlling COVID-19 outbreaks by isolation of cases and contacts","volume":"8","author":"Hellewell","year":"2020","journal-title":"Lancet Glob Health"},{"key":"ref23","doi-asserted-by":"publisher","first-page":"540","DOI":"10.1126\/science.3399889","article-title":"Social relationships and health","volume":"241","author":"House","year":"1988","journal-title":"Science"},{"key":"ref24","doi-asserted-by":"publisher","first-page":"209","DOI":"10.1111\/ggi.14118","article-title":"Cross-national comparison of social isolation and mortality among older adults: a 10-year follow-up study in Japan and England","volume":"21","author":"Saito","year":"2021","journal-title":"Geriatr Gerontol Int"},{"key":"ref25","doi-asserted-by":"publisher","first-page":"990","DOI":"10.1136\/jech-2017-210236","article-title":"Effects of social network diversity on mortality, cognition and physical function in the elderly: a longitudinal analysis of the Chicago health and aging project (CHAP)","volume":"72","author":"Ali","year":"2018","journal-title":"J Epidemiol Community Health"},{"key":"ref26","doi-asserted-by":"publisher","first-page":"711","DOI":"10.1097\/PSY.0000000000000685","article-title":"Two distinct immune pathways linking social relationships with health: inflammatory and antiviral processes: inflammatory and antiviral processes","volume":"81","author":"Leschak","year":"2019","journal-title":"Psychosom Med"},{"key":"ref27","doi-asserted-by":"publisher","first-page":"279","DOI":"10.1016\/j.bbi.2007.10.011","article-title":"Social networks and immunosuppression during stress: relationship conflict or energy conservation?","volume":"22","author":"Segerstrom","year":"2008","journal-title":"Brain Behav Immun"},{"key":"ref28","doi-asserted-by":"publisher","first-page":"1956","DOI":"10.1038\/s41467-022-29522-y","article-title":"Using high-resolution contact networks to evaluate SARS-CoV-2 transmission and control in large-scale multi-day events","volume":"13","author":"Pung","year":"2022","journal-title":"Nat Commun"},{"key":"ref29","doi-asserted-by":"publisher","first-page":"3442","DOI":"10.1038\/s41380-020-00861-w","article-title":"A paradox of social distancing for SARS-CoV-2: loneliness and heightened immunological risk","volume":"25","author":"Rozenkrantz","year":"2020","journal-title":"Mol Psychiatry"},{"key":"ref30","doi-asserted-by":"publisher","first-page":"20552076231204744","DOI":"10.1177\/20552076231204746","article-title":"Leveraging digital technology for social connectedness among adults with chronic conditions: a systematic review","volume":"9","author":"Wright","year":"2023","journal-title":"Digit Health"},{"key":"ref31","doi-asserted-by":"publisher","first-page":"25230","DOI":"10.1038\/s41598-025-09861-8","article-title":"The relationships between social internet use, social contact, and loneliness in older adults","volume":"15","author":"Janssen","year":"2025","journal-title":"Sci Rep"}],"container-title":["Frontiers in Public 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