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. 2025 Aug 12;25(1):2745.
doi: 10.1186/s12889-025-23778-x.

What factors are associated with new social isolation years after the great East Japan Earthquake?: findings from the TMM CommCohort study

Yuka Kotozaki  1   2 , Kozo Tanno  3   4 , Kotaro Otsuka  3   5 , Ryohei Sasaki  6 , Makoto Sasaki  3   7
Affiliations

What factors are associated with new social isolation years after the great East Japan Earthquake?: findings from the TMM CommCohort study

Yuka Kotozaki et al. BMC Public Health. .

Abstract

Background: The effects of disaster experiences on social isolation and related factors remain unclear. Using longitudinal data, this study aimed to identify new social isolation and its associated factors after the Great East Japan Earthquake (GEJE), which occurred on March 11, 2011.

Methods: We analyzed longitudinal data from 12,795 participants who responded to self-report questionnaires, utilizing the Lubben Social Network Scale-6 (LSNS-6). Participants included 4,450 men and 8,345 women; the sex ratio of the analytic sample was broadly consistent with that of the study population at baseline. Baseline data were collected between fiscal years (FY) 2013 and 2015, and follow-up data were collected between FY2017 and FY2019. Social isolation was defined as a score < 12 on the LSNS-6. Based on their level of social isolation in the second survey, participants were categorized into two groups: not socially isolated and newly socially isolated. To examine factors associated with new social isolation, we used logistic regression analysis to calculate multivariate-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for the newly socially isolated group versus the not socially isolated group by sex.

Results: New social isolation was associated with several lifestyle and psychosocial factors, exhibiting differences between men and women. Among men, factors associated with new social isolation were not currently smoking among those without house damage, living alone among those with house damage, and no exercise habits among those who experienced the death of family members due to GEJE. Among women who lost family members due to GEJE, insomnia was associated with new social isolation.

Conclusion: The occurrence of new social isolation years after the GEJE and its associated factors varied by sex and the presence of GEJE-related damages. To prevent new social isolation in the aftermath of a large-scale natural disaster, it is crucial to consider sex-specific factors contributing to social isolation.

Keywords: Community-based cohort study; Damage situation; Related factors; Social isolation.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: In accordance with the Declaration of Helsinki (1991), written informed consent was obtained from all participants. The Ethics Committee of Iwate Medical University (first approval: HG H25-2; most recent approval: HG 2018-004) approved all the study procedures. The study was carried out in accordance with the Declaration of Helsinki (1991). Consent for publication: Not required. Competing interests: The authors declare no competing interests.

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