Social determinants of health associated with underweight among middle-aged Japanese men and women: a cross-sectional study†

Akiko Morimoto; Hideaki Furuki; Aina Muta; Liqian Sun; Nao Sonoda

doi:10.2478/fon-2026-0035

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Social determinants of health associated with underweight among middle-aged Japanese men and women: a cross-sectional study†

Frontiers of Nursing

Volume 13 (2026): Issue 3 (September 2026)

By: Akiko Morimoto, Hideaki Furuki, Aina Muta, Liqian Sun and Nao Sonoda

Open Access

|Sep 2026

Abstract

Objective

This study examined the gender-specific associations between social determinants of health and underweight status among middle-aged Japanese adults.

Methods

This cross-sectional study analyzed data from a postal survey of 2799 healthy middle-aged Japanese adults. Underweight was defined as a body mass index (BMI) <18.5 kg/m² based on self-reported height and weight. The following variables were included as covariates in the multivariable-adjusted models: age, economic status, educational level, health literacy, living alone status, daily working hours, smoking status, drinking status, physical activity, sleep quality, and self-reported mental health.

Results

Of the 2799 participants, the prevalence of underweight was 5.0% in men (59/1170) and 14.9% in women (242/1629). Among men, living alone was significantly associated with underweight (adjusted risk ratio [RR]: 1.97, 95% confidence interval [CI]: 1.16–3.36), as was current smoking (RR: 1.75, 95% CI: 1.04–2.95). Self-reported average and poor/very poor mental health also had strong associations with underweight among men: average mental health (RR: 2.51, 95% CI: 1.21–5.19) and poor/very poor mental health (RR: 3.05, 95% CI: 1.36–6.87) versus very good/good mental health. Among women, no significant associations were observed. However, sensitivity analyses indicated an association between smoking and being underweight.

Conclusions

This study identified gender-specific factors associated with underweight in healthy middle-aged Japanese adults, highlighting the importance of social and psychological influences on nutritional status. Gender-specific approaches may be essential for early identification of underweight and appropriate interventions.

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Articles in this issue

DOI: https://doi.org/10.2478/fon-2026-0035 | Journal eISSN: 2544-8994 | Journal ISSN: 2097-5368

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Language: English

Page range: 309 - 316

Submitted on: Oct 28, 2025

Accepted on: Nov 6, 2025

Published on: Sep 25, 2026

Published by: Shanxi Medical Periodical Press

In partnership with: Paradigm Publishing Services

Keywords:

Japan,

mental health,

middle-aged adults,

social determinants of health,

underweight

Related subjects:

Medicine,

Assistive professions, nursing

© 2026 Akiko Morimoto, Hideaki Furuki, Aina Muta, Liqian Sun, Nao Sonoda, published by Shanxi Medical Periodical Press
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 13 (2026): Issue 3 (September 2026)