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. 2025 Jul 9;44(1):19.
doi: 10.1186/s40101-025-00403-9.

Loneliness, insomnia symptoms, social jetlag, and vitamin D deficiency in relation to mental health problems in Japanese female university students: a cross-sectional study

Nodoka Yamashita #  1 , Shioka Ishii #  1 , Yoriko Kotoku  2 , Takuya Shuo  3 , Hiromi Eto  2 , Hideaki Kondo  4
Affiliations

Loneliness, insomnia symptoms, social jetlag, and vitamin D deficiency in relation to mental health problems in Japanese female university students: a cross-sectional study

Nodoka Yamashita et al. J Physiol Anthropol. .

Abstract

Background: Vitamin D deficiency is highly prevalent among Japanese female university students. Vitamin D deficiency is associated with physical and mental health problems, including sleep disorders. This study aimed to clarify the relationship between vitamin D deficiency and sleep and mental health problems among Japanese female university students.

Methods: Participants were 224 female university students. Blood levels of 25-hydroxyvitamin D [25(OH)D] were measured using liquid chromatography-tandem mass spectrometry for vitamin D assessment. Mental health was assessed using the K6. Sleep-wake status as a factor related to mental health was assessed using the Athens Insomnia Scale (AIS) and Munich ChronoType Questionnaire. Loneliness was assessed using the Three-Item Loneliness Scale. Factors predicting mental health problems with a K6 score ≥ 5 were explored using the Mann-Whitney U test, Fisher's exact probability test, and classification and regression tree (CART) analysis.

Results: The median (interquartile range) serum 25(OH)D concentration was 14.5 (11.8-18.3) ng/mL. Of the participants, 80.8% had vitamin D deficiency (25(OH)D < 20 ng/mL), and 26.3% had severe vitamin D deficiency (25(OH)D < 12 ng/mL). In total, 41.1% had mental health problems with a K6 score of ≥ 5. Although there was no significant association between vitamin D deficiency and sleep-wake problems, vitamin D deficiency was more prevalent among those with K6 scores ≥ 5 (P = 0.02). Compared to those with K6 < 5, those with K6 ≥ 5 had significantly higher Loneliness and AIS scores (P < 0.001), greater social jetlag (P = 0.03), shorter sleep duration on weekdays (P = 0.03), and lower serum 25(OH)D concentration (P = 0.02). In the CART analysis, the algorithm was set in the order of Loneliness score ≥ 6, AIS score ≥ 7, social jetlag ≥ 150 min, and serum 25(OH)D concentration < 14 ng/mL, and the target accuracy (95% confidence interval: CI) was 76.5 (70.3-81.9)%, and sensitivity and specificity (95% CI) were 62.2 (51.4-72.2)% and 86.3 (79.2-91.6)%, respectively.

Conclusions: Loneliness, insomnia symptoms, social jetlag, and vitamin D deficiency were associated with mental health problems among Japanese female university students.

Keywords: 25-hydroxyvitamin D; Insomnia; Loneliness; Mental health; Social jetlag; Vitamin D.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This study was approved by the Ethics Committee of Nagasaki University Graduate School of Biomedical Sciences (approval no. 21111102–4). Informed consent was obtained from all the participants. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Histogram of serum 25(OH)D level. 25(OH)D: 25-hydroxyvitamin D
Fig. 2
Fig. 2
Classification and regression trees for predicting factors associated with K6 ≥ 5. AIS, Athens insomnia scale; 25(OH)D, 25-hydroxyvitamin D; SJL, social jetlag
See this image and copyright information in PMC

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Supplementary concepts