Shift work and excess daytime sleepiness, depression (nurses in Turkey)

Association of Shift Work and Serum Vitamin D Levels with Excessive Daytime Sleepiness, Anxiety Symptoms, and Depressive Symptoms in Female Nurses

Metabolites (MDPI), Oct 16, 2026, https://doi.org/10.3390/metabo16100786

İbrahim Safa Karcı, Kamile Marakoğlu, Fatma Hümeyra Yerlikaya, Zeynep Ebru Şener

Summary by Claude Opus 5.5 - October 2026

Bottom line: Female nurses at a Turkish university hospital had very low vitamin D, averaging 13 ng/mL even though blood was drawn May–July, the sunniest months. Vitamin D levels were not linked to daytime sleepiness, anxiety, or depression symptoms. However, only about 2% of the nurses reached 30 ng/mL, so the study could not test what adequate vitamin D might do.

Study: Cross-sectional (a one-time snapshot) of 312 female nurses in Konya, Türkiye; peer-reviewed. No vitamin D was given, and anyone who had taken vitamin D in the previous 3 months was excluded. 25(OH)D was measured with the Roche Elecsys assay, which is standardized to LC-MS/MS.

Findings:

84% were deficient (<20 ng/mL), 13.5% were insufficient (20–30 ng/mL), and only ~2% (about 7 nurses) were ≥30 ng/mL
Night shift vs day shift: 89% vs 80% deficient; mean 12.2 vs 13.9 ng/mL
Night-shift nurses had 2× the odds of deficiency, but this disappeared after adjustment. Night-shift nurses were ~4 years younger, and each extra year of age lowered the odds of deficiency by ~8.5%
Nurses who had taken vitamin D at some earlier time were less often deficient (borderline, p = 0.05; not significant after adjustment)
Body-covering vs seasonal clothing made no difference
25(OH)D had essentially zero correlation with sleepiness, anxiety, or depression scores (r = −0.007 to 0.035)
Daytime sleepiness (31% of nurses) was linked to anxiety (2.8× adjusted odds) and to depressive symptoms (1.9×)

The authors caution that their null result "should be interpreted not as evidence that there is no relationship."

What this does NOT show

That vitamin D is irrelevant to sleep or mood: almost no one had enough vitamin D to compare against
What supplementation would do: no vitamin D was given
Cause or direction: it is a single snapshot
Results for other settings: one hospital, one season, and sun exposure, diet, and sleep duration were not measured
Fully reliable estimates: 92 of 404 eligible nurses dropped out, and many comparisons were made with no correction for multiple testing

ShiftworknursesvitaminD.pdf

Abstract

Background/Objectives: This study evaluated the associations of shift work with serum vitamin D levels, excessive daytime sleepiness (EDS), and symptoms of anxiety and depression among female nurses working at a university hospital.

Methods: This was an analytical cross-sectional study. Sociodemographic and occupational characteristics were collected via a structured questionnaire. EDS was assessed using the Epworth Sleepiness Scale (ESS), and symptoms of anxiety and depression were assessed using the Hospital Anxiety and Depression Scale (HADS). Serum 25-hydroxyvitamin D [25(OH)D] levels were measured by electrochemiluminescence (Elecsys Vitamin D total II, cobas e 801). Deficiency was defined as <20 ng/mL.

Results: Mean age was 32.4 ± 6.8 years; 44.9% worked night shifts. Mean 25(OH)D level was 13.16 ± 7.87 ng/mL, with deficiency in 84.3% and insufficiency in 13.5%. EDS was present in 30.8%, anxiety symptoms in 26.9%, and depressive symptoms in 46.2%. Vitamin D levels were lower in night-shift nurses, though not significantly (p = 0.056).

In univariable logistic regression analysis, night-shift work was associated with vitamin D deficiency (OR = 2.053; 95% CI: 1.068-3.948; p = 0.031), but this association was not significant after adjustment (aOR = 1.136; 95% CI: 0.541-2.389; p = 0.736).

EDS (excessive daytime sleepiness ) was associated with anxiety symptoms (aOR = 2.795; 95% CI: 1.553-5.031; p = 0.001)

and depressive symptoms (aOR = 1.887; 95% CI: 1.077-3.306; p = 0.027).

Anxiety and depressive symptoms were associated with each other (aOR = 7.332 and 7.285; p < 0.001).

Conclusions: A high prevalence of vitamin D deficiency, EDS, anxiety symptoms and depressive symptoms was observed among female nurses. Vitamin D status was not significantly associated with EDS, anxiety symptoms, or depressive symptoms, whereas EDS was associated with both anxiety and depressive symptoms.

Shift work and excess daytime sleepiness, depression (nurses in Turkey)

Association of Shift Work and Serum Vitamin D Levels with Excessive Daytime Sleepiness, Anxiety Symptoms, and Depressive Symptoms in Female Nurses

Abstract

Related in VitaminDWiki