Figure 2

![Figure 2: Interaction analysis showing the combined effect of vitamin D deficiency and smoking on insomnia risk, suggesting a synergistic association between the two exposures.](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10759233/bin/fnut-10-1285494-g0002.jpg)

> Source: Tianci Gao et al. "The roles of serum vitamin D and tobacco smoke exposure in insomnia: a cross-sec." *Frontiers in nutrition*, 2023. PMID: [38170097](https://pubmed.ncbi.nlm.nih.gov/38170097/)

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  <img src="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10759233/bin/fnut-10-1285494-g0002.jpg" alt="Interaction analysis showing the combined effect of vitamin D deficiency and smoking on insomnia risk, suggesting a synergistic association between the two exposures." />
  <figcaption>Figure 2. Interaction analysis showing the combined effect of vitamin D deficiency and smoking on insomnia risk, suggesting a synergistic association between the two exposures.<br>  Source: Tianci Gao et al. "The roles of serum vitamin D and tobacco smoke exposure in insomnia: a cross-sec." <em>Frontiers in nutrition</em>, 2023. PMID: <a href="https://pubmed.ncbi.nlm.nih.gov/38170097/">38170097</a></figcaption>
</figure>