Poor sleep quality, vitamin D deficiency and depression in the stroke population: A cohort study

•The proportion of poor sleep quality and vitamin D deficiency was higher in patients with PSD than those without PSD.•HAMD score was positively correlated with the PSQI score, and negatively correlated with serum vitamin D levels.•Prestroke poor sleep quality was associated with a higher risk of PSD in the vitamin D deficiency group.•The relationship between vitamin D deficiency and PSD was mediated by poststroke sleep quality.