Decreased levels of vitamin D in Post-Corona Virus-19 Disease syndrome (PCS) patients compared to a control group.

Background & aims: Vitamin D deficiency is defined by most experts as a level of less than 20 ng/ml. Studies have shown a relationship between musculoskeletal pain, muscle weakness, headache, and fatigue with low vitamin D level. The term Post-Corona Virus-19 Disease syndrome (PCS) describes new, returning or ongoing symptoms more than 12 weeks after Corona Virus Disease -19 (COVID-19) infection which cannot be explained by any other disorders or illnesses. The most prominent symptoms in PCS are fatigue, headache, and attention disorders. These similarities in PCS and vitamin D deficiency leads to the hypothesis of an association. The aim of this study was to find possible differences in vitamin D levels between PCS patients and a control group without PCS.

Methods: We measured vitamin D levels from April 2021 to December 2022 in 75 (2021) and 73 (2022) subjects (PCS) and compared these values with data from 2019 to 2022 in a non-PCS control group (non-PCS).

Results: We found significantly lower (p < 0,05) vitamin D levels in the PCS cohort (2021: 17,04 ± 8,0 ng/ml; 2022: 17,6 ± 6,6 ng/ml) compared to all years of the non-PCS group (2019: 23,7 ± 14,7 ng/ml; 2020:22,3 ± 13,7 ng/ml; 2021: 22,4 ± 12,3 ng/ml; 2022: 22,6 ± 11,0 ng/ml). There were no significant differences in vitamin D levels within the different years of the non-PCS group and when comparing the two PCS groups.

Conclusion: The results of the study recorded for the first-time decreased vitamin D values in a PCS cohort compared to a control group. This raises the question of whether vitamin D deficiency influences PCS symptoms or whether they are merely the consequences of the limitations of PCS.