Association between calcium and vitamin D in geriatric patients hospitalized for Covid-19: Results from the GERIA-COVID study

The deficiency of 25OH vitamin D (25[OH]D) is common in the older population. It physiologically triggers secondary hyperparathyroidism resulting in normal circulating calcium levels. Adjusted calcium (CaA) is estimated by the PAYNE method and several studies report a misclassification of calcium status by corrected calcium compared to ionized calcium (CaI) in older patients. Hypocalcemia is common in older COVID-19 patients. Blunted secondary hyperparathyroidism explain this high prevalence of hypocalcemia in COVID-19. However, no studies have focused on patients older than 75 years despite the high mortality rate in this population. In the present study, the association between the different types of calcium (CaI, CaA, and total calcium [CaT]) and 25(OH)D deficiency (below 50 nmol/L) was investigated. The study of the correlation between each type of calcium was performed secondarily. Observational monocentric study focused on the GERIA-COVID database during the second wave of COVID-19 in France from October 2020 to March 2021. COVID-19 was diagnosed with RT-PCR and/or chest CT-scan. A population of 181 older COVID-19 patients (86.4 years ± 5.7) was analyzed. Sixty-three patients (34.8%) were deficient in 25(OH)D. The prevalence of total and ionized hypocalcemia was 44.1% and 39.2%, respectively. A negative association was reported in linear regression between 25(OH)D deficiency and CaA (β =-0.052 [- 0.093; -0.010], p = 0.015) as well as with CaT (β = -0.05 [-0.09; -0.01], p =0.034) in the multivariate model. No association was found between vitamin D deficiency and CaI. In the multivariate models, there was no association between each type of calcium and PTH. CaI was correlated with CaT (r = 0.39, p < 0.001) and with CaA (r = 0.15, p = 0.043). Secondary hyperparathyroidism was not activated in the context of COVID-19 in this study. After reviewing the literature, this appears to be the first study in older patients to expose such results. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial NA ### Funding Statement The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics approval was obtained from the Ethics Board of the University Hospital of Angers, France (2022-102). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All relevant data are within the manuscript and its Supporting Information files.