{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,19]],"date-time":"2026-08-19T18:15:46Z","timestamp":1787163346010,"version":"build-2736575974"},"reference-count":26,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2021,2,9]],"date-time":"2021-02-09T00:00:00Z","timestamp":1612828800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100007771","name":"\u015al\u0105ski Uniwersytet Medyczny","doi-asserted-by":"publisher","award":["KNW-1-079\/K\/9\/Z"],"award-info":[{"award-number":["KNW-1-079\/K\/9\/Z"]}],"id":[{"id":"10.13039\/100007771","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJERPH"],"abstract":"<jats:p>Background. Generally, most vitamin D in the human body (90\u201395%) is produced in the skin during exposure to sunlight. The effectiveness of this process depends on several biological and physical factors, e.g., age or latitude. Skin synthesis of vitamin D among elderly people is reduced. The aim of the study was to assess serum 25-hydroxyvitamin D [25(OH)D] seasonal variations in elderly patients hospitalized at the geriatric department. Methods. The study was carried out on 242 patients aged 60 years or older hospitalized at the geriatric department. The study group was categorized by four seasons as well as month. Results. The median (interquartile range) 25(OH)D concentration among all patients (n = 242) was 33.95 (26.96\u201345.18) nmol\/L. There was no statistical significance in the median serum 25(OH)D concentration with regard to each of the four seasons: in the spring 32.95 (25.96\u201343.68) nmol\/L, in the summer 38.69 (27.46\u201350.67) nmol\/L, in the autumn 33.45 (27.08\u201344.18) nmol\/L, in the winter 34.57 (23.46\u201343.93) nmol\/L, (p = 0.48). Conclusions. Vitamin D deficiency was observed in all geriatric patients, irrespective of the season. The results of the study indicate no significant differences in median vitamin D concentration among the hospitalized patients across all four seasons. Even in the summer months, in our climate, it is fairly difficult for an elderly person to produce an adequate amount of vitamin D through the skin. Therefore, proper vitamin D supplementation is recommended and should be implemented in the elderly irrespective of the season.<\/jats:p>","DOI":"10.3390\/ijerph18041676","type":"journal-article","created":{"date-parts":[[2021,2,9]],"date-time":"2021-02-09T23:43:16Z","timestamp":1612914196000},"page":"1676","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Lack of Seasonal Variations in Vitamin D Concentrations among Hospitalized Elderly Patients"],"prefix":"10.3390","volume":"18","author":[{"given":"Justyna","family":"Nowak","sequence":"first","affiliation":[{"name":"Department of Cardiovascular Disease Prevention, Department of Metabolic Disease Prevention, Faculty of Health Sciences in Bytom, Medical University of Silesia, 41-900 Bytom, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bartosz","family":"Hudzik","sequence":"additional","affiliation":[{"name":"Department of Cardiovascular Disease Prevention, Department of Metabolic Disease Prevention, Faculty of Health Sciences in Bytom, Medical University of Silesia, 41-900 Bytom, Poland"},{"name":"Third Department of Cardiology, Silesian Center for Heart Disease, Faculty of Medical Sciences in Zabrze, Medical University of Silesia, 41-800 Zabrze, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7583-8965","authenticated-orcid":false,"given":"Pawe\u0142","family":"Jagielski","sequence":"additional","affiliation":[{"name":"Department of Nutrition and Drug Research, Faculty of Health Science, Jagiellonian University Medical College, 31-007 Cracow, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karolina","family":"Kulik-Kupka","sequence":"additional","affiliation":[{"name":"Department of Nutrition-Related Disease Prevention, Department of Metabolic Disease Prevention, Faculty of Health Sciences in Bytom, Medical University of Silesia, 41-900 Bytom, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Aleksander","family":"Danikiewicz","sequence":"additional","affiliation":[{"name":"Department of Nutrition-Related Disease Prevention, Department of Metabolic Disease Prevention, Faculty of Health Sciences in Bytom, Medical University of Silesia, 41-900 Bytom, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8670-8581","authenticated-orcid":false,"given":"Barbara","family":"Zubelewicz-Szkodzi\u0144ska","sequence":"additional","affiliation":[{"name":"Department of Nutrition-Related Disease Prevention, Department of Metabolic Disease Prevention, Faculty of Health Sciences in Bytom, Medical University of Silesia, 41-900 Bytom, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,2,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Umar, M.U., Sastry, K.S., and Chouchane, A.I. 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