维生素C是人体生物学中发挥重要作用的必需微量营养素。维生素C缺乏症被定义为血浆抗坏血酸水平低于23μmol/L，并与心血管疾病、癌症或神经认知障碍等许多不良结果相关。许多危险因素在老年人中普遍存在，使他们特别容易患上维生素C缺乏症。这些危险因素包括维生素摄入减少、与多病理相关的更高维生素代谢以及多药物治疗所导致的医源性。然而，老年人群中维生素C缺乏症的具体患病率和危险因素的资料不全。更好地了解维生素C缺乏症的患病率和危险因素可能有助于改善老年人的维生素C状况并预防其后果。为了回答这些问题，我们设计了一项在法国里昂的老年住院患者群体中的单中心横断面研究。需要样本量为385例患者，以估计维生素C缺乏症的患病率。该研究向所有年龄超过75岁的符合条件的患者提供。对参与患者进行了系统地评估了血浆维生素C状况，并收集了医学和老年评估的变量。对于维生素C严重缺乏的患者，安排了口服补充和后续电话随访，以确保治疗完成和耐受性。该方案已获得独立的国家伦理委员会批准，并符合方法学要求。最终结果将在同行评审的期刊上发表，并通过会议传播。NCT05668663.© 作者（或他们的雇主）2023。在CC BY-NC许可下允许重新使用，不允许商业再利用。由BMJ出版。

Vitamin C is an essential micronutrient playing crucial roles in human biology. Hypovitaminosis C is defined by a plasmatic ascorbemia below 23 µmol/L and is associated with numerous outcomes such as cardiovascular diseases, cancers or neurocognitive disorders. Numerous risk factors are common among older adults making them particularly susceptible to hypovitaminosis C. These risk factors include reduced vitamin intakes, higher vitamin metabolism related to polypathology, and iatrogeny because of polypharmacy. However, the precise prevalence of hypovitaminosis C and its risk factors are poorly documented within the geriatric population.A better knowledge of hypovitaminosis C prevalence and risk factor may lead to improving the vitamin C status among older people and prevent its consequences.To answer these questions, we designed a monocentric cross-sectional study in a population of older hospitalised patients in Lyon, France. A sample size of 385 patients was needed to estimate hypovitaminosis C prevalence. The study was proposed to all eligible patient aged more than 75 years old entering the participating acute geriatric unit. The plasmatic vitamin C status was systematically assessed for participating patients, and variables part of the medical and geriatric evaluation were collected. For patients with severe vitamin C depletion, an oral supplementation and a follow-up phone call were organised to ensure treatment completion and tolerance.The protocol has been approved by an independent national ethics committee and meets the methodological requirements. Final outcomes will be published in a peer-reviewed journal and disseminated through conferences.NCT05668663.© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.