Intranasal insulin for the treatment of olfactory dysfunction: a protocol for a systematic review and meta-analysis.

Introduction: Olfactory dysfunction (OD) is a prevalent nasal affliction that has detrimental effects on the patients' quality of life and safety. Conventional therapeutic strategies have various limitations such as high costs, prolonged treatment durations and adverse side effects. Intranasal insulin is a novel intervention for the management of OD. To date, few systematic reviews have been conducted to evaluate the efficacy of this intervention. This study aims to critically assess the therapeutic efficacy and safety profile of intranasal insulin administration in patients with OD.

Methods and analysis: A systematic literature search will be performed on several databases, including PubMed, the Cochrane Central Register of Controlled Trials, Embase, SinoMed and China National Knowledge Infrastructure (CNKI), to identify studies investigating the efficacy of intranasal insulin in treating OD. The search will span from database inception to 1 April 2024, including publication in Chinese and English languages. Data will be retrieved from the literature by two independent investigators. Subsequently, the data will be processed using RevMan V.5.3.5. The meta-analysis will be performed in line with the Cochrane Handbook guidelines. The clinical efficacy and safety of intranasal insulin for OD will be appraised based on various outcomes, including overall symptom improvement, the Connecticut Chemosensory Clinical Research Center score, variations in serum glucose levels, body mass index variations and the incidence of adverse events.

Ethics and dissemination: This will be a systematic review of available literature; thus, no ethical clearance is required. The results of this study will be shared through journal publication or presented at an academic conference.

Trial registration number: According to the guidelines, our systematic review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) on 16 May 2024 (registration number CRD42024543438).