APOE and diabetes mellitus: Furthermore, in terms of comorbidity our study ignored potential comorbidities typical in a routine care dataset, especially in a population with an average age of 70 years, including metabolic (e.g., diabetes, vitamin B12), toxic (e.g., smoking, medication), genetic (e.g., Apolipo-Proteine-E (APOE) ε4), and other states (e.g., trauma, respiratory tract infection, COVID, otolaryngological and psychiatric disorders), or vascular health with impact on olfactory functions.