This prospective longitudinal cohort study will enroll adults aged 50 years and older to characterize olfactory dysfunction in aging. Participants will undergo comprehensive olfactory testing, cognitive assessment, biomarker collection, and imaging to identify clinically relevant phenotypes based on anatomic site of dysfunction. The study will also evaluate the impact of olfactory dysfunction on quality of life and identify baseline factors associated with changes in olfactory function over time.

Olfactory dysfunction is common in older adults and is associated with impaired quality of life and increased mortality, yet underlying mechanisms and clinically relevant classifications remain poorly defined. Prior studies have relied on limited screening methods and have not adequately characterized the anatomic sites or mechanisms contributing to olfactory loss.

This prospective longitudinal cohort study will enroll adults aged 50 years and older to comprehensively evaluate olfactory function and its determinants. Participants will undergo psychophysical olfactory testing using Sniffin' Sticks (threshold, discrimination, and identification), cognitive assessment, nasal endoscopy, and olfactory mucus collection for biomarker analysis. A subset of participants will also undergo magnetic resonance imaging to assess peripheral and central olfactory structures.

The primary objective is to establish clinically relevant phenotypes of olfactory dysfunction based on olfactory testing and cognitive function, corresponding to peripheral, sensorineural, or central mechanisms. Secondary objectives are to determine the impact of olfactory dysfunction on quality of life, depression, social isolation, and nutrition using validated patient-reported outcome measures, and to identify baseline factors that predict longitudinal changes in olfactory function.

Participants will be followed annually with repeat olfactory testing and outcome assessments to evaluate changes over time and identify predictors of olfactory decline. This study aims to improve understanding of olfactory dysfunction in aging and provide a foundation for future diagnostic and therapeutic strategies.

Inclusion Criteria:

• Age: 50 years or older
• Ability to follow instructions and understand consent process in English
• Adequate visual, auditory, or motor functioning to complete items in the test battery or availability of assistance or assist devices to complete tasks

Exclusion Criteria:

- Vulnerable populations including prisoners or institutionalized individuals

Community-dwelling adults aged 50 years and older recruited from the Medical University of South Carolina (MUSC) and surrounding community, including clinic patients and individuals responding to advertisements, who may have normal olfactory function or varying degrees of olfactory dysfunction.

Protection of individual privacy