Olfactory Dysfunction and Sensory Abilities in Health and Disease

Olfaction, the sense of smell, plays a critical role in human physiology, influencing nutrition, safety and social communication. Dysfunction ranges from hyposmia (reduced smell) to anosmia (complete loss), and can arise through ageing, viral infection, environmental insults or neurodegenerative processes. In older adults, sensory decline often heralds broader cognitive and motor impairments, and olfactory loss may precede the onset of Alzheimer’s or Parkinson’s disease. The acute anosmia observed in viral infections such as COVID-19 has highlighted non-neuronal mechanisms of injury within the olfactory epithelium and bulb, as well as the potential for prolonged inflammation and viral persistence. At the molecular level, olfactory receptor (OR) genes and their downstream G-protein pathways define odour detection, while single-cell genomic methods have revealed remarkable cell-type diversity in the nasal mucosa. Clinically, standardised sniffing tests and brief identification assessments inform diagnosis and prognosis, with mounting evidence that olfactory impairment serves as an early biomarker for systemic and neurological disorders. Understanding sensory resilience and repair mechanisms offers routes to targeted therapies, from olfactory training to gene-based interventions, with significant implications for global public health and ageing populations.

Research from Nature Portfolio

Hierarchical deconstruction of mouse olfactory sensory neurons using tissue-level, purified and single-cell RNA sequencing has demonstrated that mature sensory neurons predominantly express a single intact OR gene at high levels, confirming the “one neuron–one receptor” principle. This work also identified a distinct non-canonical neuron subtype defined by expression of alternative signalling molecules, unveiling previously unrecognised cellular complexity in the olfactory mucosa. These insights establish a paradigm for dissecting gene expression in heterogenous tissues and provide a foundation for exploring receptor regulation, neuronal lineage and regenerative capacity in mammalian olfaction.

Olfactory Dysfunction and Sensory Abilities in Health and Disease publication trend

The graph below shows the total number of articles in olfactory dysfunction and sensory abilities in health and disease across all publications each year (not limited to Nature Index journals).

Technical terms

Anosmia: Complete loss of the sense of smell.

Hyposmia: Reduced sensitivity to odours.

Olfactory epithelium: The specialised nasal tissue housing sensory neurons and supporting cells.

Olfactory sensory neuron (OSN): A neuron projecting into the nasal cavity that detects odourant molecules via specific receptors.

Olfactory receptor (OR) gene: A gene encoding a G-protein coupled receptor responsible for binding odourants.

Monoallelic expression: The phenomenon by which only one allele of a gene is transcribed in a given cell.

Single-cell RNA-seq: A sequencing method that profiles gene expression in individual cells, revealing cellular heterogeneity.

References

1. Aging-associated sensory decline and Alzheimer’s disease. Molecular Neurodegeneration (2024).
2. Non-neuronal expression of SARS-CoV-2 entry genes in the olfactory system suggests mechanisms underlying COVID-19-associated anosmia. Science Advances (2020).
3. COVID-19–related anosmia is associated with viral persistence and inflammation in human olfactory epithelium and brain infection in hamsters. Science Translational Medicine (2021).
4. Hierarchical deconstruction of mouse olfactory sensory neurons: from whole mucosa to single-cell RNA-seq. Scientific Reports (2015).