Taste, Smell, and Functional Ageing

Key Takeaways

Taste and smell are healthspan-relevant senses because they shape flavor perception, appetite, food choice, hazard detection, social participation, and quality of life. [1] [2]
Age-related smell change can reflect peripheral olfactory epithelium exposure, nasal disease, cumulative environmental injury, central nervous system change, medication effects, and neurodegenerative pathology. [1] [2]
Taste decline is heterogeneous and can involve taste buds, saliva, oral health, medications, systemic disease, smell loss, and central processing rather than a single taste-specific ageing pathway. [4] [5] [6]
Associations with frailty, malnutrition, mobility, cognition, and mortality are substantial in observational research, but causal direction and pathway size remain difficult to separate from shared ageing biology. [7] [8] [9] [10]

Taste and smell are often treated as quality-of-life senses, but they also sit at the boundary between sensory biology and everyday function. Smell supports flavor perception, environmental warning signals, social cues, and memory-linked behavior, while taste helps evaluate nonvolatile food chemicals and interacts with saliva, oral health, chewing, appetite, and nutrition. [1] [2] [4]

Who This Is Useful For

This page is useful for readers trying to understand why chemosensory ageing appears in studies of frailty, malnutrition, cognition, mobility, mortality, and multisensory decline. It is especially relevant when interpreting evidence that connects smell or taste tests with broad healthspan outcomes rather than with nose, mouth, or food enjoyment alone. [3] [7] [8] [9]

What Changes With Ageing Smell

Olfactory ageing can involve several biological levels. Reviews describe changes in nasal airflow, olfactory epithelium integrity, receptor neuron turnover, cumulative viral or environmental injury, medication and disease exposures, olfactory bulb and cortical processing, and neurodegenerative protein pathology. [1] [2]

These mechanisms make smell loss difficult to interpret as one simple marker. Poor odor identification can reflect peripheral sensory loss, semantic or memory demands, central nervous system change, general health burden, or combinations of these pathways. This is why olfactory testing can be informative in ageing research while still being nonspecific at the individual-mechanism level. [1] [2] [11]

What Changes With Ageing Taste

Taste ageing is also heterogeneous. Systematic and narrative reviews describe higher detection or recognition thresholds in older adults for some taste qualities, but the pattern differs by taste quality, measurement method, oral health, saliva, medication exposure, systemic disease, nutritional status, and smell function. [4] [5] [6]

Many perceived taste complaints are partly flavor complaints because flavor depends heavily on retronasal olfaction during eating. Reduced saliva, dry mouth, dentures, oral inflammation, chewing difficulty, polypharmacy, and smell impairment can therefore change food experience even when basic gustatory receptor function is not the only altered system. [4] [5] [6]

Pathways From Chemosensation to Function

Pathway	Functional Link	Healthspan Relevance
Food and nutrition	Smell and taste influence flavor, appetite, food preference, salivation, and the sensory reward of eating. [1] [4]	Links chemosensory loss with malnutrition risk, unintentional weight loss, and reduced dietary variety in some older-adult studies. [4] [6]
Frailty and reserve	Olfactory impairment can cluster with lower physiologic reserve, inflammatory burden, reduced intake, and physical vulnerability. [8] [9]	Systematic review evidence links olfactory impairment with frailty, but causality is not settled. [9]
Mobility and physical function	Poor olfaction can co-occur with slower mobility decline patterns, physical function deficits, or broader neurological and systemic ageing. [10] [11]	Supports the view that smell can be a functional ageing signal rather than only a sensory symptom. [10]
Cognition and mortality	Olfactory impairment is associated with cognitive ageing, dementia risk, and mortality in cohort studies. [1] [7] [12]	May reflect neurodegeneration, systemic disease burden, environmental exposure, frailty, nutrition, or mixed pathways. [1] [7] [12]

Nutrition, Appetite, and Food Choice

Chemosensory loss can change eating through reduced flavor intensity, weaker appetite cues, altered food reward, reduced dietary variety, and difficulty detecting spoiled foods. A scoping review of taste disorders and malnutrition in older adults found that subjective taste problems were often associated with nutritional intake, malnutrition risk, or unintentional weight loss, while objective taste tests produced more inconsistent associations. [1] [4]

The inconsistency is important. Self-reported taste loss may capture a broader lived experience that includes smell loss, dry mouth, oral discomfort, appetite, medication effects, and illness burden. Objective taste strips may isolate narrower gustatory thresholds, which can be useful but may miss some of the functional burden around meals. [4] [5] [6]

Frailty and Mortality Signals

Olfactory impairment has repeatedly been studied as a marker of later-life vulnerability. In the InCHIANTI study, olfactory dysfunction was associated with frailty, prefrailty, and reduced survival, with inflammatory markers proposed as one possible mediator. [8]

A systematic review and meta-analysis also found an association between olfactory impairment and frailty. This does not mean smell loss directly causes frailty in a simple linear pathway. A more cautious interpretation is that olfactory impairment can mark overlapping processes involving inflammation, nutrition, cognition, physical activity, neurodegeneration, and general physiological reserve. [8] [9]

Mortality studies point in the same direction. In the National Social Life, Health, and Aging Project, olfactory dysfunction predicted five-year mortality among community-dwelling older adults, and later analyses in US adults also reported associations with mortality after adjustment for several measured covariates. These studies support smell as a broad risk marker, not as proof of one isolated causal mechanism. [7] [12]

Cognition, Mobility, and Multisensory Ageing

Olfaction is closely connected to brain systems involved in memory, emotion, and environmental learning. Reviews therefore discuss olfactory impairment in relation to cognitive decline and dementia, while also noting that odor identification tasks can contain sensory, semantic, and memory components. [1] [11]

Olfactory function has also been examined in relation to mobility. A cohort study of older adults reported associations between olfaction and mobility outcomes, which fits a model in which sensory, motor, cognitive, and systemic ageing processes can cluster rather than decline independently. [10]

This clustering is consistent with multisensory ageing research. In the National Social Life, Health, and Aging Project, sensory deficits across taste, smell, vision, hearing, and touch were common and often co-occurred, supporting the idea that chemosensory decline should be interpreted alongside other sensory and functional domains. [3]

Evidence Quality and Interpretation

Confidence is strong that taste and smell often change with age and that these senses connect to nutrition, safety, cognition, quality of life, and broad functional outcomes. This is supported by reviews, population studies, cohort analyses, and systematic reviews across chemosensory ageing. [1] [3] [4] [9]

Confidence is weaker when assigning a precise causal fraction from taste or smell loss to frailty, dementia, mobility decline, malnutrition, or mortality. Many studies are observational, measurement methods differ, and chemosensory loss can be both a contributor to function and a marker of underlying neurodegenerative, inflammatory, metabolic, medication-related, oral-health, or environmental processes. [1] [4] [7] [12]

What This Does Not Mean

It does not mean smell or taste loss is a stand-alone measure of biological age; each can reflect many sensory, neurological, oral, medication, disease, and environmental factors. [1] [5]
It does not mean every association with frailty, dementia, or mortality is directly causal; shared vulnerability and reverse pathways remain plausible. [7] [9] [12]
It does not mean self-reported taste complaints and objective taste thresholds measure the same construct; subjective and objective assessments can capture different parts of the problem. [4]
It does not mean taste and smell should be interpreted apart from other sensory systems, because multisensory impairment is common in older adults. [3]

Practical Interpretation Examples

If appetite declines after smell loss: the pathway may involve reduced flavor intensity, illness burden, medication effects, mood, oral health, or social eating context rather than one isolated sensory mechanism. [1] [4]
If poor olfaction predicts frailty: it may be acting as a marker of broader physiological vulnerability, inflammation, nutrition, cognition, or mobility rather than as a direct cause by itself. [8] [9]
If taste testing looks normal but meals remain difficult: smell loss, saliva, chewing, swallowing, oral pain, dentition, or medication effects may still affect food experience and intake. [4] [5] [6]

Summary

Taste and smell matter for functional ageing because they connect sensory biology with eating, safety, cognition, mobility, frailty, and social life. The strongest interpretation is not that chemosensory decline explains ageing by itself, but that it can act as a meaningful signal within a broader network of sensory, neurological, oral, nutritional, inflammatory, and functional ageing processes. [1] [3] [8] [9]

References

Olofsson, J. K., Ekstrom, I., Larsson, M., & Nordin, S. (2021). Olfaction and aging: a review of the current state of research and future directions. i-Perception. https://journals.sagepub.com/doi/10.1177/20416695211020331
Doty, R. L., & Kamath, V. (2014). The influences of age on olfaction: a review. Frontiers in Psychology. https://pmc.ncbi.nlm.nih.gov/articles/PMC3916729/
Correia, C., Lopez, K. J., Wroblewski, K. E., et al. (2016). Global sensory impairment among older adults in the United States. Journal of the American Geriatrics Society. https://pmc.ncbi.nlm.nih.gov/articles/PMC4808743/
Bauer, S., Blanar, V., Pospichal, J., & Eglseer, D. (2025). Association between taste disorders and malnutrition in older adults: a scoping review. Nutrition Reviews. https://pmc.ncbi.nlm.nih.gov/articles/PMC12793606/
Alves, L. S. M., Munduri, J. M. S., Mattos, M. C. O., Stefani, C. M., & Dame-Teixeira, N. (2024). Changes in taste perception in elderly population and its potential impact on oral health: a systematic review with meta-analysis. Frontiers in Oral Health. https://pubmed.ncbi.nlm.nih.gov/39703868/
Ponzo, V., Bo, M., Favaro, E., et al. (2024). Does presbygeusia really exist? An updated narrative review. Aging Clinical and Experimental Research. https://pmc.ncbi.nlm.nih.gov/articles/PMC10984891/
Pinto, J. M., Wroblewski, K. E., Kern, D. W., Schumm, L. P., & McClintock, M. K. (2014). Olfactory dysfunction predicts 5-year mortality in older adults. PLOS ONE. https://pmc.ncbi.nlm.nih.gov/articles/PMC4182669/
Laudisio, A., Navarini, L., Margiotta, D. P. E., et al. (2019). The association of olfactory dysfunction, frailty, and mortality is mediated by inflammation: results from the InCHIANTI study. Mediators of Inflammation. https://pmc.ncbi.nlm.nih.gov/articles/PMC6402210/
Yeo, B. S. Y., Chan, J. H., Tan, B. K. J., et al. (2024). Olfactory impairment and frailty: a systematic review and meta-analysis. JAMA Otolaryngology-Head & Neck Surgery. https://jamanetwork.com/journals/jamaotolaryngology/fullarticle/2821102
Yuan, Y., Chamberlin, K. W., Li, C., et al. (2024). Olfaction and mobility in older adults. JAMA Otolaryngology-Head & Neck Surgery. https://jamanetwork.com/journals/jamaotolaryngology/fullarticle/2814085
Bothwell, A. R., Resnick, S. M., Ferrucci, L., & Tian, Q. (2023). Associations of olfactory function with brain structural and functional outcomes: a systematic review. Ageing Research Reviews. https://pubmed.ncbi.nlm.nih.gov/37913831/
Choi, J. S., Jang, S. S., Kim, J., Hur, K., Ference, E., & Wrobel, B. (2021). Association between olfactory dysfunction and mortality in US adults. JAMA Otolaryngology-Head & Neck Surgery. https://jamanetwork.com/journals/jamaotolaryngology/fullarticle/2772028

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