“Ruane and colleagues1 address a pressing and timely issue: the intersection of olfactory impairment (OI) and aging-related outcomes. [..] The growth in the prevalence of older adults brings substantial societal, economic, and public health implications, making the detection and prevention of risks in this group essential. Olfaction appears to be a unique canary in the coal mine. [..]
At 6 years, dementia emerged as the predominant mediator, accounting for 23% of the OI-mortality association, followed by frailty at 11% and malnutrition at 5%. By 12 years, however, the influence of dementia and malnutrition waned, leaving frailty as the sole significant mediator, responsible for 8% of the association. This temporal shift underscores the potential of OI—particularly in the context of neurodegenerative processes or dietary alterations—to serve as a near-term marker of systemic vulnerability and to enhance the precision of identifying imminent age-related risks in older adults. However, the persistent role of frailty reflects a broader narrative of physiological decline, capturing the trajectory from a state of homeostatic symphony to cacophony.2
[..] OI demonstrates a stronger predictive value for mortality than other sensory impairments and remains significant even after accounting for declines in physical function.4 This sets olfaction apart from other well-recognized sensory impairments linked to dementia and mortality, such as hearing loss, which has garnered substantial funding and is becoming increasingly mainstream in public health initiatives. Meanwhile, olfaction’s distinctive relationship with longevity underscores OI’s potential untapped utility as a sentinel marker of systemic decline, particularly because it imposes minimal physical limitations compared to other sensory losses.
[..] a primary symptom of neurodegenerative disease and dementia is smell loss, which also has clear potential dietary implications, such as malnutrition. Frailty’s role as a mediator over a longer time course, however, warrants focused attention, especially because it is less well understood, and it remains unclear whether OI acts as a biomarker or plays a causative role in this association. Frailty, characterized by diminished strength, endurance, and physiological reserve, is emblematic of aging-related vulnerability. OI’s association with frailty reinforces its position as an indicator of systemic health, suggesting that olfactory assessments could serve as a noninvasive means to identify individuals at risk of progressive decline. [..]
OI’s significance extends beyond frailty, as it intersects with broader systemic and neurological health. While it is well established that OI can serve as an early warning sign for neurodegenerative diseases, its connections to chronic inflammation and cellular aging are equally noteworthy. A conceptual framework for understanding these relationships includes 2 complementary hypotheses. First, OI may reflect systemic processes indicative of underlying disease. Second, it may act as a sentinel marker of cumulative vulnerabilities, creating a feedback loop in which sensory impairments exacerbate physical decline and vice versa. [..] the unique exposure of cranial nerve I to environmental toxins and its direct connection to central nervous system structures further highlights OI’s role as a sensitive indicator of central nervous system health.6 This dual role—serving both as an early marker of neurological disease and as a broader indicator of systemic decline—reinforces the need for routine OI screening as an integral component of holistic geriatric assessments.
[..] While we may not yet be able to intervene directly on OI, addressing associated comorbidities such as depression or malnutrition is both feasible and impactful. Furthermore, neglecting to measure OI does not diminish its importance; without assessing it, we cannot fully understand its intricate relationship with untoward aging-related outcomes. [..]
Measurement of OI is essential, as neglecting to assess it limits our ability to fully understand its intricate relationship with mortality and systemic health. Without standardized testing, these insights remain underexplored.”
Full editorial, NR Rowan, JAMA Otolaryngology – Head & Neck Surgery