What it tells us
That something is wrong, early, cheaply, and without a needle. As a general health signal, smell loss is real and underused.
A canary, not a curiosity
The nose often knows first.
We treat a fading sense of smell as a minor loss — something age, or a cold, simply takes. The data say otherwise. In a large study of older adults, those who could no longer smell were far more likely to die within five years — anosmia outranked heart failure, cancer and lung disease as a predictor. A quiet nose is not a small thing. It is a signal.
An early warning in the brain
Years before the first tremor.
In Parkinson’s disease, the loss of smell often arrives years before the shaking — because the pathology settles early in the olfactory bulb, before it reaches the regions that move the body. In Alzheimer’s, a failing sense of smell predicts the slide from mild forgetfulness to dementia. The diseases reach the nose’s wiring first; the nose reports it first.
A real-time sentinel
Sometimes the only sign.
The world re-learned this in 2020: for many, the first — and sometimes only — sign of COVID-19 was a sudden, total loss of smell. A signal read from the nose, days before anything else, at no cost and no needle. The body had announced the infection in the one language we had stopped listening to.
Why the nose knows first
An exposed, self-renewing sense.
The olfactory system is unusual: among the few parts of the nervous system that regenerate their own neurons, and directly open to the outside air. That makes it a fast, exposed readout — when the body’s capacity to repair and defend falters, this is one of the first places it shows. The sense built to read the world also, quietly, reads us.
Where we draw the line
An honest alarm — not yet a diagnosis.
What it does not
It is non-specific — it flags that, not what — and it is not yet a clinical screen. SHEMIM’s interest is exactly here: turning an honest early signal into one a person can read and act on.
How sure are we?
Every claim, tagged for how settled it is.
Established
- Losing the sense of smell is among the single strongest predictors of death within five years in older adults — outperforming several established risk factors (Pinto et al., 2014).
- Smell loss is one of the earliest signs of Parkinson’s disease, often preceding tremor by years, because the underlying pathology appears early in the olfactory bulb (Doty, 2017).
- An impaired sense of smell predicts progression from mild cognitive impairment to Alzheimer’s; the disease strikes olfactory brain regions early (Roberts et al., 2016).
- Sudden smell loss was frequently the first or only sign of COVID-19 — a real-time olfactory sentinel (Tong et al., 2020).
Documented · early
- The olfactory system is one of the few parts of the nervous system that continually regenerates its own neurons — a fast-turnover, exposed tissue, which is part of why its decline can register broader health changes early.
The honest caveat
- Smell loss is non-specific: it flags that something is wrong, not what. Smell testing is not yet a routine clinical screen. But as a cheap, non-invasive, early signal, it is strikingly underused.
Common questions
Frequently asked.
- What can loss of smell be a sign of?
- Beyond blocked sinuses or a passing infection, persistent loss of smell (anosmia or hyposmia) is an early sign of several serious conditions: it often precedes the motor symptoms of Parkinson’s disease by years (Doty, 2017), predicts progression to Alzheimer’s (Roberts et al., 2016), and is among the strongest predictors of five-year mortality in older adults (Pinto et al., 2014). Sudden smell loss was also a hallmark early sign of COVID-19 (Tong et al., 2020).
- Why does smell loss predict mortality?
- The olfactory system continually regenerates its neurons and is directly exposed to the environment, so a decline in smell can reflect failing regenerative capacity and cumulative damage across the body — making it a sensitive, if non-specific, marker of overall health. In a large study of older adults, anosmia carried roughly four times the five-year mortality of normal smell (Pinto et al., 2014).
- Is smell loss used as a medical test?
- Not yet routinely. Smell testing is cheap and non-invasive, and the evidence linking smell loss to neurodegeneration and mortality is strong, but it is non-specific — it signals that something is wrong, not what — and is not a deployed screening tool. It is, however, widely regarded as underused.
Selected sources
- Pinto et al. (2014), PLOS One — olfactory dysfunction predicts 5-year mortality in older adults.
- Doty (2017), Neuroscience Bulletin — olfactory dysfunction in Parkinson’s disease.
- Roberts et al. (2016), JAMA Neurology — smell impairment and progression to Alzheimer’s / MCI.
- Tong et al. (2020), Otolaryngology–Head and Neck Surgery — anosmia prevalence in COVID-19.
A signal worth learning to read.
If the nose reports the body’s state this early, the work is to listen — carefully, and honestly. That is what SHEMIM studies, marking evidence from inference at every step.