Topic: Brain proteins, microglia and lab models
There has been an increase of interest in olfactory dysfunction since it was realised that anosmia was a common feature of idiopathic Parkinson's disease (PD) and Alzheimer-type dementia (AD). It is an intriguing possibility that the first sign of a disorder hitherto regarded as one of movement or cognition may be that of disturbed smell sense. In this review of PD, parkinsonian syndromes, essential tremor, AD, motor neurone disease (MND) and Huntington's chorea (HC) the following observations are made: 1). olfactory dysfunction is frequent and often severe in PD and AD; 2). normal smell identification in PD is rare and should prompt review of diagnosis unless the patient is female with tremor-dominant disease; 3). anosmia in suspected progressive supranuclear palsy and corticobasal degeneration is atypical and should likewise provoke diagnostic review; 4). hyposmia is an early feature of PD and AD and may precede motor and cognitive signs respectively; 5). subjects with anosmia and one ApoE-4 allele have an approximate 5-fold increased risk of later AD; 6). impaired smell sense is seen in some patients at 50% risk of parkinsonism; 7). smell testing in HC and MND where abnormality may be found, is not likely to be of clinical value; and 8). biopsy of olfactory nasal neurons shows non-specific changes in PD and AD and at present will not aid diagnosis.
Key findings
- In this review of PD, parkinsonian syndromes, essential tremor, AD, motor neurone disease (MND) and Huntington's chorea (HC) the following observations are made: 1). olfactory dysfunction is frequent and often severe in PD and AD; 2). normal smell identification in PD is rare and should prompt review of diagnosis unless the patient is female with tremor-dominant disease; 3). anosmia in suspected progressive supranuclear palsy and corticobasal degeneration is atypical and should likewise provoke diagnostic review; 4). hyposmia is an early feature of PD and AD and may precede motor and cognitive signs respectively; 5). subjects with anosmia and one ApoE-4 allele have an approximate 5-fold increased risk of later AD; 6). impaired smell sense is seen in some patients at 50% risk of parkinsonism; 7). smell testing in HC and MND where abnormality may be found, is not likely to be of clinical value; and 8). biopsy of olfactory nasal neurons shows non-specific changes in PD and AD and at present will not aid diagnosis.
Why it matters
This review notes that smell dysfunction is frequent and often severe in Alzheimer disease and may appear before cognitive signs, and that people with anosmia and one APOE-4 allele have an increased risk of later Alzheimer disease. It is a review of smell testing and does not provide a treatment or cure.
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Study details
- Evidence strengthLow
How this study scored 41/100
Published in a peer-reviewed journal. Scored zero for study design, sample size, effect reported, studied in people and randomised / blinded because the record does not state it. We have no data on institution's track record, so that was left out: it earned 40 of the 97 points we could judge it on, which is 41 out of 100.
| Component | Points | Why |
|---|---|---|
| Journal tier | 7 / 10 | Tier 3 — peer-reviewed journal (Movement disorders : official journal of the Movement Disorder Society) |
| Journal's citation record | 3 / 4 | Movement Disorders: journal h-index 281 (OpenAlex, 2026-10-29) |
| Study design | 0 / 12 | No study design recorded — scores zero, not guessed (not stated in the record — scored 0) |
| Strength of evidence | 1 / 5 | Rated “low” in our summary |
| Peer-review validation | 10 / 10 | Peer-reviewed. Published as an article in a named peer-reviewed journal. |
| How recent | 1 / 5 | 2003 — older than 20 years, still counted |
| Sample size | 0 / 4 | Participant count not stated — scores zero (not stated in the record — scored 0) |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 0 / 3 | Not stated whether this was studied in people — scores zero (not stated in the record — scored 0) |
| Randomised / blinded | 0 / 2 | No randomisation or blinding stated — scores zero (not stated in the record — scored 0) |
| Times cited | 5 / 7 | Cited 290 times (OpenAlex, 2026-10-10) |
| Citations per year | 3 / 5 | 11.6 citations a year over 25 year(s) since 2003 |
| Impact for its field and year | 3 / 6 | Cited 7.0× the average for papers of its field and year (OpenAlex FWCI) |
| Cited by studies here | 2 / 6 | Cited by 3 other studies in this library |
| Still being cited | 1 / 4 | Cited 10 times in 2024–2026 (2026 still in progress; OpenAlex) |
| Senior author's track record | 2 / 4 | Last-listed author Christopher H. Hawkes: h-index 31 (OpenAlex, whole career) |
| Institution's track record | — / 3 | No institution listed in OpenAlex — left out of this score |
| Multi-centre collaboration | 0 / 3 | OpenAlex lists 0 institution(s) in 0 countries — scores zero (affiliation lists can be incomplete) |
| Indexed in PubMed | 2 / 2 | Indexed in PubMed (PMID 12671941) |
| Free to read | 0 / 2 | Behind a paywall — scores zero |
| Points | 40 / 97 | Scored on 19 of 20 parts. We have no data for the rest, so they are left out: 40 of the 97 points we could judge it on is 41 out of 100. |
| Total | 41 / 100 | — |
What each of these 20 components measures, and what this score is not →
Read the original
May need a subscription Unpaywall, Europe PMC and OpenAlex found no free copy of the full text (checked 10 Oct 2026), so the publisher may charge for it. The PubMed abstract is free.
Cite this study APA, Vancouver, BibTeX · download .bib or .ris
Built from the record alzhub holds for this paper, not looked up. Volume, issue and page numbers are not held in the record. Check the citation against the original before you use it.
APA 7th
Hawkes, C. (2003). Olfaction in neurodegenerative disorder. Movement disorders : official journal of the Movement Disorder Society. https://doi.org/10.1002/mds.10379
Vancouver
Hawkes C. Olfaction in neurodegenerative disorder. Movement disorders : official journal of the Movement Disorder Society. 2003. doi:10.1002/mds.10379. PMID: 12671941.
BibTeX
@article{hawkes2003-12671941,
author = {Hawkes, C.},
title = {{Olfaction in neurodegenerative disorder}},
journal = {Movement disorders : official journal of the Movement Disorder Society},
year = {2003},
doi = {10.1002/mds.10379},
pmid = {12671941},
url = {https://doi.org/10.1002/mds.10379}
}
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Referenced by this study and also in the alzhub library, so you can read them here.
Later studies that cite this one
3 studies in the alzhub library list this one in their references.