Introduction
Study | Year | Region | Outcome measures | Olfactory test | Design | n | Mean age, years (SD, if available) | % female | Key findings |
---|---|---|---|---|---|---|---|---|---|
Devanand et al. [10] | 2010 | USA | sMRI, cognitive tests | UPSIT | Cross-sectional | 1092 (802 CN, 120 naMCI, 170 aMCI) | 80.5 (5.8) | 70 | Lower OI associated with lower hippocampal volumes and cognitive test results, but not WMH or entorhinal cortex volumes |
Bahar-Fuchs et al. [9] | 2010 | Australia | Amyloid-PET (PiB) | 6 items from the UPSIT | Cross-sectional | 63 (19 CN, 24 aMCI, 20 AD) | 73.6 | 57 | Higher PiB-PET SUVR associated with lower OI in pooled analyses; however, no relationship found within each cognitive group |
Growdon et al. [5] | 2015 | USA | Amyloid-PET (PiB), sMRI, Cognitive tests (composite) | UPSIT | Cross-sectional | 215 (all CN) | 73.9 (5.9) | 59.1 | Poorer OI associated with lower hippocampal and entorhinal cortex volumes, and cognitive scores. Association with amyloid status at trend level |
Dhilla Albers et al. [6] | 2016 | USA | Amyloid-PET (PiB) (n = 41), sMRI (n = 49) cognitive tests | Two novel olfactory tests | Longitudinal follow-up of cognition | 183 (70 CN, 74 SCD, 29 MCI, 10 AD) | 76.7 | 60.8 | Poor performance associated with lower hippocampal and entorhinal cortex volumes (pooling all cognitive groups) but not with amyloid status; also associated with longitudinal cognitive decline in CN group |
Vassilaki et al. [4] | 2017 | USA | Amyloid-PET (PiB) (n = 306), FDG-PET (n = 305), sMRI (n = 829) | B-SIT | Cross -sectional | 829 (all CN) | 79.2 | 48.5 | Anosmia (B-SIT < 6) (but not hyposmia) associated with abnormal PiB-PET and sMRI measures (hippocampal volume, AD signature CT). Continuous B-SIT scores also associated with sMRI measures |
Risacher et al. [7] | 2017 | USA | Amyloid-PET (florbetapir/ florbetaben); Tau-PET (flortaucipir), sMRI | UPSIT | Cross-sectional | 34 (19 CN, 10 SCD, 5 MCI) | 70.8 | 64.7 | OI not associated with amyloid-PET across sample or any subgroup. Poorer OI associated with tau deposition in the temporal lobe across pooled sample, and in CN plus SCD group. Lower temporal, hippocampal and entorhinal GM volumes across pooled sample |
Heinrich et al. [11] | 2018 | France | sMRI, cognitive tests | B-SIT | Cross-sectional | 75 MCI | 77.1 (6.2) | 74.7 | B-SIT < 8 associated with lower hippocampal volume, higher WMH rating, lower MMSE and FCSRT |
Kriesl et al. [8] | 2018 | USA | Amyloid-PET (PiB), Cognitive tests (composite) | UPSIT | Longitudinal follow-up of cognition | 71 (25 CN, 46 MCI) | 68.5 (7.5) | 58 | UPSIT < 35 had NPV 100%, PPV 41% for binary amyloid status. UPSIT < 35 predicted memory decline in MCI but not CN participants |
Methods
Participants
Olfactory testing
Neuropsychological testing
Imaging
Statistical methods
Results
Percentile | UPSIT score | |||
---|---|---|---|---|
Males | Females | |||
UPSIT: American, age 70–74 (n = 77) | UPSIT: British, age 69–71 (n = 191) | UPSIT: American, age 70–74 (n = 87) | UPSIT: British, age 69–71 (n = 198) | |
99 | 39 | 39 | 40 | 38 |
75 | 34–35 | 35 | 35–36 | 35 |
50 | 29–30 | 32 | 32–33 | 33 |
25 | 24 | 28 | 27–28 | 31 |
Discussion
Normosmia (n = 128) | Hyposmia (n = 251) | pa | Anosmia (n = 10) | pa | |
---|---|---|---|---|---|
Sex, female [n, (%)] | 62 (48.4) | 134 (53.4) | 0.362 | 2 (20.9) | 0.082 |
Age, years [mean, (SD)] | 70.7 (0.62) | 70.6 (0.70) | 0.181 | 70.6 (0.95) | 0.790 |
SEP, manual occupations [n, (%)] | 22 (17.2) | 34 (13.6) | 0.345 | 2 (20.0) | 0.821 |
Current or former smoking [n, (%)] | 80 (62.5) | 166 (66.1) | 0.483 | 6 (60.0) | 0.875 |
Head injury prior to age 69–71 [n, (%)] | 22 (17.2) | 28 (11.2) | 0.101 | 2 (20.0) | 0.821 |
ApoE 4 carrier [n, (%)] | 39 (29.7) | 72 (28.9)b | 0.472 | 4 (40) | 0.495 |
MMSE score [median, (IQR)] | 30 (29–30) | 30 (29–30) | 0.973 | 29.5 (29–30) | 0.565 |
Continuous analyses | Categorical analyses | ||||||||
---|---|---|---|---|---|---|---|---|---|
UPSIT score | Hyposmia | Anosmia | |||||||
β | 95% CI | p | β | 95% CI | p | β | 95% CI | p | |
Associations by linear regression (β coefficient) | |||||||||
Hippocampal volume (mL)b,c | − 0.002 | − 0.004, 0.011 | 0.805 | − 0.075 | − 0.200, 0.050 | 0.239 | − 0.162 | − 0.540, 0.217 | 0.401 |
Entorhinal cortex thickness (mm)a,c | 0.001 | − 0.004, 0.006 | 0.671 | 0.010 | − 0.039, 0.059 | 0.693 | − 0.041 | − 0.191, 0.108 | 0.587 |
Cortical thickness (mm)a | 0.001 | − 0.001, 0.003 | 0.156 | − 0.003 | − 0.022, 0.017 | 0.771 | 0.001 | − 0.058, 0.059 | 0.986 |
Global cognitive score (modified PACC)a | − 0.003 | − 0.017, 0.011 | 0.657 | 0.001 | − 0.141, 0.140 | 0.992 | 0.252 | − 0.172, 0.677 | 0.244 |
Associations by generalised linear model (exponentiated β coefficient) | |||||||||
White matter hyperintensity volume (mL)b,d | 0.992e | 0.967, 1.016 | 0.609 | 1.153e | 0.906, 1.468 | 0.247 | 1.280e | 0.624, 2.628 | 0.501 |