Table 4.
Association between Imaging Biomarkers and Impaired Odor Identification in Cognitively Normal Individuals by PiB PET status - the Mayo Clinic Study of Aging.
| Impaired Olfaction | Continuous B-SIT | |||||||
|---|---|---|---|---|---|---|---|---|
|
| ||||||||
| Anosmia vs. normosmiaa | Hyposmia vs. normosmiaa | |||||||
|
| ||||||||
| Imaging Biomarkers | Abn /All | OR (95%CI)b | p | Abn /All | OR (95%CI) | p | slope (95%CI) | p |
| 11C-PiB SUVR>1.40c,d | ||||||||
| 18F-FDG SUVr<1.32c | 17/50 | 3.10 (0.84, 11.52) | .09 | 68/101 | 2.20 (0.81, 5.99) | .12 | −.96 (−1.84, −.08) | .03 |
| AD Sig. CT <2.74 mm | 17/50 | 2.22 (0.59, 8.39) | .24 | 69/102 | 1.31 (0.49, 3.50) | .59 | −.72 (−1.63, .19) | .13 |
| HVa <−2.40 cm3 | 17/50 | 7.15 (1.36, 37.58) | .02 | 69/102 | 1.76 (0.44, 7.05) | .43 | −1.74 (−2.79, −.69) | <.01 |
| 11C-PiB SUVR≤1.40 | ||||||||
| 18F-FDG SUVr<1.32 | 11/80 | 0.12 (0.01, 1.14) | .07 | 107/176 | 0.64 (0.30, 1.36) | .25 | .65 (−.05, 1.34) | .07 |
| AD Sig. CT <2.74 mm | 11/80 | 2.53 (0.59, 10.82) | .21 | 104/173 | 1.15 (0.50, 2.64) | .74 | −.46 (−1.20, .28) | .23 |
| HVa <−2.40 cm3 | 11/80 | 1.41 (0.22, 9.18) | .72 | 104/173 | 1.53 (0.50, 4.69) | .46 | −.29 (−1.24, .66) | .55 |
Osmia categories were defined as follows: anosmia (score <6), hyposmia (men 6–10, women 6–10.25), normosmia (men 10.25–12; women 10.5–12); B-SIT score was calculated as the sum of the correct responses for persons with ≤2 missing responses.
Odds ratios (95% CI) and slopes (95%CI) were retained from multinomial logistic regression and simple linear regression models, respectively, adjusted for age (at B-SIT testing), education, sex. Separate models were run for each neuroimaging biomarker (i.e., each model is represented by one line in the table, having Osmia or continuous B-SIT as the outcome variable) in participants with 11C-PiB SUVR>1.40 and in participants with 11C-PiB SUVR≤1.40.
Abnormal PiB defined as11C-PiB SUVr>1.40.
p=0.017 for the interaction term between abnormal PiB (SUVR) >1.40) and abnormal FDG (SUVr <1.32) in the anosmia vs. normosmia comparison and p=0.061 for the hyposmia vs. normosmia comparison (in the multinomial logistic regression model) and p = 0.004 when B-SIT was used as a continuous outcome (linear regression model). Interaction terms between abnormal PiB and abnormal AD cortical thickness (<2.74 mm) or abnormal hippocampal volume (<−2.40 cm3) did not reach statistical significance.
B-SIT = Brief Smell Identification Test; OR = odds ratio; CI = confidence interval; 11C-PiB PET = Pittsburgh compound B positron emission tomography; SUVR = standardized uptake value ratio; 18F-FDG = 18fluorodeoxyglucose. AD Sig. CT = Alzheimer’s Disease signature cortical thickness; HVa = hippocampal volume adjusted for total intracranial volume;