Smell test may be early predictor of dementia, Alzheimer's disease

Odor identification testing may detect cognitive impairment and Alzheimer's disease, according to evidence from two studies presented at the Alzheimer’s Association International Conference.

The studies indicate a potential for improvements in early Alzheimer's detection and management, the researchers concluded.

"It's clear that the science around biological measures in the detection of Alzheimer's continues to gather pace and validation," Heather Snyder, PhD, director of medical and scientific operations for the Alzheimer's Association, said in a press release issued by the organization. "Low-cost, noninvasive measures to detect dementia-related changes and evaluate the risk of future decline continue to be refined and tested; this is a positive step forward to earlier detection and intervention."

Senjoo Lee, PhD, from Columbia University Medical Center, and colleagues evaluated 397 participants with the University of Pennsylvania Smell Identification Test (UPSIT) and MRI. The patients were aged an average of 80 years and represented a multiethnic community cohort who were nondemented at baseline. Participants were followed for 4 years. The researchers measured cortical thickness, cognitive domain scores and cognitive decline.

They reported that 12.6% of participants developed dementia and 19.8% were identified as cognitive decliners during the follow-up period. Entorhinal cortical thickness (HR = 1.5 per 1SD; P = .012) and UPSIT (HR = 1.74 per 1SD; P < .001) both predicted a transition to dementia. UPSIT also predicted cognitive decline (OR = 1.49 per 1SD; P = .005).

In addition, entorhinal thinning was associated with UPSIT in participants who transition to dementia (r = 0.48; P < .0001).

"Our research showed that odor identification impairment, and to a lesser degree entorhinal cortical thickness, were predictors of the transition to dementia," Lee said in the release. "These findings support odor identification as an early predictor, indirectly suggesting that impairment in odor identification may precede thinning in the entorhinal cortex in the early clinical stage of Alzheimer's disease."

In another study, William Kreisl, MD, from Columbia University Medical Center, and colleagues compared the predictive utility of UPSIT with amyloid status, determined by 11C-Pittsburgh Compound B (PIB) brain positron emission tomography (PET) or cerebrospinal fluid (CSF) analysis.

They determined amyloid status and measured UPSIT scores in 81 participants — 55 with amnestic mild cognitive impairment and 26 controls — with an average age of 71 years.

After 6 months of follow up, 67% of participants showed memory decline. Amyloid status predicted decline (OR = 7.31; 95% CI, 1.33-40.23; P = 0.022) and UPSIT score did not (OR = 1.04; 95% CI, 0.94-1.15; P = 0.43), after adjusting for gender, age and education.

Kreisl and colleagues also found that participants with an UPSIT score less than 35 were more likely to have a decline in memory compared with participants with an UPSIT score of 35 or greater (OR = 4.03; 95% CI, 1.03-15.84; P = 0.05).

"Our research suggests that both UPSIT score and amyloid status predict memory decline," Kreisl said in the release. "Younger age, higher education, and shorter follow-up may explain why UPSIT did not predict decline as strongly in this study as in previous studies. While more research is needed, because the UPSIT is much less expensive and easier to administer than PET imaging or lumbar puncture, odor identification testing may prove to be a useful tool in helping physicians counsel patients who are concerned about their risk of memory loss." – by Chelsea Frajerman Pardes

Reference s :

Lee S, et al. Predictive utility of entorhinal cortex thinning and odor identification test for transition to dementia and cognitive decline in an urban community population. Presented at: Alzheimer’s Association International Conference; July 24-28, 2016; Toronto.

Kreisl W, et al. Both odor identification and amyloid status predict memory decline in older adults. Presented at: Alzheimer’s Association International Conference; July 24-28, 2016; Toronto.

Disclosures: Healio Internal Medicine could not confirm relevant financial disclosures at the time of publication.