Olfactory, Cognitive Testing Helps Identify Older Adults With Low Dementia Risk

Intact odor identification and global cognition testing performance can highly predict older adults at low risk for dementia, according to findings published in Neurology.

Research suggests that olfactory deficits are correlated with transition to dementia. Conversely, intact olfaction and adequate performance on global cognition testing may predict lack of transition to dementia.

Researchers in the United States conducted a longitudinal cohort study (Health ABC), recruiting 3075 participants aged 70 to 79 at baseline in 1997 and 1998 who lived in Pittsburgh, Pennsylvania or Memphis, Tennessee.  They followed these participants for over a decade.

For this study, only 2240 of these 3075 participants had complete data on olfaction and cognitive status available and were not diagnosed with dementia by year 3 when testing began. Of the 2240 individuals in the analytic sample, 52.7% were women, 63.3% self-identified as White, and 36.7% self-identified as Black. This sample reflected diversity that more closely mirrors the percentages in the current general population of the United States.

In year 3 of the study, the researchers measured olfaction using the 12-item Brief Smell Identification Test (BSIT) with scores ranging from 0 to 12. Scores between 9 and 12 indicated intact olfaction.

During years 1, 3, 5, 7, 9, 10, and 11, the researchers tested global cognition using the Teng Modified Mini-Mental Status Examination (3MS) with scores ranging from 1 to 100. Scores between 78 to 100 indicated intact global cognition.

Additionally, the researchers explored the relationship between olfaction and cognitive test performances and the APOEe4 genotype, which has a known association with dementia risk.

Dementia diagnosis was confirmed via hospital records or records of anti-dementia prescription medications. By the end of the study, 281 individuals (12.5%) were diagnosed with dementia with 131 individuals (5.8%) transitioning to dementia between years 3 and 7. Only 8.8% of individuals with intact olfaction per the BSIT and global cognition per the 3MS transitioned to dementia during the 8-year period between years 3 and 11.

Both impaired odor identification (hazard ratio [HR], 2.29; 95% CI, 1.79-2.94; P <.001) and impaired global cognition (HR, 3.31; 95% CI, 2.26-4.84; P <.001) independently predicted transition to dementia.

Odor identification impairment strongly correlated with transition to dementia for both the 1419 White (HR, 2.45; 95% CI, 1.77-3.38; P <.001) and 821 Black (HR, 2.02; 95% CI, 1.36-3.00; P <.001) participants.

In contrast, global cognition correlated with conversion to dementia only among Black participants (HR, 5.06; 95% CI, 3.18-8.07; P <.001), while APOEe4 genotype correlated with transition to dementia only among White participants (HR, 1.75; 95% CI, 1.20-2.54; P <.01).

Between years 3 and 7, only 2.3% of individuals aged 70 to 75 with intact olfaction and global cognition developed dementia at a conversion rate of 3.8%, while others in this age group with impaired olfaction and cognition converted to dementia at a rate of 25.0%.

The researchers calculated the predictive value for identifying individuals aged 70 to 75 who would transition to dementia over 4 years based on intact olfaction and cognition performance at 0.98.

“Odor identification testing paired with global cognitive testing identified individuals at low risk for transition to dementia in a biracial community cohort,” the researchers wrote. “Identification of such individuals can reduce the need for extensive investigation to establish a diagnosis,” they concluded.

Study limitations included a lack of differentiation between dementia subtypes and lack of biomarker analysis, inability to generalize results to rural populations, and small sample sizes in the subgroups based on age and individual performance scoring, which led to an inability to accurately determine interactions and estimate dementia incidence in each subgroup.

Disclosure: One study author declared affiliations with biotech, pharmaceutical, and/or device companies. Please see original source for full list of disclosures.