Olfactory Decline in Older Adults with Mild Cognitive Impairment with and without Comorbidities

Abstract

Over the past two decades, several studies have measured olfactory performance in Mild Cognitive Impairment (MCI). Deficits are observed in multiple olfactory domains, including odour detection threshold, identification, discrimination, and memory. In this study, the psychophysiological Sniffin’ Sticks smell screening test was administered to examine olfactory functioning in 145 older adults with MCI, a group with MCI and chronic comorbid conditions, and a healthy age-matched comparison group. We hypothesised that olfactory performance will deteriorate in the two MCI groups compared to the control group, even after assessing the known contributions of age and gender. The higher olfactory deterioration in the group with the MCI and the comorbidities in the first year disappeared in the second. This could mean that early consideration of the potential effect of other comorbidities that might affect olfaction should be taken and addressed, as they could easily mask the effect of cognitive decline and/or contribute to it. This study also found higher deterioration in smell identification in participants with MCI, as has been found repeatedly in similar research. Olfactory identification seems to be a more robust marker for discriminating people with MCI and without, and even discriminating between those with MCI and having other health problems.

Olfactory function changes and the predictive performance of the Chinese Smell Identification Test in patients with mild cognitive impairment and Alzheimer's disease

“…Therefore, our study enrolled participants older than 50 years rather than the traditional threshold of 60 or 65 years, so that we could diagnose dementia promptly and treat it at an earlier stage. Several studies proved that olfactory function is affected by age, sex, culture, smoking, depression, and comorbidity (Yahiaoui-Doktor et al, 2019 ; Touliou et al, 2021 ). It has also been reported that there is a general decline in odor identification ability with aging, which accelerates significantly in individuals above 70 years of age (Devanand, 2016 ).…”

Olfactory deficit: a potential functional marker across the Alzheimer’s disease continuum

“…Interestingly, the olfactory activation cortex declines more in the POC and hippocampus during the MCI phase, which may explain the more prominent olfactory deficits than other behavioral and brain volume changes at this stage (Vasavada et al, 2015). Olfactory identification has been reported to be markedly impaired in both aMCI and naMCI (Vyhnalek et al, 2015;Dong et al, 2023), which is a stronger marker for distinguishing patients with MCI from those without, and even MCI from those with other health problems (Touliou and Maglaveras, 2021).…”