Late, but not too late—screening for olfactory dysfunction

April 20, 2018, IOS Press
Credit: University of Duisburg-Essen, Essen, Germany

In a large population-based study of randomly selected participants in Germany, researchers found that participants aged 65-74 years with olfactory dysfunction showed impaired cognitive performance. Interestingly, this strong association was not present in younger (55-64 years) or older (75-86 years) participants. Additionally, the effect was more present in women than men.

In neurodegenerative diseases like Parkinson's and Alzheimer's disease (AD), olfactory function is diminished. Further, precedes the onset of cognitive impairment within AD, which highlights its potential as biomarker for early, preclinical diagnosis. Several studies suggest that olfactory dysfunction predicts progression from normal cognitive functioning to and AD. There is little evidence for this association concerning different age stages and gender differences.

The Heinz Nixdorf Recall (Risk Factors, Evaluation of Coronary Calcium and Lifestyle) study is an observational, population-based, prospective study that examined 4,814 participants (baseline: 45-75 years; 50% men) in the metropolitan Ruhr Area. Participants returned for two examinations every five years. For this analysis, 2,640 participants from the third examination were divided into anosmics (lack of olfactory function), hyposmics (impaired olfactory function) and normosmics (normal olfactory function) according to their Sniffin' Sticks Screening test scores. To examine age- and gender-specific associations, stratified analyses for gender and three were conducted. Men and women differed significantly in their olfactory function. Women had higher scores on the olfactory test. Particularly, middle-aged anosmic male and female participants showed worst performance in several cognitive tests. No associations were seen in younger and older adults. There was a quantitative association in all age groups as anosmics performed worse than hyposmics and hyposmics performed worse than normosmics in all subtests.

The found association in the middle-aged group might occur because this age band between 65-74 years is critical for the onset of age-related cognitive and olfactory decline. Regarding the older age group, the association may be covered by other risk factors occurring in this age band like hypertension, diabetes or coronary artery disease. The pathology potentially causing olfactory and mainly occurs after the age of 65. Thus, the young-aged groups are cognitively healthier and are less often anosmics. This might account for the missing associations in this age . Nevertheless, was reflected by the decrement in olfactory function in all age groups. Participants with worst olfactory function showed worst cognitive performance and vice versa. More distinct effects were found for women compared to men. General differences in olfactory function between men and women can be the cause of this result. At this point we cannot conclude clinical implications regarding gender.

This is the first study reporting on age-specific associations of olfactory function and cognitive performance in the general population. Testing olfactory is an easy and inexpensive way to detect dysfunctions and can help to identify individuals at risk of cognitive decline. Assessing may be an appropriate marker to detect persons at risk of cognitive decline, especially in a crucial age stage between 65 and 74 years.

Explore further: Diabetes mellitus and mild cognitive impairment: Higher risk in middle age?

More information: Sarah Tebrügge et al, Olfactory Function is Associated with Cognitive Performance: Results of the Heinz Nixdorf Recall Study, Journal of Alzheimer's Disease (2018). DOI: 10.3233/JAD-170863

Related Stories

Diabetes mellitus and mild cognitive impairment: Higher risk in middle age?

September 2, 2014
In a large population-based study of randomly selected participants in Germany, researchers found that mild cognitive impairment (MCI) occurred twice more often in individuals diagnosed with diabetes mellitus type 2. Interestingly, ...

Findings could lead to early diagnosis of Alzheimer's

September 26, 2017
Korean researchers have identified the cause of olfactory dysfunction in the early stage of Alzheimer's diseases. It is expected to be used in early diagnosis of Alzheimer's disease and therapeutic research.

New PET imaging technique may help monitor neurological disease progression

January 23, 2017
Olfactory neurons in the nasal cavity are the primary source of our sense of smell. Unlike many types of neurons, olfactory neurons are continuously generated throughout the adult lifespan. This uniquely high rate of neuronal ...

The social costs of smell loss in older women

March 22, 2017
A new study of older U.S. adults conducted by researchers from the Monell Center and collaborating institutions reports that a woman's social life is associated with how well her sense of smell functions. The study found ...

New partnership to study link between olfaction and neurodegenerative disease

May 18, 2016
Deterioration in a person's ability to smell can sometimes be an early sign of neurodegenerative diseases such as Parkinson's or Alzheimer's. Now, researchers at the Monell Center have established a collaboration with the ...

Loss of smell linked to increased risk of early death

March 22, 2017
In a study of adults aged 40 to 90 years who were followed for 10 years, poor smell was linked with an increased risk of dying.

Recommended for you

Researchers identify new genes that may contribute to Alzheimer's disease

August 14, 2018
Researchers from Boston University School of Medicine, working with scientists across the nation on the Alzheimer's Disease Sequencing Project (ADSP), have discovered new genes that will further current understanding of the ...

Deaths from resident-to-resident incidents in dementia offers insights to inform policy

August 14, 2018
Analyzing the incidents between residents in dementia in long-term care homes may hold the key to reducing future fatalities among this vulnerable population, according to new research from the University of Minnesota School ...

Scientists propose a new lead for Alzheimer's research

August 14, 2018
A University of Adelaide-led team of scientists has suggested a potential link between iron in our cells and the rare gene mutations that cause Alzheimer's disease, which could provide new avenues for future research.

Eye conditions provide new lens screening for Alzheimer's disease

August 8, 2018
Alzheimer's disease is difficult to diagnose as well as treat, but researchers now have a promising new screening tool using the window to the brain: the eye.

Potential indicator for the early detection of dementias

August 7, 2018
Researchers at the University of Basel have discovered a factor that could support the early detection of neurodegenerative diseases such as Alzheimer's or Parkinson's. This cytokine is induced by cellular stress reactions ...

pH imbalance in brain cells may contribute to Alzheimer's disease

August 2, 2018
Johns Hopkins Medicine scientists say they have found new evidence in lab-grown mouse brain cells, called astrocytes, that one root of Alzheimer's disease may be a simple imbalance in acid-alkaline—or pH—chemistry inside ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.