Watch your nose!

Loss of sense of smell indicates risk of death from dementia

Sergey Kolenov, Hi-tech+

In old age, the ability to distinguish odors becomes weaker. A 13-year study by scientists from Sweden and the United States, deterioration of the sense of smell may indicate dangerous age-related diseases and an increased risk of death.

During the study (Liu et al., Relationship Between Poor Olfaction and Mortality Among Community-Living Older Adults: A Cohort Study), volunteers aged 71 to 82 years underwent tests to identify 12 common odors. The experiment started at the turn of the century and lasted for 13 years.

Depending on the number of correct answers, the participants were divided into groups with a "good", "moderate" and "bad" sense of smell. Then the researchers analyzed the causes of death of those of them who did not live to the end of the study.

It turned out that a poor sense of smell increases the risk of death within 10 years by 46%. The trend continued regardless of the gender and race of the participants.

Curiously, the relationship was observed only in those volunteers who were in good health at the time of the study. In their peers already suffering from various diseases, there was no correlation between the sense of smell and the risk of death.

Most often, the inability to distinguish odors was associated with death from dementia and Parkinson's disease. Also, loss of sense of smell may indicate a risk of fatal cardiovascular diseases. There was no connection with death from cancer and respiratory diseases.

Further analysis showed that neurodegenerative diseases account for 22% of the increased risk of death associated with loss of sense of smell.

It is not yet known exactly how the inability to distinguish odors is associated with an increased risk of death. However, there is evidence that in neurodegenerative diseases, this feeling is the first to suffer. Therefore, the authors of the paper propose to include olfactory tests in standard diagnostic protocols. This will help in the early stages to identify such dangerous and so far incurable diseases as Alzheimer's disease and Parkinson's disease. 

Researchers from Sweden have discovered a new indicator of Alzheimer's disease – the NFL protein. When neurons are damaged and die, it penetrates into the blood from the cerebrospinal fluid. Scientists intend to use NFL to evaluate the effectiveness of therapy.

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