Sign of Imminent Death?
Olfaction, the sense of smell, is familiar to most people as one of what we call the “five senses,” a set of sensory systems in the body that help us receive information about the world around us. Therefore, as one of the most ancient of the senses that enables animals to identify basic necessities such as food and mates, as well as attain pleasure, the sense of smell is strongly related to various physiological phenomena and is a strong biomarker – a characteristic that indicates the living condition of an organism. Recently, scientists have discovered that what was once just one of the “five senses” can now be used to predict life expectancy.
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An experiment conducted by Jayant Pinto of the University of Chicago and his coworkers was inspired by their knowledge that olfactory problems are closely related to neurodegenerative diseases including Alzheimer’s and Parkinson’s. Such problems have also been discovered to be identified with shortening telomeres, the caps at the tips of chromosomes, which are closely related to life expectancy.
During the experiment, 3,005 subjects between the age of 57 and 85 participated in a short smell test organized by Dr. Pinto and co-researcher Dr. Martha McClintock. They offered five scented felt-tipped pens — fish, leather, orange, peppermint and rose — to the participants, who were afterwards asked to match images of each of the objects with the samples they had smelled. Participants who made zero to one mistakes were classified as “normosmic,” while those who made two or three mistakes were labeled as “hyposmic,” deficient in their sense of smell, and those with four or more mistakes were “anosmic,” or incapable of smelling. Five years later, 430 of the participants had died — 39% of the anosmics, 19% of the hyposmics and 10% of the normosmics.
Such a high mortality rate in the anosmic population does point to some relationship between a weak sense of smell and a higher chance of death. Even after having adjusted all other possible socioeconomic factors such as age, gender, race and other unmentioned health problems, the trend remained true. To a certain extent, a weakening sense of smell may increase chances of accidents, especially if older adults are unable to identify the smell of burning gasoline, for instance, in the case of a fire; it may also prove to be detrimental to feeble people who are more likely than normosmic people to lose their appetite more frequently.
Certainly, this study does not fully explore the cause of the death of each individual in the experiment, which makes it hard to conclude that weakening olfactory senses is a direct causation of mortality. However, it opens up a new lens through which we can understand the relationship between sensory functions and the prediction of death.