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Lost Sense of Smell Is a Strong Predictor of Death Within 5 Years
HughPickens.com writes: Mo Costandi reports at The Guardian that a new study shows losing one's sense of smell strongly predicts death within five years, suggesting that smell may serve as a bellwether for the overall state of the body, or as a marker for exposure to environmental toxins. "Olfactory dysfunction was an independent risk factor for death, stronger than several common causes of death, such as heart failure, lung disease and cancer," the researchers concluded, "indicating that this evolutionarily ancient special sense may signal a key mechanism that affects human longevity." In the study, researchers tested a group of volunteers for their ability to correctly identify various scents. Five years later, they retested as many of the volunteers as they could find.
During the five-year gap between the two tests, 430 of the original participants (or 12.5% of the total number) had died. Of these, 39% who had failed the first smell test died before the second test, compared to 19% of those who had moderate smell loss on the first test, and just 10% of those with a healthy sense of smell. Despite taking issues such as age, nutrition, smoking habits, poverty and overall health into account, researchers found those with the poorest sense of smell were still at greatest risk. The tip of the olfactory nerve, which contains the smell receptors, is the only part of the human nervous system that is continuously regenerated by stem cells. The production of new smell cells declines with age, and this is associated with a gradual reduction in our ability to detect and discriminate odors. Loss of smell may indicate that the body is entering a state of disrepair, and is no longer capable of repairing itself.
During the five-year gap between the two tests, 430 of the original participants (or 12.5% of the total number) had died. Of these, 39% who had failed the first smell test died before the second test, compared to 19% of those who had moderate smell loss on the first test, and just 10% of those with a healthy sense of smell. Despite taking issues such as age, nutrition, smoking habits, poverty and overall health into account, researchers found those with the poorest sense of smell were still at greatest risk. The tip of the olfactory nerve, which contains the smell receptors, is the only part of the human nervous system that is continuously regenerated by stem cells. The production of new smell cells declines with age, and this is associated with a gradual reduction in our ability to detect and discriminate odors. Loss of smell may indicate that the body is entering a state of disrepair, and is no longer capable of repairing itself.
The matter is likely very complex with multiple contributing factors causal and otherwise. Here I've listed a few factors which may have an impact and I'm sure you can find others.
Causal:
1) Smell is very important for our psychological well-being. Simple things like enjoying food and sexual attraction. Suicide is surprisingly common with severe loss of the sense. Even in the absence of suicide, people tend not to live very long if they don't particularly want to.
2) A poor sense of smell may result in eating things that are more toxic or more severely rotten. Even if it doesn't kill you directly, this should place additional strain on the body.
3) On a similar note, you may expose yourself to more harmful bacteria and toxins by touch or inhalation, and be less likely to wash your hands after handling something which doesn't stink (to you).
Not causal:
4) Smell is processed in more primitive parts of the brain than e.g. vision. Loss of the sensation due to neurological damage or degeneration could perhaps be an early indicator of problems in the more immediately vital parts.
If you wait until you stink to wash, you already have issues.