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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.
is what so often keeps you out of trouble such as knowing when food has gone bad or you need to wash. From working in a nursing home, I think it is the lack of smell that kills a lot of people. I'm sure the lack of stem cell regeneration hurts, but not knowing when to was your hands or not knowing if food is bad can be a killer for someone with a weak immune system.
Not really happy to read this. Part of my cancer treatment was radiation therapy to the head. I had a severe loss of taste, but smell was nearly intact. With an overly sensitive nose, I guess I was down to what would be a "normal" level. Considering what could have happened (a partial list): loss of sight, loss of hearing, loss of hair, damage to vision, damage to tears, difficulty in swallowing, loss of muscle control of tongue, loss of teeth, loss of smell, inability to chew, and more. Losing taste for a few months was not bad. I ate a lot of Indian food. The problem was eating enough to maintain weight to have the treatment mask fit. Allowable weight variation was zero lbs. I just used a portion control. I am athletic and continued bike miles during treatment. I would do the "french fry" trick in reverse. In a typical diet, you set aside the four fries you are "allowed" to eat, creating a DO NOT EAT pile. I created a somewhat larger pile of YOU MUST EAT THIS. As a conditioned (albeit older athlete) I knew how much to eat to balance calories out with calories in. I was used to being so tired that taste really was never an issue. Tasting takes effort. BTW, taste did come back but still not at 100%. Considering the option -- death -- loss of taste temporarily was OK.
Our sense of smell is the sense running at the lowest level. It's wired straight into the brain in the shortest path of any sense.
This is why the peanut butter smell test can help diagnose Alzheimer's disease. I would expect nontraumatic loss of smell to highly positively correlate with damage to the structures of the temporal lobe (amygdala, basal ganglia, etc). This is where memory lives (in all its forms).
Smell is a pretty raw sense, as opposed to say, vision, which is highly processed by many different cortical systems and areas. I would therefore expect it to yield the best raw cerebral status metadata.