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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.
Can you smell it? Good, you're healthy.
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.
1. Harvest nose stem cells from homeless people
2. ???
3. Profit!
So you've obviously lost your sense of taste. How long do you suppose you've got to live? :-)
John
Wow, I lost most of my sense of smell over 10 years ago after what my doctors suspect was a virus. I still feel pretty good. I'm in good health with low cholesterol and normal blood pressure. Overall, I feel pretty good for a dea
First off, the original article is open access at PLOS ONE here: http://www.plosone.org/article...
The summary statement, "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", implies several things that are misleading and/or totally untrue.
The tip of the olfactory nerve is the olfactory epithelium, where the olfactory sensory receptor cells are located. The olfactory nerve travels through the cribriform plate, a porous area of skull, where it then synapses with the olfactory bulb. The olfactory bulb has several cell types, and only one of these, inhibitory granule cells, is continually regenerated via neuroblasts migrating along the rostral migratory stream from the sides of the lateral ventricles. These cells are thought to play a role in associative learning and coding of new olfactory cues. The olfactory nerve does not have a capacity for self-renewal, nor do any of the olfactory receptor cells.
Furthermore, there is more than one area where neurons undergo continual self-renewal. The dentate gyrus of the hippocampus also fosters a neurogenic niche, and these new cells have important implications for learning, memory, stress, and emotion that we are just beginning to understand.
Thirdly, we don't really know if neurogenesis in the olfactory bulb has anything at all to do with the observed results because this was not measured in the study, but it is a plausible hypothesis for future study.
As a side note, one of the very intriguing aspects of neurogenesis is that after cortical injuries such as trauma or stroke, neuroblasts from the ventricles migrate toward the lesion, rather than toward the olfactory bulb. These cells are capable of forming electrochemically active synapses at the lesion site and appear to aid in recovery. Unfortunately, astrocytic scarring and inflammation limit the regenerative capacity of these cells - but this is an area of intense research in the field of neurotrauma. My current (undergraduate) research is focused on analyzing the effects of post-injury recovery environment (for rats) on subventricular and hippocampal neurogenesis.
For a good summary on neurogenesis:
http://chuang01.web.wesleyan.e...
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.
Four years ago, I lost my sense of smell. No other physical manifestations. After a month without any smell (quite disconcerting - couldn't smell coffee, food, or anything, Took much of the color out of life), Kaiser hospital did a cat scan of my head and reported a very minor nasal obstruction, probably mucus.
Over the next few months, a weird constellation of symptoms showed up: severe anxiety. Sudden, severe depression. Occasional double vision. Absolute insomnia for four days. Bizarre - in my life, I'd never felt anything like this. (I don't do drugs, alcohol, or have any history of mental troubles)
Then my pee turned black. My wife took me to the hospital...
After sonograms & catscans, the radiologist found a walnut sized tumor on my pancreas.
The doctor looks at me and asks if I have any kids. "Sure, two of 'em," I replied.
"Then you'd better get to an attorney and make your will. Don't waste any time."
Less than 5% of pancreatic cancer patients live for 5 years. After making my will, I had a Whipple operation (don't ask), the surgeon removed the tumor (along with a gall bladder, and god knows what else). I'm still alive today, almost 4 years later, writing Python code and shell scripts. Within my field, I'm moderately well known, so I'm posting this anonymously.
Here's the important part: Pancreatic and other cancers often show strange pro-dromal symtoms, months before the obvious manifestations occur. Things like sudden onset, severe anxiety. depression, and emotional distress. And the sudden loss of smell. Sure, laugh at the postings here. But take it seriously if this happens to you or someone you know.
Loss of smell might just be from a common cold. But it may be a prodromal indicator of something serious.