Losing the sense of smell predicts death within five years, according to new research.

As weird as it may sound according to a study published today in the open access journal PLOS ONE, it says that losing your sense of smell strongly predicts death within five years and can act as a marker for exposure to environmental toxins.

The study involved more than 3,000 participants, all of them between 57 and 85 years old, from the National Social Life, Health, and Aging Project (NSHAP), a longitudinal study of factors affecting the well-being of older people living in America.
In 2005-6, Jayant Pinto of the University of Chicago and his colleagues asked all the participants to perform a simple test that involved identifying five common odours (rose, leather, fish, orange, and peppermint), using the number of incorrectly identified odours as a score of the severity of smell loss.

Five years later, the researchers tracked down as many of the same participants as they could, and asked them to perform this smell test a second time. 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.

In other words, those participants who failed the first smell test completely were four times as likely to die within five years than those who correctly identified all five odours. This held true when other factors known to impact smell - such as race, sex, mental illness, and socioeconomic status - were taken into account, and even milder smell loss was associated with slightly increased odds of impending death.

Loss of the sense of smell predicted death more accurately than did a diagnosis of cancer, heart failure or lung disease.

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 odours. Loss of smell may indicate that the body is entering a state of disrepair, and is no longer capable of repairing itself.

The olfactory nerve is also the only part of the nervous system that is exposed to the open air. As such, it offers poisons and pathogens a quick route into the brain, and so losing smell could be an early warning of something that will ultimately cause death.

*Takes a big sniff of the perfume on her wrist*
yeah I'm good for a while yet!

Link and reference

That is interesting, but I imagine that a congenital or genetic defect or chronic condition would get you ruled out of the study. I guess it would be wise to stop and smell the roses, because if you can't smell them anymore, you need to make those end of life plans right away.

a reply to: MichiganSwampBuck

yeah that's true, my partner for one hasn't been able to smell anything for 12 years, due to an operation he had on his nose when he was younger, I'm sure there is plenty more people who haven't had a sense of smell for years due to different conditions/causes.

a reply to: Lady_Tuatha
Interesting. This reminds me of a slightly older article Peanut butter sniff test confirms Alzheimer’s. The time from diagnosis to death varies—as little as 3 or 4 years if the person is older than 80 when diagnosed to as long as 10 or more years if the person is younger.

a reply to: Lady_Tuatha

I see no mention of the strong relationship of smell with taste. So, I 'll offer an alternative explanation to the scientists.

If one starts losing the sense of small/taste, the unconscious systems that rule our bodies are probably no longer capable of maintain the balance, stasis, that if normally has which is completely hidden from us. We all know that the craving for salt drives us toward certain foods even if we don't consciously make the connection, our bodies know what it needs. Same thing for the cravings of a pregnant woman (redundant?. Her body knows what it needs and will kill (more or less) to get that substance.

Shift to older folks. Losing the sense of smell/taste seems to me to be an indication that the bodies auto-craving responses are out of whack and that person, especially being elderly, is not driven to obtain what it should have in their basic nutrition. A complication to that is the elderly frequently do not have the means, physically, financially, or mentally to secure those basic substances (chemicals in foods) that keeps them going. I referring to simple compounds, such as a lack of potassium, iodine, etc. Over a period of time, this lack of basic maintenance allows diseases to get a foothold.

Though this study is likely pointing to some facts it is in no way all encompassing. I just turned 40 and was diagnosed with early onset Parkinsons disease more than 5 years ago. I have a very limited sense of smell for a very long time(it was one of the indicators leading to diagnosis). It is common with this diagnosis to lose or have a limited sense of smell.

I have to admit the thread title got my heart racing a bit. I bet a study of reading that title amongst sufferers points to an increase in heart attacks.

I'm unable to review the links, because I'm currently at work. Is there any data that lists the age of the participants when they died? Could this just be related to age? The average lifespan in America is 78 yrs old so I dunno. Just figured I would ask the obvious questions. I'll review the links later when I have a chance. Interesting article op!

When you are fighting disease, the body uses up the zinc and zinc is also needed for smelling. So a zinc deficiency for many reasons can cause this. People who are fighting something in their body use more zinc. Now autoimmune diseases would also use zinc in their process. Zinc is also a necessary part of the chemical insulin. So energy levels will drop and smell will diminish when you don't have enough zinc.

By supplementing zinc if you have autoimmune issues, it may actually make them worse if you do not avoid the metabolic chemistry that causes the problem. Some foods act as adjuvants that allow improperly digested proteins to enter the bloodstream where they are attacked. If this happens too long imflammation occurs and this can lead to autoimmune issues and soreness in joints.

I totally lost my sense of smell and taste about 25 years ago, it lasted for about two years and then came back.

Well considering the participants of the study were between the age of 50's-80's there no wonder they got those results. They could have substituted smell for anything and still got the same results since most of the participants are nearing the end of there lives.

a reply to: Glassbender777

well no, not really, that doesn't explain why participants who failed the first smell test were four times more likely to die within five years than those who passed the first smell test, also considering that factors such as race, sex, mental illness, and socioeconomic status were all taken into account and the facts remained the same.

originally posted by: Lady_Tuatha
a reply to: Glassbender777

well no, not really, that doesn't explain why participants who failed the first smell test were four times more likely to die within five years than those who passed the first smell test...

Sure, the study you quote says why, and it makes sense.

You have to understand that the sense of smell involves a direct chemical link to the brain. You have chemotactic receptors in your ethmoid plate that go from the top of your nasal passages through the skull to your brain.

That's pretty much the only direct path you get to your brain - the rest are protected by a blood-brain barrier, but your sense of smell relies on an outside chemical input crossing through all the barriers and coming into contact with what amounts to brain tissue.

The nerves in the olfactory bulb die and are turned over pretty often. When you lose your sense of smell, one reason can be that you have reached the end of your telomeres and are no longer replacing cells. That's pretty much the beginning of the end.

Another reason is that diseases that attack the brain often come through the cribriform plate and into your olfactory system. You see a number of toxins, bacteria and/or prions that come through that way, Alzheimer's often starts there, implying that it MIGHT be an outside contaminant that starts it. So, sudden loss of the sense of smell might indicate you just got something up the nose into the brain, or that you are now having an amyloid outbreak that's destroying brain tissue.

I'm worried because I let a fart in my truck yesterday and I didn't smell anything.

What about yearly sinus problems? Maybe that's all it is?

Strange. My mother lost her sense of smell in 1975 due to an unknown virus. She died 22 years later...

So then, that didn't work, did it?

I've never had a quality sense of smell and I'm not dead yet. My mom list her sense of smell like ten years ago because her nose isn't working properly. She recently had her nose forcibly cracked and reset and while it didn't fix her smell it did fix her constant sinus infections.

This 100% seems worth exploring but that it just plain predicts death on its own merit seems too broad.

www.economist.com...

The article which I just linked (which oddly enough was published two days in the future from now) says that they do not include cause of death in the study. So if you lose your sense of smell and get hit by a car then your nose apparently is the first true prophetic.

I've always had a crap sense of smell, but I have a good sense of taste.

My dad worked with anhydrous ammonia for a long time and it burned out his sense of smell, but he's still alive.

hmm...seems like bunk....

my dad can't smell much of anything anymore...been that way for years...he's not dead yet.

my old boss fell off a roof, and hurt his brain..he can't taste OR smell, at all. he's been like that for over a decade....you guessed it, he's still alive...

this is like that pseudo-scientific study that says we yawn because our brains are hot -rolls eyes-