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Loss of smell may be an early sign of brain diseases
- FollowingTheDao 3y agoThat makes scents. :) But yeah very very poor sense of smell with olfactory hallucinations and I got a bunch of T2 flares around my bilateral occipital horns so that sounds plausible.
- fragmede 3y agoOne fascinating thing about Covid is that we discovered the loss of smell that it caused wasn't just due to Sars-CoV-2 wreaking havoc in the lungs, but that it got into the brain, and caused damage there.
- FollowingTheDao 3y agoNo, it didn’t get into the brain and cause damage in the brain, it it affected the cells around the olfactory nerves. https://www.forbes.com/sites/williamhaseltine/2022/02/14/losing-the-sense-of-smell-how-covid-19-infection-induces-long-lasting-symptoms/amp/ https://www.forbes.com/sites/williamhaseltine/2022/02/14/los...
- fragmede 3y agoYes, it does. https://www.health.harvard.edu/mind-and-mood/does-covid-19-damage-the-brain https://www.health.harvard.edu/mind-and-mood/does-covid-19-d...
- FollowingTheDao 3y agoI didn’t say Covid does not get in the brain or affect the brain. I was saying that the olfactory issues are not caused by infection in the brain, but rather infecting the nasal passage directly.
- fundad 3y ago[flagged]
- dang 3y agoCould you please stop posting unsubstantive comments and flamebait? You've unfortunately been doing it repeatedly. It's not what this site is for, and destroys what it is for. If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html and taking the intended spirit of the site more to heart, we'd be grateful.
- tptacek 3y agoThis isn't that surprising, is it? Influenza can do the same thing.
- sedatk 3y agoMaybe it's related to the brain damage part: COVID didn't just kill my sense of taste and smell, but changed how I perceived touch too. Touch on my skin felt like I had a thin layer of something on my skin, even my teeth. It went away the same time I recovered my taste and smell. https://twitter.com/esesci/status/1608553863937921025?s=20 https://twitter.com/esesci/status/1608553863937921025?s=20 I didn't notice anything unusual about my hearing though.
- eyegor 3y agoFor myself and several friends who started with poor senses of smell, covid boosted our sense of smell for a brief time after having it. My smell was easily 5x as sensitive for a month after having covid the first time. Now it's back to baseline.
- thinkingemote 3y agoI found that the lack of pollution at the beginning of lockdown increased air quality and my sense of smell became more noticeable and sensitive. Particularly in many walks around gardens and the countryside which was in spring. Or perhaps my perceptions of the smells increased rather than being able to smell more things. Even three years later i've still a good smell sense. I love it. It's possible that I had an early infection that triggered this response.
- jagaerglad 3y agoYes I noticed the same, I had always thought that my hometown had very clean air (which by comparison it has) and that's why I never could smell pollution. After some staying at home during the pandemic, even the clean modern cars that passed every ten minutes or so on the calm suburb road REEKED of burning hydrocarbons. Going near the main road was terrible. Now again I can't smell the cars, the main road feels like clean fresh air (even though there are way more cars) maybe if a small motorbike drives by I can smell it
- Nursie 3y agoInteresting parallel with smoking ... I always had a pretty poor sense of smell, then smoked for a number of years, and for about two weeks after quitting I could smell everything. I didn't know office bathrooms were so bad... And then similarly it went back to baseline.
- washadjeffmad 3y agoThis happens to me when I fast for a period or 3-5 days after becoming ill. For about a week after catching a stomach flu, the world smelled and tasted exactly as I remembered it being when I was a kid.
- omgmajk 3y agoMy father lost his sense of smell due to Covid and it never really came back entirely, he always complains that his food tastes nothing these days.
- Zealotux 3y agoI sympathize, I lost my sense of smell and taste for two months, and almost two years later, coffee still tastes vastly different from what I remember.
- scruple 3y agoI had phantosmia three times following COVID. Cigarette smoke each time. The first time lasted nearly a month and was very intense, with the subsequent instances lasting for shorter intervals and not being as intense. I was worried for a minute there that it was my new normal but I'm happy to report I haven't had any further instances in nearly 2 years. It was wretched.
- oneepic 3y ago> the power of the nose peaks in middle age, around age 40 The more you know. But that also means I (< 40) shouldn't be too paranoid yet.
- flagrant_taco 3y agoIt's also a pretty common side effect of colds, flu's, and sinus infections. [1] I never understood why loss of smell became such a focus with Covid, that symptom wasn't novel and I never found anything definitive studies finding it to be more common with Covid vs the others. [1] https://www.yalemedicine.org/conditions/smell-and-taste-disorders https://www.yalemedicine.org/conditions/smell-and-taste-diso...
- zen928 3y agopaired with diminished taste and continued mentions of potential chronic ongoing fatigue and mental fog, it probably got mentally weighted higher as something to be defensive toward it's a pretty primal human fear to be stripped one by one of your senses, considering it's not as common in other cases of illness VS the sudden worldwide common repeated exposure to covid when in some public places, added on with some general anxiety from covid it's not entirely hard to understand others viewpoints being emotionally skewed
- bhk 3y agoA fact-focused comment with receipts, greeted with downvotes.
- jeremymcanally 3y agoMaybe my experience was different but the lack of smell from COVID was farrrrr more acute and noticeable than I’ve ever had with a sinus infection. It was like the sensation just starkly disappeared rather than diminished. It was really one of the most disconcerting symptoms I had if I’m honest!
- anon-3988 3y agoI lived the first 20 or so years of my early life not knowing about smells. I think I already "knew" that I can't smell but I never really appreciated this about myself. I had always been "immune" to smelly things like animal poo, dead animals or whatever (which is abundant since I lived in a remote area). I think the receptors are there because I do feel weird or "sense" that something is wrong when there's smell (only once they told me about it so maybe its just psychological) but I do feel a "sensation" when something that gives out a strong smell is put close to my nose (like perfume and things like that). However, my brain can't seem to connect which is what. I have no idea what "smelly things" smell like, or what makes a perfume smell "good". So my family would often asked me to dispose of things that really smell or enter a really smelly room and things like that because they thought I am just "stoic" in this sense. I think they first realized that I don't smell is when I was shocked when they said that my coffee smelt nice. They went "Wait, you don't know coffee smell?". I had always faked my responses when people ask about smell and basically gave awkward smile or grief whenever is appropriate lol. It didn't dawned on me until recently that I am missing out on a 1/5 a human experience. It also meant that I am very anxious if I am cleaning up properly (do I smell? did I miss a spot?) Does anyone share the same experience? I wonder how you cope with this issue. I don't have any SO so I don't have a mirror that I can reflect on if the room or myself smell or whatever.
- depereo 3y agoI knew a pair of brothers with no sense of smell. Probably genetic for them.
- teraflop 3y agoI don't have any personal experience with this, but Simon Tatham (creator of the PuTTY SSH client) has written about having anosmia: https://www.chiark.greenend.org.uk/~sgtatham/smell.html https://www.chiark.greenend.org.uk/~sgtatham/smell.html
- naet 3y agoI had a friend who couldn't really smell until he got some kind of olfactory surgery. Before the surgery he felt like maybe he was missing out on some stuff like certain tastes or smell experiences (and he had a similar "immunity" to stinks). After the surgery he could smell to some degree and while it was a novelty he didn't feel like it really opened him up to a whole new set of experiences and was a bit underwhelmed. He was more thankful for the ability to breathe through his nose. I think smell is way less impactful than sight or sound, if that makes you feel any better.
- Baeocystin 3y agoAmong the folks I know, the number who lost their sense of smell in their 30s-40s who later went on to develop some form of dementia is 100%, n=5. Different countries, different cultures and backgrounds, but the common denominator is loss of smell predated their dementia diagnosis by ~20 years,+/-5.
- matheusmoreira 3y agoUnexplained and persistent hyposmia or anosmia is definitely correlated with dementia. Doctors do look for it in practice as it's often an early sign. Precise statistics escape me at the moment.
- ahartmetz 3y agoMy dad could not smell for a few years in his 50s - he has Parkinson's disease now, which started (noticeably) about 20 years later. It seems to be subjectively quite awful (depression-like symptoms, difficulty walking - sports was a big part of his life) but at least I can still talk to him like an adult - it's not a proper dementia.
- magicalhippo 3y agoOn a similar note, I recall this research[1] from some years ago about how loss of smell was a strong predictor of death within 5 years in older people. [1]: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0107541 https://journals.plos.org/plosone/article?id=10.1371/journal...
- rstalledman 3y ago[flagged]
- DoreenMichele 3y agoThe unique relationship between nasal cavity and cranial cavity tissues in anatomy and physiology makes intranasal delivery to the brain feasible. An intranasal delivery provides some drugs with short channels to bypass the blood-brain barrier (BBB), especially for those with fairly low brain concentrations after a routine delivery, thus greatly enhancing the therapeutic effect on brain diseases. https://pubmed.ncbi.nlm.nih.gov/18817519/ https://pubmed.ncbi.nlm.nih.gov/18817519/ https://en.wikipedia.org/wiki/Olfactory_bulb https://en.wikipedia.org/wiki/Olfactory_bulb https://en.wikipedia.org/wiki/Olfactory_nerve https://en.wikipedia.org/wiki/Olfactory_nerve I have heard that the brain kind of sticks out into the sinuses, which may not be technically correct but the illustrations etc above show that there is a uniquely direct connection between the sinuses and brain via nerves that pass through very little tissue at a minimum.
- matheusmoreira 3y agoThe olfactory nerve extends directly from the brain. It is the first cranial nerve pair. https://en.wikipedia.org/wiki/Cranial_nerves https://en.wikipedia.org/wiki/Cranial_nerves The nerve forms a bulb directly above the nasal cavity. That bulb emits many smaller projections through the skull and into the nasal cavity. https://en.wikipedia.org/wiki/Cribriform_plate https://en.wikipedia.org/wiki/Cribriform_plate https://en.wikipedia.org/wiki/Olfactory_foramina https://en.wikipedia.org/wiki/Olfactory_foramina The nerves pass through those holes in the bone which are called olfactory foramina. Foramen means hole and these foramina connect the cranial cavity to the nasal cavity. The paranasal sinuses are nearby structures. The olfactory nerves do not go in there. It's absolutely a fact that the nose is pretty much directly connected to the brain though. The best demonstration of this fact is naegleriasis: https://en.wikipedia.org/wiki/Naegleria_fowleri https://en.wikipedia.org/wiki/Naegleria_fowleri https://en.wikipedia.org/wiki/Naegleriasis https://en.wikipedia.org/wiki/Naegleriasis This thing lives in water. If that water enters your nasal cavity, it will travel via olfactory nerve to your brain where it will proceed to literally eat it.
- ggm 3y agoIt is worth pointing out there are other reasons for loss of smell sensitivity. A lifetime of steroid sprays for hayfever, allergy and rhinitis. So "OMG I can't smell it must be dementia" needs to be modulated through "yea: have you had a lifetime of squirting stuff up your nose" Hence (and other reasons, but this would be one) the MAY in the title.
- lionkor 3y agoIs there a good source I can read about this?
- ck2 3y agoWhat does the opposite of it mean? Where you get extremely heightened sense of smell? Because you know how covid made many people lose their sense of smell, many permanently? It did the reverse to me, it made my sense of smell exponential. I've only read a couple stories of other people having this problem. It's not a good thing. The world smells horrible. Way way before I can even hear the garbage truck I can smell it blocks away. Even if a street is empty early in the morning I can smell when someone has been there recently smoking cigarettes or other. It's like some kind of fight or flight survival instinct or adaptation is triggered by the immune system.
- nextaccountic 3y agoThat's fascinating. I remember reading a book where a woman said her grandmother (who was from a nomadic tribe in Africa) could smell rain from many kilometers away. Is this somewhat similar? Are you living with this for how long? What does your doctor says?
- muxator 3y agoSame effect here, and same bad conclusions about the world's smell. It's like a superpower, only detrimental.
- not2b 3y agoThese days, loss of smell is most likely to be long Covid.
- darkclouds 3y agoBeta Alanine has a propensity to depositing itself in the olfactory bulb, so do we see diseases or malnutrition?
- colordrops 3y agoDo you mean beta amyloid?
- darkclouds 3y agoNo not beta amyloid, but I could have also said carnosine instead of beta alanine, which is why I say, is it malnutrition? "The only study available, which assessed carnosine in the brain of human cadavers, revealed little, if any, carnosine in brain regions other than olfactory bulb" https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0123857 https://journals.plos.org/plosone/article?id=10.1371/journal... "Effects of carnosine on olfactory bulb EEG, evoked potentials and DC potentials" https://pubmed.ncbi.nlm.nih.gov/6254611/ https://pubmed.ncbi.nlm.nih.gov/6254611/ "Carnosine in primary afferents of the olfactory system: an autoradiographic and biochemical study" "Previous in vivo studies have shown that beta-alanine is incorporated specifically into the dipeptide L-carnosine (beta-alanyl-L-histidine)." https://pubmed.ncbi.nlm.nih.gov/6801217/ https://pubmed.ncbi.nlm.nih.gov/6801217/
- colordrops 3y agoI have this strange thing where I can smell better than most around me, but it's very faint and not very detailed. It almost feels like I have a really bad sense of smell, and yet I smell many things that others do not.
- ddmf 3y agoI've lost my smell and a lot of my taste thanks to covid, even after a couple of years it hasn't returned. The strange thing - it started to come back in early February, very slightly, I could smell things I'd not been able to for a while - like cinnamon, or rose. Tested positive for covid a few days later. Once covid tested clear using a lateral flow test my smell went.
- stuff4ben 3y agoThat is fascinating that your sense of smell came back "due to covid" and then went away again. I'm suffering from long covid as well and the loss of probably 50% of my ability to smell. Taste went away at the same time as smell, but it quickly came back within a week. Not so with my sense of smell.
- EGreg 3y agoDidn’t this novel coronavirus bring on loss of smell in many people? Hmm
- hanniabu 3y agoAs someone who has suffered from microbiome issues for years, I'm confident they're looking in the wrong place. I'm sure there's changes happening in the brain, but my bet is it's actually starting in the intestines and caused by a bacteria or bacterial imbalance. I've had a lot of things happen to me from lack of smell, heightened smell, tinnitus, sound sensitivity, memory issues, cognitive decline, changes in skin sensitivity, hair loss, etc. I'm confident all of this seems from my microbiome because the symptoms I'm experiencing shift every few months as I work on treating it and experience improvements and worsen.