
Sense of smell 'may predict lifespan' - suprgeek
http://www.bbc.com/news/health-29441323
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exratione
Aging is a global phenomenon of damage accumulation throughout the body: more
damage means faster aging. People who show more damage in any one measure tend
to show more damage in all the others too, as it all stems from a few root
causes. This bears up in epidemiological studies, but there is a fair amount
of individual variation.

Almost every decline in aging that can be measured can be correlated with near
future mortality. Grip strength and walking speed are the common ones
presently used, and finding others should be in no way surprising.

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toasted
Agreed.

Also, these types of studies always claim to have corrected for differences in
confounding variables, but there are always more confounding variables than
have been corrected for, and all they end up doing is a statistical comparison
of data with a fewer but still significant number confounding variables, and
if the sample size is big enough they will find a significant P value and try
to imply some sort of causation/significant correlation.

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tokenadult
I like how the article succinctly discussed different possible causal
mechanisms for losing a sense of smell that an individual formerly had as a
marker for declining health and impending death.

This is especially interesting in view of the reduction of sense of smell over
millions of years in the ancestral line of human beings. Before animals in the
clade Primates developed trichromatic color vision, they distinguished fruits
ripe enough to eat from fruits that were not mostly by smell. But after color
vision improved, there was no longer selection pressure to maintain the sense
of smell genes that gave the same information about food plants, and so random
mutations gradually knocked out those genes. Comparative DNA analysis shows
that human beings have descendant genes that were once used for accurate sense
of many smells that human beings can no longer distinguish, but that sensory
capacity was lost by genetic drift until lack of accurate sense of smell for
many substances became fixed in the human population. A fascinating book that
tells this story in more detail is _The Making of the Fittest: DNA and the
Ultimate Forensic Record of Evolution_ by Sean Carroll,[1] a very readable and
enjoyable book about molecular biology studies and the evidence they provide
for biological evolution.

[1] [http://www.amazon.com/Making-Fittest-Ultimate-Forensic-
Evolu...](http://www.amazon.com/Making-Fittest-Ultimate-Forensic-Evolution-
ebook/dp/B001MZ0FHU/)

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uptown
Interesting possible correlation. I have a horrible sense of smell. I always
have. I can certainly smell some things - and particularly strong scents like
coffee, fish, or oranges definitely register, but I'm able to also completely
block out offensive odors in a way that I've found others cannot. I've always
felt that if I had to suffer from a deficiency in a sense, smell is the one to
choose.

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2muchcoffeeman
_The assessment involved identifying distinct odours encased on the tips of
felt-tip pens._

They don't discuss range, just accurate identification. I think I have lost
some range over the years, but not accuracy. Up close I can identify smells
fine.

But sometimes I'll make a cup off coffee, someone will remark how good it
smells, and I can't smell it at all until I'm 30cm from the cup.

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cdjk
Interesting - I don't have a sense of smell (and never have). I don't think
I'm at risk of dying from that, however, barring an undetected gas leak.

Loss of sense of smell is fairly serious, though, so this isn't too
surprising.

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riffraff
you don't have a sense of smell? How is this called? Do you actually never
smell anything or is it just very very weak? Does it also mean that when
eating you basically couldn't tell between smoked herrings and cheese other
than by level of saltiness/texture?

I hope I am not unpolite in asking and please forgive my curiosity, I've never
heard of "congenital olfactive loss" and my mind was just blown.

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cdjk
It's not impolite to ask - I don't mind answering questions about it.
"Congenital Anosmia" is the correct term. It's fairly serious when someone
loses their sense of smell, and can cause weight loss and depression. It can
also be a symptom of some fairly serious conditions (e.g. Parkinson's).

For food - I prefer strong flavors (smoked salmon, capers, onions). Subtle
flavors like spices are lost on me - basil, spinach, and mint all taste the
same. Cheeses can be strong - I think I could tell the difference between blue
cheese and provolone, but I haven't done an experiment. I'll have to try that
sometime.

It is possible I have a very week sense of smell. I can kind of smell coffee,
and there are a few times I've smelled an orange, but that hasn't been
reproducible. My dog got sprayed by a skunk one time, and I couldn't smell
that, so I think it's accurate to say I don't have a sense of smell.

I can "smell" things like vinegar and bleach, but I think that's the
trigeminal nerve. I can't tell the difference between white vinegar and
balsamic vinegar, however.

My mom can't smell either - nor could her dad.

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beachstartup
thanks for sharing, that's super interesting. just one question since you
mentioned salmon and cheeses: do you get the bacon flavor/smell ??? that's a
favorite aroma for a lot of people.

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cdjk
I like bacon, but it's not my favorite food. It's also never triggered what I
think of as a smell, like coffee does sometimes, and oranges have done a
couple times. So I don't think I'm getting any of the aroma.

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Mz
As someone with a history of chronic sinus problems (which were really just
the tip of the iceberg -- an indicator of much more serious problems,
actually), I can well imagine ...a connection here between deteriorating sense
of smell and underlying serious health problems. As my health improves, so
does my sense of smell.

I don't feel like I am saying this very well. Let's try this: If someone goes
blind or has other significant visual impairments, we typically take that
seriously as a big deal and then may look for underlying causes, but the loss
of sense of smell tends to not be treated quite the same way.

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MaysonL
Interesting that "orange" is one of the smells tested: there are at least 3
smells to an orange – the oil in the peel, the juice, and the rind or pith
(the white stuff). Not to speak of the varieties of fish (or do they mean
rotting fish??).

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mrfusion
So maybe dumb question but did they take into account the age of the
participants? That is the older people in the study would tend to has less
sense of smell and die sooner.

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Mz
Yup:

 _And 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._

