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Teeth May Reveal a Multi-Day Biological Clock (quantamagazine.org)
117 points by aburan28 on Dec 14, 2016 | hide | past | web | favorite | 21 comments

This was an extremely thought provoking article. I wonder if this same mechanism would also impact activity and cell division rates for cancer cells, with implications both for detecting them via biomarkers and the timing of chemotherapy and radiation treatments designed to attack rapdily growing cells. If you were to time treatment for peak of growth cycle (if there is a five day cycle in humans) it might be much more effective on average (possible 2.5 to 5X depending upon nature and shape of peak).

> This was an extremely thought provoking article.

It is. I keep thinking about an article I once read, maybe ten years ago, about a chinese woman who was 123 years old (according to her own account). The reason she gave why she lived so long was that she used a very strange two daily sleep cycle: she slept only once every two days.

Off coarse this is extremely anecdotal, even if it proves to be true, but I can't stop thinking about a possible connection: what if she grew so old because her slowed down circadian rhythm also slowed down the aging process by slowing down the 7-8 day cell growth cycles?

I'm a big fan of intermittent fasting (regular multiday fasts). I realise that to a man with a hammer, everything looks like a nail, but I wonder if fasting's apparent but as yet mostly unproven (in humans) longevity and health benefits could in some way be related to your interrupted growth cycles idea.

My hypothesis is that intermittent and alternate day fasting are closer to the lifestyle are bodies evolved in so it's less that they have health benefits as much as eating multiple meals a day may be less healthy for you.

In cases like this I'm much inclined to say it's genetics that allow for the sleep cycle and other things than the sleep cycle itself.

Did she sleep longer than a normal once-a-day sleep?

Yes I think it was somewhere between 12 and 16 hours in one go, but I can't remember exactly. And she might had an hour or so of waking somewhere in the middle (like they used to do in the middle ages).

I actually spent a little over a month (a few years ago) sleeping longer periods after two-day awake periods. My days basically looked like:

- Sleep in until noon (~14 hours sleep)

- Pull an all nighter that night

- Go to sleep around 10pm the next day (~34 hours awake)

- Repeat

It had its ups and downs, but the primary reason I stopped is because, while I was able to do more, I felt like a zombie most days (even the first day of the pair) and my work suffered greatly.

I'm a software dev by trade, so I had some luck mitigating the loss of clarity and quickness in thought by structuring my workload where I'd write a suite of tests upfront in the first 4-6 hours after waking up (when I felt the most rested), and then relied on them for correctness while coding for the rest of the 2 days, rather than needing to think through issues. Things still slipped through (because often I was too tired to realize when the tests weren't comprehensive enough), but honestly it was a boon for my test-writing abilities and I think I could have eventually pulled off a decently high quality had I continued.

Eventually I went back to a normal sleeping schedule, and I felt leagues more well-rested each day. My mood increased (well, except when thinking about all the stuff I could be doing if I didn't have to sleep as much) and I generally enjoyed life more on the whole, which is a huge bonus that I don't think I'd trade much for.

It was an interesting experience, and one I've busted out for shorter periods when things at work need a lot of manpower behind a single man, but not something I'd go back to for a long period of time, I think.

What if she lived longer because she took her life easy, having less stress and also having less need to sleep?

It really is fascinating to think of all we might learn about our bodies in the future. This plus stuff like the skull cap tubes that were found make me wonder what other systems we haven't uncovered yet.

Skull cap tubes?


"Researchers Find Missing Link Between the Brain and Immune System" -- https://news.ycombinator.com/item?id=9647253

"New Brain Lymphatic Vessels Drain Old Concepts" -- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4563157/

Thanks for the sourcing. I forgot how much I loved that top quote from the HN comments:

"tl;dr lymphatic nodes go all the way up the back of your brain and into your sinuses. We'd been ripping them out and throwing them away every time we did autopsies or dissections because they were attached to the inside of the skull. Oops."

- @anigbrowl


Wow! Hope you get in touch with the researchers and share your conjecture!

I shared it with folks at Canary Foundation because it also has implications for hunting for biomarkers for cancer.

Just realized that "circadian" comes from circa and dia (so "around a day"?).

Being forced to do Latin and Greek at high school has some benefits after all.

Does it though?

> The term circadian comes from the Latin circa, meaning "around" (or "approximately"), and diēm, meaning "day".

From wikipedia: https://en.wikipedia.org/wiki/Circadian_rhythm

'He named the new biorhythm “Havers-Halberg Oscillation.” The name honors Clopton Havers, who in the late 17th century first described bone lamellae and what would later become known as Retzius stripes, and Franz Halberg, a chronobiologist at the University of Minnesota and a founding father of chronobiology, who died in 2013 at the age of 93.'

Hats off to Dr. Bromage for this. Mark of a pious man.

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