Anagen phase question

[meteor]

So this question has been bugging me for a while: why do all sources I've checked (e.g. "Chemical and Physical Behavior of Human Hair" by C.R. Robbins, etc...) claim that anagen (active growth) phase for scalp hair lasts 3-6 years? (They do acknowledge that there are some "exceptions" to this rule though.)

With average growth rate of 6'' per year, it would mean that people wouldn't normally be able to grow longer than 36'', on average, even if they tried.

And yet, anecdotal evidence suggests that people who try to reach terminal (or just grow long hair), tend to get a lot more than 36'' (barring hair-cutting, hair-loss or extensive damage episodes, of course), before hitting terminal length.

Where does such a (presumably) short 3-6 years range even come from? Does anybody know? :)
Thank you! :flower:

[Nique1202]

There were only a couple of extremely small studies done (at least one had only two participants), and all seem to have used very biased populations and bad methodology to study it. More info here (http://blackgirllonghair.com/2012/05/what-is-the-maximum-length-your-hair-will-grow/) which is as deep as I can dig up. Oddly I can't find the studies themselves or any direct references to them.

tl;dr A couple of people with what seem like abnormally short anagen phases were studied, the study's authors quoted it as universal fact, and the rest is history.

I'd love to see a real study done on the subject, but it seems unlikely since even reputable science publications seem to take it as read that it's only up to 6 or 7 years.

[meteor]

^ Thanks a lot, Nique, for this excellent information! :flowers: Yes, I've always been surprised by that range (appears low to me) and how even reputable publications just drop that number like it's universal truth, without actually citing specific evidence for the claim.

(I think part of the reason we don't see studies is that they would be extremely long-term and possibly difficult in terms of planning and compliance. One could, however, study hair length of volunteers who already choose to never cut their hair (e.g. Sikhs, etc) who could submit stats on their hair length, maybe? :hmm:)

[cathair]

I have no idea (helpful I know!), but I have wondered this too. So I am watching with interest. If that were true, my hair would be at terminal right now.

[MsPharaohMoan]

There you go. We should start our own study on the interwebs, asking for people who have never cut their hair to submit length measurements. There could be inaccuracies in length measured of course. Best not to ask people who claim terminal because they could be claiming a false terminal.

[irodaryne]

We could also talk to people on here who start with very, very short hair (about pixie length or even shaved) who aren't cutting it at all about their growth.

[lunasea]

How about people who stopped dying and never cut.

[lapushka]

I think it could be right, but the thing is, you don't shed all of it all-at-once, and that might be key to keeping hair on your head. The numbers to me might be skewed, though. My mom used to tell me that every 7 years your hair and skin "turns over".

[gossamer]

I think it could be right, but the thing is, you don't shed all of it all-at-once, and that might be key to keeping hair on your head. The numbers to me might be skewed, though. My mom used to tell me that every 7 years your hair and skin "turns over".

Yeah, but it's not just about shedding, it's about growth. If I average 6" a year, how is my hair 65" (or more, just quoting length of a recent shed I measured) and still going if it's supposed to stop growing every 7? Even if it stayed on my head longer, like Meteor said, it wouldn't be much longer than 36" or 42".

[Nique1202]

I think it could be right, but the thing is, you don't shed all of it all-at-once, and that might be key to keeping hair on your head. The numbers to me might be skewed, though. My mom used to tell me that every 7 years your hair and skin "turns over".

The problem with this logic is that every individual hair can only grow for the total anagen length anyway. Even if your anagen for every hair on your head is 7 years, then your hair will never get longer than 42 inches with average growth rate, no matter what you try. It doesn't matter what your shed rate is, 42 inches would be the maximum. Considering how many people can make it to 40 inches even with fairly rough treatment, it seems VERY unlikely that 7 years is the maximum anagen period.

Also, if 2-7 were the average we'd see a LOT more people who can't grow past their shoulders or APL, but we don't. Even though the LHC is only for people who like or want long hair, most of us should still follow the most common patterns. 2-7 can't be the correct range for wide sections of the population. It seems far more likely that it's 5 to 10 years for most people.

As for studying, it would be pretty difficult. You can't just measure the hair of someone who's never cut their hair because you don't know their growth rate individually, since it DOES vary so much from person to person (one person might grow 4 inches a year, another might grow 8 inches a year) and there's no way to measure the growth rate if you don't cut the hair first and see how fast it grows back. The easiest way would be to shave a reasonably large patch of hair (a couple of square inches, I'd think) and measure that patch every month and see when it stops gaining length, on several hundred or preferably a couple thousand people from various ethnicities and living in different places. It would take upward of ten years or more to be sure, though, and you'd have to account for damage to the hair and breakage and all that stuff.

[Arctic]

I have wondered about this too, and I don't have any answers.

Maybe the 3-6 years is an avarage, even if it's stated often as universal truth. Some grow longer time, some shorter time. (BTW I often see 7 years mentioned.)

Also, when someone reaches terminal, the hemline is often extremely fairytailed. There might be few hairs that reach, say, knees, yet the bulk, the "visual hemline" might be at waist or TBL. Maybe the recearchers, if they have done any calculations, have calculated the "visual hemline" length and ignored the long races, maybe chalking them up to either being trimmed and broken off at one point or another (even though they arent). I don't know, just a thought. But if I would be a researcher and my subject would have hair at terminal lenght, and the hemline would be like I painted above, I would need to make some decisions about what counts and what doesn't. Would I calculate the 15 longest hairs at knees, or the "visual hemline", where the eye sees the hemline being, or something else.

Like it's already pointed out, the growth rate, the shedding (normal, seasonal and hair loss of some kind), the damage/breakage factor, person's health and levels of good nutrition, genes, age, the individual growth patterns (do the hairs seem to grow evenly or unevenly, and if very unevenly, can the person resist trimming)... and so on, all affect the results of such studies. The subjects would - using a hyberbole - need to be chained in a room for the length of the time their terminal length is, so all damage would be neutralized :D To be honest I have no idea how these kind of research is done - maybe current technology would allow the calculation of terminal length (terminal growth time) even for persons who do trim.

I'm just blathering, I really have no real knowledge.

[lapushka]

The problem with this logic is that every individual hair can only grow for the total anagen length anyway. Even if your anagen for every hair on your head is 7 years, then your hair will never get longer than 42 inches with average growth rate, no matter what you try. It doesn't matter what your shed rate is, 42 inches would be the maximum. Considering how many people can make it to 40 inches even with fairly rough treatment, it seems VERY unlikely that 7 years is the maximum anagen period.

Yes but remember also, we measure differently here, so you'll need to substract about 10-12 inches from the numbers.

[Nique1202]

Yes but remember also, we measure differently here, so you'll need to substract about 10-12 inches from the numbers.

I don't understand what you're saying here. Measuring the LHC way, many many folks make it to 40 inches here from the front hairline, with fairly straight hemlines. If they didn't trim to a blunter hemline, the back sections (especially near the nape) would likely measure 10 or more inches longer than that, and they'd have probably 50+ inch hair by LHC measurement. That would be about 7 years of growth, untrimmed, at average growth rate, measured our way.

Since so many people make it to LHC-measured 40 inches with fairly straight hemlines, even some people who do a lot of damaging stuff (Torrin Paige comes to mind), that seems like a fairly average or low estimate of the anagen period, rather than the upper range.

That's why I say that 5-10 years of growth seems closer to the true range of anagen phase, with outliers on either side (a few people who can only grow for 2-3 years, and a few people who might grow for 15-20 years). But, unless someone does a rigorously controlled scientific study, we have no way to say for certain.

[MeAndTheMaz]

Seems to me that trimming has nothing to do with it. What you're trying to measure is how long a particular hair grow out of your head.

You'd need to pick a patch of head and account for all the follicles. keeping track of when the hair coming out of it is growing, resting, or shedding.

The only way you can get any kind of accurate data would be to catch a new hair growing out of the follicle and see how long it stays growing.

Seems like a big ask to me.

ETA: Really, you're not interested in how long a hair can grow length wise, you're interested in how long it's growing time wise. Because of all the external factors, measuring someone's longest terminal length hair is not going to tell you that.

[Arctic]

I agree trimming has nothing to do with the terminal growth time or the length the hairs reach during that time if untrimmed (and un-broken), but to me, without really knowing how these things are measured and calculated, it's somewhat logical to think the hair would need to be uncut to really see it's length. But I'm sure current research has better methods in its usage.

***

ETA: another thought came to my mind.

Since researches need to be playing with avarages a lot - they really need to, as the variables of human hair growth (and everything that has to do with it) are so varied, they probably need to use the calculated avarage growth (about +/- 1 cm per month) as one variate (not sure if that is a correct term), which will automatically affect the calculated avarage terminal length (as in actual length gained, not terminal growing time).

ETA2: Any of this doesn't really answer the original questions, but what I aimed to put into the words without probably successing is, that perhaps the researched need to rely heavily on all kinds of avarage values, to counter the huge variables there are. And from this all, the oft' stated 3-6 (or 7) years stems from. Maybe?

[bunneh.]

Even if you don't cut hair though it will get damaged and break off so you'd actually be losing length in the long run... I think we can safely assume that every single hair gets damaged/splits/breaks/gets cut off at least once in it's anagen phase.

[pailin]

The trick here is that any good scientific study would have to last maybe 10 years. Very few medical studies do- most are nowhere near that long. We need the hair version of tree-rings, I think.

[Beborani]

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC26947/#!po=13.1579

This paper will answer some questions raised here regarding methodology etc.

[MeAndTheMaz]

Come to think of it. A nearly shaved head would be easier to monitor anagen phase because you can more easily track individual follicles without all these pesky hairs in the way. It really doesn't matter how long a hair grows if you're measuring how long it stays on your head.

If you want to get some idea how long it would otherwise grow to, you can cut it on a regular schedule and save all the pieces to reassemble for a length measurement.

The hard part would be identifying a follicle that's just starting a new anagen phase (then trying to remember which one you're watching over a ten plus year period).

There's always carbon dating. :)

[lapushka]

Come to think of it. A nearly shaved head would be easier to monitor anagen phase because you can more easily track individual follicles without all these pesky hairs in the way. It really doesn't matter how long a hair grows if you're measuring how long it stays on your head.

If you want to get some idea how long it would otherwise grow to, you can cut it on a regular schedule and save all the pieces to reassemble for a length measurement.

The hard part would be identifying a follicle that's just starting a new anagen phase (then trying to remember which one you're watching over a ten plus year period).

There's always carbon dating. :)

You could permanent-dye a certain spot on the head, and monitor that part of the head. Seems like it wouldn't be that easy to do, though - anyone up for it? ;)

[meteor]

Thank you so very much for all your replies, guys! :flowers: It's great stuff!


There you go. We should start our own study on the interwebs, asking for people who have never cut their hair to submit length measurements. There could be inaccuracies in length measured of course. Best not to ask people who claim terminal because they could be claiming a false terminal.

That's right! :D I think, even if these reports aren't enough to provide a specific new range, they might be enough to at least falsify the presumption of 3-6 yrs range.

We do have threads like "what's the longest your hair's ever been?" (http://forums.longhaircommunity.com/showthread.php?t=560 or http://forums.longhaircommunity.com/showthread.php?t=101321) but, obviously, the reports are mostly from people who don't leave their hair completely uncut.


We could also talk to people on here who start with very, very short hair (about pixie length or even shaved) who aren't cutting it at all about their growth.


How about people who stopped dying and never cut.

Sorry, just to clarify :flower:, why start with specifically shaved/pixie hair or once the dying is stopped? (Presumably, the moment one shaves or stops dying hair, lots of hair is in the anagen phase anyway.) I would imagine that just knowing the maximum length one has ever achieved after many years of no trimming (divided by avg growth rate for that individual) should be enough to identify the maximum anagen phase (it wouldn't be as long for all the hairs on the scalp, just for the longest ones, obviously). Or am I missing something?


You could permanent-dye a certain spot on the head, and monitor that part of the head. Seems like it wouldn't be that easy to do, though - anyone up for it? ;)
By the way, I think I'll be able to report back on this in the distant future, since I still have some blonde highlights in my hair (from 2012 and years prior to that) that I don't plan on cutting. And lots of LHCers growing out dye/bleach/henna are in the same boat as me. But I'd imagine anagen phase is way too variable, and it's possible that one might not be able to draw conclusions from tiny samples like that.


I think it could be right, but the thing is, you don't shed all of it all-at-once, and that might be key to keeping hair on your head. The numbers to me might be skewed, though. My mom used to tell me that every 7 years your hair and skin "turns over".

I think Nique and gossamer already gave some excellent information on this, but I just wanted to add:
Even though hair doesn't shed all at once and different hairs are at different phases, once the anagen phase is over, no further growth can be achieved for that specific hair strand, it can't "wait it out" and start growing later, it has to go into telogen and catagen (with no new length gain), just waiting to be shed out, and only after that the anagen can start from scratch again. ;)
Though I've read something weird in "Chemical and Physical Behaviour of Human Hair" (p. 31) about hair that was in the Guinness Book of Records and was over 300 cm long: "because of some condition that probably involves interference with the ability of testosterone to control the anagen-to-telogen cycle, her hair has remained in anagen phase for more than 20 years". There was no reference provided for this though, and I remain skeptical.


ETA: another thought came to my mind.

Since researches need to be playing with avarages a lot - they really need to, as the variables of human hair growth (and everything that has to do with it) are so varied, they probably need to use the calculated avarage growth (about +/- 1 cm per month) as one variate (not sure if that is a correct term), which will automatically affect the calculated avarage terminal length (as in actual length gained, not terminal growing time).

ETA2: Any of this doesn't really answer the original questions, but what I aimed to put into the words without probably successing is, that perhaps the researched need to rely heavily on all kinds of avarage values, to counter the huge variables there are. And from this all, the oft' stated 3-6 (or 7) years stems from. Maybe?

Yes, I wonder about this, too. :agree: The factor of growth rate can be tweaked and would change the results quite a bit.

I would imagine, the distribution of lengths of the anagen phase is a lot wider than the distribution of average growth rates in the population. But if we assume that the avg growth rate range could be as wide as 6'' (+/- 5'') per year, that would still provide a wide range if the model starts with this factor of growth rate driving the length.

So, let's say, somebody grows 11'' per year (though I don't know of anybody who does, but I've seen claims of even double avg growth) instead of the typical 6'' per annum, that would already mean 77'' (= 11'' * 7 yrs) at terminal length, if the person's anagen phase is 7 years.


http://www.ncbi.nlm.nih.gov/pmc/articles/PMC26947/#!po=13.1579

This paper will answer some questions raised here regarding methodology etc.

This looks extremely interesting! :thumbsup: Thanks a lot, Beborani! I must admit, even with lots of coffee and time, I'd probably need someone to dumb it down for me first to fully understand it. :lol: (e.g. why the 5-year intervals in the follicular automaton model or why the assumption of follicles dying after 25 cycles?)


There's always carbon dating. :)

:D Ha-ha! True!

This is all fun stuff to consider!

[lapushka]

By the way, I think I'll be able to report back on this in the distant future, since I still have some blonde highlights in my hair (from 2012 and years prior to that) that I don't plan on cutting. And lots of LHCers growing out dye/bleach/henna are in the same boat as me. But I'd imagine anagen phase is way too variable, and it's possible that one might not be able to draw conclusions from tiny samples like that.

You could give it a shot! :)

[meteor]

^ :D Will do, lapushka! :agree:
(Unless I cut it, of course :oops:)

[irodaryne]

Sorry, just to clarify :flower:, why start with specifically shaved/pixie hair or once the dying is stopped? (Presumably, the moment one shaves or stops dying hair, lots of hair is in the anagen phase anyway.) I would imagine that just knowing the maximum length one has ever achieved after many years of no trimming (divided by avg growth rate for that individual) should be enough to identify the maximum anagen phase (it wouldn't be as long for all the hairs on the scalp, just for the longest ones, obviously). Or am I missing something?

It gives you a visual marker. So like... If you start with a 1" pixie, as your hair grows down you can say "these ends are x-years old." You'd keep tabs of the longest ends as your hair grows out and eventually you can say "these ends are x years old" and then keep an eye out for when it stops growing.

It would work even better if you stop dying on longer hair because as the dyed bit grows down you can stay "I stopped dying x long ago" and when the last bits of dyed hair grows out and is no longer visible in your hair (because of those hairs falling out eventually) finally you can say "my anagen phase is about x years because it took x many years for the dye to grow out.

The only thing is the resting phase. Hair rests for however long between it's anagen phase and when it falls out, just kind of chilling there, doing nothing. So maybe you'd keep tab on when the last of the dyed ends stopped growing longer. (because as your hair grew, the amount of it dyed would slowly dwindle. Especially as you start to hit terminal)

[lapushka]

^ :D Will do, lapushka! :agree:
(Unless I cut it, of course :oops:)

Nooooooooooooo!

[meteor]

^ Thanks a lot, irodaryne! :thumbsup: That makes sense. Kind of makes me wish I'd remembered the exact time of my last highlighting session to keep better track. :doh:

LOL, no worries, lapushka! :D No cutting plans here! (And I sure hope that won't change! ;) )
Thanks so much! :flowers:

[lapushka]

LOL, no worries, lapushka! :D No cutting plans here! (And I sure hope that won't change! ;) )
Thanks so much! :flowers:

*sigh of relief* :D I almost forgot you're in the no trimming challenge. :lol:

[irodaryne]

^ Thanks a lot, irodaryne! :thumbsup: That makes sense. Kind of makes me wish I'd remembered the exact time of my last highlighting session to keep better track. :doh:

LOL, no worries, lapushka! :D No cutting plans here! (And I sure hope that won't change! ;) )
Thanks so much! :flowers:

No problem! If my hair was dyed at all, I would go with that. It was, however, cut to chin on October the... 13th or 23rd. One of the two, I'd have to go look up the exact day but I'm sure I can find it somewhere