6

votes

Are we meant to sleep much longer in the winter than in the summer?

Answered on August 19, 2014
Created February 08, 2011 at 11:37 PM

In the summer in Boston, the shortest night gets down to under nine hours, whereas winter nights are upwards of fifteen hours.

If we were alive before blackout shades and sleep masks, the duration of evening would effect our sleeping patterns, no?

During the winter, you might go to bed early because the sun sets early, plus it's cold and you'd want to get under a blanket with your warm cave-mate. In the summer, you'd stay awake longer with the longer days, and the rising sun would wake you up after a slumber of perhaps under eight hours.

So dual questions here:

  • Would we naturally sleep longer in the winter (maybe even much much longer, judging by sunset/sunrise patterns!)
  • Would we sleep under eight hours during part of the summer, because of sunlight hitting our eyelids?

Sleep hygiene be damned! I don't think that uniform bedtimes match naturally ebbing and flowing sunrises/sunsets, although they certainly do match modern work schedules :(

535633b57c4a4940d1e913e7a12ee791

(1013)

on April 15, 2011
at 12:19 PM

RobS. I remember reading a history article about this. How before the lightbulb people had a first and second sleep. In the middle of the night people would be active by moonlight or candlelight and then go back to bed for the second sleep. This was normal. Funny how things changed so much, so quickly we need a historian to tell us how it was.

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 10, 2011
at 02:45 PM

Rob- yes, it's adapted for modern living (i.e. allowing one to have dinner with friends around 8pm or have a meeting around then too). jbone- I think the iphone has a sunlight emulator wake-up app. I bought a sleepwatch device a few years ago but for some reason never used it.

82166cc32b6cf26de33b69f58fb583b1

on February 10, 2011
at 09:44 AM

Kamal, isn't that different from the natural pattern described by Wehr, Ekirch, and Jessa Gamble in the TED video linked above by jbone? They describe a natural phenomenon of going to sleep a little after dusk, waking into a prolactin-rich state around midnight, then going back to sleep till dawn.

82166cc32b6cf26de33b69f58fb583b1

on February 10, 2011
at 05:11 AM

Thanks for the links! The TED interview (first link) is very good. At 2:55 she says bimodal sleep in normal under natural conditions. She says high levels of prolactin occur during the midnight wakeful period. This rise in prolactin never occurs during "normal" modern conditions with artificial light. When people experience this natural sleep with its high prolactin levels, they feel more awake during the day than they have ever felt before. This is apparently an important part of our biological inheritence, and we are all deprived of it without knowing our loss.

034c678bff434ab3781e3f1771018af9

(279)

on February 10, 2011
at 04:38 AM

I would wager that all the fancy devices coming out that can connect to your computer or smartphone would help a lot with some N=1 experiments on biphasic sleep.

Aead76beb5fc7b762a6b4ddc234f6051

(15239)

on February 09, 2011
at 09:45 PM

ive heard of those when i lived in dark rainy oregon- ill have to check it out. nothing could be worse than waking up to the abby screaming and my daughter kicking in the woor and flipping the lights on. FML!!

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 05:52 PM

Rob- I did a core sleep of 4.5 or 6 hours in the evening, supplemented with a long "nap" of 1.5 hours after work. I never stuck with it long enough to adjust, unfortunately. Thanks for the link! I'm curious though...it seems like there wouldn't be much to do at night except for huddling around a fire. So maybe a couple people stayed as look-outs against danger at night, and everyone else slept. I should probably read those links to learn more.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 04:09 PM

Kamal, I just found a free article by Ekirch on the web which contains a good deal of material from his book. I linked the article at the end of my answer above. Ekirch cites many dozens of quotations about segmented sleep from literature which suggest that biphasic sleep was universal and taken for granted by everyone. He even quotes the philospher John Lock who wrote, "all men sleep by intervals."

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 06:27 AM

Sorry Kamal, I should have realized that was what you meant. How did you force yourself into biphasic sleep? While I was skimming Pubmed I think (not sure) I noticed some papers on markers (e.g. hormones) that are bimodal. I didn't stop to look at them but maybe they provide some evidence on how universal the tendency is for bimodal sleep.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 06:26 AM

Sorry Kamal, I should have realized that was what you meant. How did you force yourself into biphasic sleep? While I was skimming Pubmed I noticed some papers on markers (e.g. hormones) that are bimodal. I didn't stop to look at them but maybe they provide some evidence on how universal the tendency is for bimodal sleep.

47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 09, 2011
at 05:57 AM

Volume 5: Love and Sex; Volume 6: Internet Etiquette; Volume 7: Interaction with Non-Paleos ....

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 04:57 AM

Sorry Rob, I mis-phrased my comment. I've experimented with biphasic sleep in the past, but have never naturally slept biphasically unless I had the flu or something. My last literature dive was a long time ago, so I'll try to recall if there was another controlled free-sleeping experiment. Maybe there wasn't, but I'll check with our hospital's sleep lab docs if they come by the office. Regardless, I should take a gander at those sources you listed, as the second one directly addresses my question.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 04:31 AM

Kamal, I just did a literature search and as far as I can tell, Wehr's 1992 experiment is the only one that has ever been done on this question. He tested 15 people for 15 weeks and 11 became biphasic. It's possible that if those same people had lived under natural conditions their whole lives, all of them would be biphasic. We don't know. You say that you yourself sometimes sleep biphasically, and then you draw the conclusion that you fall into the category of people who wouldn't sleep biphasically in natural conditions. I would draw the opposite conclusion.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 04:30 AM

I just did a literature search and as far as I can tell, Wehr's 1992 experiment is the only one that has ever been done on this question. He tested 15 people for 15 weeks and 11 became biphasic. It's possible that if those same people had lived under natural conditions their whole lives, all of them would be biphasic. We don't know. You say that you yourself sometimes sleep biphasically, and then you draw the conclusion that you fall into the category of people who wouldn't sleep biphasically in natural conditions. I would draw the opposite conclusion.

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 03:54 AM

Off topic...a paleo compendium/encylopedia type thing would be awesome. Volume 1: Food; Volume 2: Sleep; Volume 3: Posture; Volume 4: Movement, etc. Each are very important, but the first is currently getting all the glory.

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 03:51 AM

Well...that was a pretty good answer. The whole sleep thing is a headscratcher for me, because my parents and their ancestors came from near the equator, and then suddenly moved to the land of long winters. My body is so acclimated to the staying up late routine that I've grown to love being a night owl (but not love being drowsy and sad the next day). As far as how we're SUPPOSED to sleep, maybe this area is rife for experimentation. Steady hours vs varying hours by season, monophasic vs biphasic, etc. I figure diet experimentation went well, it's time to see what's up in other facets.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 03:37 AM

Kamal, I don't think we can conclude anything about natural sleep patterns from our own experiences, since we use artificial light. If you know of any scientific studies that show that only some people (not all) become biphasic with natural light during short days, I would be very curious to see them.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 03:34 AM

Kamal, I would be curious to see references to papers (if you know of any) that show that only some people (not all) become biphasic under natural light conditions.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 03:31 AM

Kamal, do you have a citation that shows that under natural conditions (which are difficult to create today outside a sleep lab), not all people become biphasic?

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 02:29 AM

I have gone through biphasic sleeping periods, and did a little reading back then as well. From what little I understand, biphasic sleep is natural during certain periods (i.e. winter) for certain people. Not all people would naturally adopt a biphasic pattern in the absence of artificial light, and I might be one of them based on how long and luscious my zzzzz's get when I'm not working.

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 01:19 AM

Your kiddos are destined for success--early to bed, early to rise. I'm creeping my sleep up to 9 hours a night, and part of that is going to bed earlier, and maybe catching some sunrises at the same time. Of course, for the average commuter, it's tough to wake up late enough for that. I got one of those NatureBright lights for the morning...have you considered getting one? I can't tell the difference yet, but that's because I'm too rushed in the morning to plug it in.

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 12:26 AM

Or rather, Lights Out

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 08, 2011
at 11:56 PM

Also, this may very well be covered in Light Out, which I haven't read.

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7 Answers

10
82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 01:57 AM

A scientist named Thomas A. Wehr did research in the 1990s to answer this question. He found that under natural conditions, sleep patterns change as night grows longer, but not in the way you imagine.

Wehr discovered that under simulated natural conditions, as night becomes longer, the amount of sleep increases (as you suggest), but sleep also becomes biphasic (also known as bimodal). That means we sleep for a few hours, then wake for a couple of hours, then sleep again for a few hours. In other words, during long nights, people naturally wake in the middle of the night and stay up for a few hours before going back to sleep.

Biphasic sleep is the normal pattern for many animals, and people used to sleep that way in Europe until a few hundred years ago. We know this about Europe from the work of an historian named A. Roger Ekirch. He discovered that European languages used to have terms for the two periods of sleep. In English, the first period of sleep was called "dead sleep" or "first sleep." The second period was called "morning sleep" or "second sleep." These terms were ordinary parts of our language until the industrial revolution, when artificial lighting changed the sleep-wake cycle.

Here is a link to Wehr's original paper on this subject:

Wehr TA. In short photoperiods, human sleep is biphasic. J Sleep Res. 1992 Jun;1(2):103-107.

And here is Ekirch's book about European sleep before the Industrial Revolution:

Ekirch, A. Roger. At Days Close: Night in Times Past (2005). Norton.

Here's an article by Ekirch which formed the basis of his book, and which is availble on the web for free:

Ekirch, A. Roger. Sleep we have lost: pre-industrial slumber in the British Isles. American Historial Review2001 April;106(2).

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 03:31 AM

Kamal, do you have a citation that shows that under natural conditions (which are difficult to create today outside a sleep lab), not all people become biphasic?

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 03:34 AM

Kamal, I would be curious to see references to papers (if you know of any) that show that only some people (not all) become biphasic under natural light conditions.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 04:31 AM

Kamal, I just did a literature search and as far as I can tell, Wehr's 1992 experiment is the only one that has ever been done on this question. He tested 15 people for 15 weeks and 11 became biphasic. It's possible that if those same people had lived under natural conditions their whole lives, all of them would be biphasic. We don't know. You say that you yourself sometimes sleep biphasically, and then you draw the conclusion that you fall into the category of people who wouldn't sleep biphasically in natural conditions. I would draw the opposite conclusion.

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 10, 2011
at 02:45 PM

Rob- yes, it's adapted for modern living (i.e. allowing one to have dinner with friends around 8pm or have a meeting around then too). jbone- I think the iphone has a sunlight emulator wake-up app. I bought a sleepwatch device a few years ago but for some reason never used it.

034c678bff434ab3781e3f1771018af9

(279)

on February 10, 2011
at 04:38 AM

I would wager that all the fancy devices coming out that can connect to your computer or smartphone would help a lot with some N=1 experiments on biphasic sleep.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 06:26 AM

Sorry Kamal, I should have realized that was what you meant. How did you force yourself into biphasic sleep? While I was skimming Pubmed I noticed some papers on markers (e.g. hormones) that are bimodal. I didn't stop to look at them but maybe they provide some evidence on how universal the tendency is for bimodal sleep.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 04:30 AM

I just did a literature search and as far as I can tell, Wehr's 1992 experiment is the only one that has ever been done on this question. He tested 15 people for 15 weeks and 11 became biphasic. It's possible that if those same people had lived under natural conditions their whole lives, all of them would be biphasic. We don't know. You say that you yourself sometimes sleep biphasically, and then you draw the conclusion that you fall into the category of people who wouldn't sleep biphasically in natural conditions. I would draw the opposite conclusion.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 04:09 PM

Kamal, I just found a free article by Ekirch on the web which contains a good deal of material from his book. I linked the article at the end of my answer above. Ekirch cites many dozens of quotations about segmented sleep from literature which suggest that biphasic sleep was universal and taken for granted by everyone. He even quotes the philospher John Lock who wrote, "all men sleep by intervals."

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 02:29 AM

I have gone through biphasic sleeping periods, and did a little reading back then as well. From what little I understand, biphasic sleep is natural during certain periods (i.e. winter) for certain people. Not all people would naturally adopt a biphasic pattern in the absence of artificial light, and I might be one of them based on how long and luscious my zzzzz's get when I'm not working.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 03:37 AM

Kamal, I don't think we can conclude anything about natural sleep patterns from our own experiences, since we use artificial light. If you know of any scientific studies that show that only some people (not all) become biphasic with natural light during short days, I would be very curious to see them.

82166cc32b6cf26de33b69f58fb583b1

on February 09, 2011
at 06:27 AM

Sorry Kamal, I should have realized that was what you meant. How did you force yourself into biphasic sleep? While I was skimming Pubmed I think (not sure) I noticed some papers on markers (e.g. hormones) that are bimodal. I didn't stop to look at them but maybe they provide some evidence on how universal the tendency is for bimodal sleep.

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 04:57 AM

Sorry Rob, I mis-phrased my comment. I've experimented with biphasic sleep in the past, but have never naturally slept biphasically unless I had the flu or something. My last literature dive was a long time ago, so I'll try to recall if there was another controlled free-sleeping experiment. Maybe there wasn't, but I'll check with our hospital's sleep lab docs if they come by the office. Regardless, I should take a gander at those sources you listed, as the second one directly addresses my question.

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 05:52 PM

Rob- I did a core sleep of 4.5 or 6 hours in the evening, supplemented with a long "nap" of 1.5 hours after work. I never stuck with it long enough to adjust, unfortunately. Thanks for the link! I'm curious though...it seems like there wouldn't be much to do at night except for huddling around a fire. So maybe a couple people stayed as look-outs against danger at night, and everyone else slept. I should probably read those links to learn more.

82166cc32b6cf26de33b69f58fb583b1

on February 10, 2011
at 09:44 AM

Kamal, isn't that different from the natural pattern described by Wehr, Ekirch, and Jessa Gamble in the TED video linked above by jbone? They describe a natural phenomenon of going to sleep a little after dusk, waking into a prolactin-rich state around midnight, then going back to sleep till dawn.

535633b57c4a4940d1e913e7a12ee791

(1013)

on April 15, 2011
at 12:19 PM

RobS. I remember reading a history article about this. How before the lightbulb people had a first and second sleep. In the middle of the night people would be active by moonlight or candlelight and then go back to bed for the second sleep. This was normal. Funny how things changed so much, so quickly we need a historian to tell us how it was.

3
47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 09, 2011
at 03:06 AM

Well, Boston is one thing, equatorial Africa is another. And India is yet another (if I may make assumptions from your name and your photograph).

The shortest day in New Delhi, late December: 10 hours, 22 minutes. The longest day, late June: 13:55.

The shortest day in Kolkata, late December: 10:45. The longest day, late June: 13:31.

The shortest day in Chennai (Madras), late December: 11:20. The longest day, late June: 12:55.

The shortest day on the equator, late December: 12 hours. The longest day, late June: 12 hours. (More or less.)

There's my answer. I stopped reading Lights Out: Sleep, Sugar, and Survival because it seemed like a central assumption for the authors was that changes in light and climate from season to season were written into our genes, in a very deep way. But the most important thing is that we have no idea about the extent to which things like this are set in to our bodies, genetically or "epigenetically": if it's only been 60,000-100,000 years since most of us left Africa, then is that long enough to make adherence to seasonal patterns central to my health? I have no idea. I'm not claiming you're making the assumption as problematically as the authors of Lights Out are. But if I were someone of equatorial African origin reading that book I would definitely be scratching my head, wondering if the ideas in it applied to me or not.

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 03:51 AM

Well...that was a pretty good answer. The whole sleep thing is a headscratcher for me, because my parents and their ancestors came from near the equator, and then suddenly moved to the land of long winters. My body is so acclimated to the staying up late routine that I've grown to love being a night owl (but not love being drowsy and sad the next day). As far as how we're SUPPOSED to sleep, maybe this area is rife for experimentation. Steady hours vs varying hours by season, monophasic vs biphasic, etc. I figure diet experimentation went well, it's time to see what's up in other facets.

47a42b6be94caf700fce9509e38bb6a4

(9647)

on February 09, 2011
at 05:57 AM

Volume 5: Love and Sex; Volume 6: Internet Etiquette; Volume 7: Interaction with Non-Paleos ....

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 03:54 AM

Off topic...a paleo compendium/encylopedia type thing would be awesome. Volume 1: Food; Volume 2: Sleep; Volume 3: Posture; Volume 4: Movement, etc. Each are very important, but the first is currently getting all the glory.

2
034c678bff434ab3781e3f1771018af9

(279)

on February 10, 2011
at 04:36 AM

This is a very good question, Kamal!

It made me think of http://www.ted.com/talks/jessa_gamble_how_to_sleep.html It's short and a must view.

And it reminded me that I want to read Jessa Gamble's forthcoming book http://www.amazon.ca/Siesta-Midnight-Sun-Jessa-Gamble/dp/0670065110

Also read "Toward a comparative developmental ecology of human sleep" (2002). http://webdrive.service.emory.edu/groups/research/lchb/PUBLICATIONS%20Worthman/PUBLICATIONS%20CMW%202002/Ecology%20of%20Human%20sleep.pdf It's long but fascinating. There are some major, major differences in how different groups of humans sleep.

I'm writing to add that when I've briefly lived in a village in Western Africa, sleep schedules were all dictated by daylight. It was pretty awesome actually. There really wasn't an option to stay up with lights, because there were just a few solar powered batteries in the village. It was so refreshing not to be bound by the clock.

82166cc32b6cf26de33b69f58fb583b1

on February 10, 2011
at 05:11 AM

Thanks for the links! The TED interview (first link) is very good. At 2:55 she says bimodal sleep in normal under natural conditions. She says high levels of prolactin occur during the midnight wakeful period. This rise in prolactin never occurs during "normal" modern conditions with artificial light. When people experience this natural sleep with its high prolactin levels, they feel more awake during the day than they have ever felt before. This is apparently an important part of our biological inheritence, and we are all deprived of it without knowing our loss.

2
Aead76beb5fc7b762a6b4ddc234f6051

(15239)

on February 09, 2011
at 12:55 AM

im in the boston area, too (cape ann) and winter is hard on me and everyone i know for those reasons. leaving for work in the dark and coming home in the dark is not good for ones mental health and it doesnt take an expert to tell me that.

my kids for some ungodly reason both wake up at 5am. this is often 2+ hours before sunrise in winter, and i want to curl up and die. i cannot for the life of me figure out why they wake up before the sky is even gray, with blackout curtains and white noise int heir rooms, at the SAME. DAMN. TIME. EVER. DAY. when they do it in summer, its much easier for my husband and i to get up with them, but in winter its torture. they also both tend to fall apart and go to bed at 6:30pm in winter, and closer to 8pm in summer. i often wonder if their sleep patterns are more "natural", and (i have such limited experience with this) im pretty sure that the circadian rhythms of young kiddos are more primitive than our own which are so subject to habit and work schedules.

i FEEL like i want to sleep in in the winter, but i feel that to an extent all the time. i FEEL like i want to go to bed earlier when its dark out earlier, but i tend to wrap myself in cashmere and force myself to stay up for true blood. i dont know- i think our sleep habits are so damaged by work, computers, lights, that it would take months of living without electricity out in the wilderness all alone before we could figure out what we should be doing.

the climate here at this longitude is certainly not conducive to long winter nights as there isnt much work to do as far as food gathering, i would imagine. it would make sense that people would conserve energy in the winter until fairly recently when we got all these fancy grocery stores and indoor heat.

Aead76beb5fc7b762a6b4ddc234f6051

(15239)

on February 09, 2011
at 09:45 PM

ive heard of those when i lived in dark rainy oregon- ill have to check it out. nothing could be worse than waking up to the abby screaming and my daughter kicking in the woor and flipping the lights on. FML!!

21fd060d0796fdb8a4a990441e08eae7

(24543)

on February 09, 2011
at 01:19 AM

Your kiddos are destined for success--early to bed, early to rise. I'm creeping my sleep up to 9 hours a night, and part of that is going to bed earlier, and maybe catching some sunrises at the same time. Of course, for the average commuter, it's tough to wake up late enough for that. I got one of those NatureBright lights for the morning...have you considered getting one? I can't tell the difference yet, but that's because I'm too rushed in the morning to plug it in.

0
922038b6c0ca6a051cc4858218931456

(392)

on February 09, 2011
at 04:20 PM

My personal feelings in the winter are that if it's dark out I should be sleeping (well that's how my body feels at least). To be honest, every chance I get in the winter to sleep while it's dark out, I take it. I'm unfortunately always up before the sun rises due to my job, but on weekends I'm up with the sun rising in my window.

I'm sure the lack of sunlight in my cave at work doesn't help much either. The only sun I get is if I can sit outside for lunch or if it is light on the way home. Basically I stay up with the sun in the summer and attempt to go to bed with the lack of it in the winter.

Not scientific but it's what I do. Even when I was in college it's what my body always told me, though obviously then and now other commitments don't allow my body to get all the sleep it thinks it needs.

0
Medium avatar

on February 09, 2011
at 01:59 AM

It's estimated that hominins have been using fire for somewhere between 400,000 & 800,000 years.

0
1acc4ee9381d9a8d998b59915b3f997e

(2099)

on February 09, 2011
at 12:15 AM

I have long thought the same thing, Kamal, and agree with you 100%! I get the feeling that it is our unnatural life-styles that are actually at the root of "Seasonal Affective Disorder" and the depression that so many people...including myself...get at the holidays. p.s. I absolutely hate street lights.

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