Archive for the 'sunlight & sleep' Category

Front Lines of Personal Science: Why Did I Sleep So Well?

Friday, December 20th, 2013

Last night I slept great. I woke up feeling very rested. I can remember only three situations when I woke up feeling more refreshed. (a) On a certain camping trip. (b) When I was on my feet for ten hours. (c) After eating a lot of pork fat. I cannot simulate camping trips, and standing ten hours/day was very hard. The pork-fat effect was repeatable, in the sense that I slept better after eating pork fat, but I never ate that much pork fat again. It was too much.

Why did I sleep so well? I can think of several possible reasons.

1. Random noise. Let’s say there are 20 factors that affect my sleep and they just happened to all line up in a good direction.

Another set of possible reasons derive from what was unusual about yesterday. I can think of five things:

2. I had yogurt and blueberries and honey about 6:30 pm. (In addition to 1 tablespoon honey at bedtime.)

3. I forgot to hang a blackout curtain that darkens my bedroom. Usually I hang two. Last night, by mistake, only one.

4. I started eating dark chocolate daily two days ago. Maybe the good stuff in it (the flavones) accumulates in the brain so that the good effects get larger day by day.

5. I watched faces in the morning a half-hour later than usual. Usually I start watching them at 6:00 am. Yesterday I started at 6:30 am. I had forgotten about this difference until I looked at my records.

6. I switched to a new brand of honey (from a German brand to a Canadian one).

#1 is unlikely. #2 vaguely corresponds to the idea that honey helps us sleep because it supplies energy. Maybe honey at 6:30 fills up the liver (with glycogen) and honey at bedtime goes into the blood. But I’ve eaten plenty of meals at 6:30 without any obvious effect. Maybe they were too low-carb. I don’t know if making my room very very dark (two curtains) is better than making my room dark (one curtain) but there is no obvious reason making my bedroom less dark would improve sleep (#3).  I have never heard anyone say chocolate (#4) improved their sleep. Morning faces did improve sleep but the mood improvement was much more obvious (#5). I’ve tried several brands of honey; there was no obvious difference between them, arguing against #6.

As the day wore on I found myself in a good mood but not a great mood, arguing against #5.

I’d say #2 is the most plausible, the rest less plausible, with #1 the least plausible. But I will test all of them.

More (a day later) I did #3 (only one curtain), #4 (chocolate), #5 (later faces), and #6 (new honey) again. I did not sleep exceptionally well. That makes #1 and #2 more plausible.

Sleep: Summary of What I’ve Learned

Wednesday, December 11th, 2013

I want to summarize what I’ve learned about how to sleep well. I’ve found about a dozen changes that helped. Taken together they suggest the importance of four dimensions:

1. Healthy brain. My sleep greatly improved when I ate a lot of pork fat. (As far as I can tell, butter produced the same effect.) I wasn’t getting enough animal fat. My sleep also improved when I started eating honey at bedtime. I assume honey raised blood sugar to better levels during sleep, improving brain performance. The great importance of this, I believe, is why we evolved preferences that push us to eat strongly sweet foods, such as fruit, separately and later, i.e., dessert. Bedtime honey also caused my muscles to grow more in response to exercise — a sign of better sleep, since muscles grow during sleep. I have never measured the effect of flaxseed/flaxseed oil on my sleep but the brain benefit was so clear in other ways I’d be surprised if it didn’t improve sleep. (more…)

Darker Bedroom Better Sleep

Wednesday, November 27th, 2013

When I moved back to Berkeley from Beijing last spring, I noticed that my sleep was worse in Berkeley, months after arrival. I woke up less rested than in Beijing. There was no obvious explanation. My life was similar in the two places, especially on dimensions that influence sleep. I had expected my health to be better in Berkeley than Beijing because of Beijing pollution.

Wondering why my sleep was different, I realized my Beijing bedroom was probably darker than my Berkeley bedroom. In Beijing I live in an apartment complex and cover most of my bedroom windows to block outside light and for privacy. In Berkeley, I live in a house. My bedroom window looks out over an enclosed backyard. That my Berkeley bedroom might not be dark enough had never occurred to me. It was fairly dark — no street light, no alley light, no light from neighbors.

Did the (likely) difference in darkness contribute to the difference in sleep? I tested this possibility by making my Berkeley bedroom much darker. Later I made it lighter, then darker again (an ABAB design). I measured sleep quality by rating how rested I felt when I woke up on a 0-100 percentage scale where I estimated how rested I felt compared to completely rested (= 100%). I have used this scale for many years. Here are the results:

 photo 2013-11-25effectofbedroomdarknessonsleep_zps2ddcf518.jpeg

To my surprise, when I made my bedroom darker my sleep improved. It got worse when I returned my bedroom to its original darkness. It improved again when I again made it darker. Until I graphed the data, I hadn’t realized that my baseline ratings probably shifted shortly before I made my bedroom darker. (I kept a paper record of my sleep, which made it hard to graph the data. Failure to notice this baseline shift was the last straw….I have gone paperless.) In spite of the baseline problem, the data are convincing that even at low intensities, light intensity mattered.

Depth of sleep (controlled by the amplitude of a circadian rhythm) is surely controlled by the amplitude of the light/dark rhythm. Below a certain threshold of light intensity, however, reducing light at night won’t make a difference. These observations implied that the threshold was lower than I’d thought. Support for the idea that the threshold is low — lower than other people realize, too — comes from a study published last summer after my experiment. Researchers reanalyzed old data to see if there was a correlation between lunar phase and sleep quality. Their subjects had slept in a windowless laboratory room. Nevertheless, sleep was worse during a full moon. One researcher was baffled. “What I can’t get my head around is, what would that cue be?” he said. In other words, how could the phase of the moon influence sleep? I’m not puzzled. The subjects spent only a few nights in the sleep lab. I believe there was carryover from when subjects slept at home, in rooms open to moonlight. Light from a full moon reduced the amplitude of sleep. This affected sleep later in the lab for the same reason jet lag lasts several days.

Is your bedroom dark enough? The light at night in Person X’s bedroom will differ in many ways from the light at night in someone else’s bedroom so a one-size-fits-all rule (your bedroom should be darker than . . . ) makes little sense. What does make sense is personal science: measure your sleep and test different levels of darkness.

Orange Glasses at Night Improve Sleep

Tuesday, November 12th, 2013

After I discovered that morning faces improved my mood, I tried to maximize the effect — determine the the best time, distance, size, and so on. One evening I went to a screening (Taxicab Confessions) at the UC Berkeley journalism school. It started about 7:30 pm and lasted about two hours. Over the next few days, I discovered that the morning-faces effect was gone. It took a few weeks to return. (more…)

David Grimes Responds to Comments

Thursday, July 4th, 2013

In recent posts (here, here, and here), I’ve described the ideas of David Grimes, a British doctor, about the cause of heart disease. Grimes recently responded to comments on the last post:

First, to develop the latitude theme, that distance from the equator determines risk of heart disease, cancers, multiple sclerosis and others. Four visual pieces of evidence for you.

Sunshine_Average_1971-2000_1 (1)

The sunshine map of the UK: We see what would also be the map of multiple sclerosis and CHD in the UK — both diseases most common in the west of scotland and least common in the south-east of England. Similar pattern of average life expectancy.

Look at cancer incidence in North America for another latitude effect.

Then there is breast and colon cancer in Europe:

But the [most] important observation of the sun being protective against cardiovascular disease comes from the USA. A latitude effect is present but weak. However a longitude effect is powerful. It works out as an altitude effect — the higher the altitude of residence the lower the risk of death from cardio-vascular disease (coronary heart disease + stroke). It is interesting to note the mirror image of the land profile from east to west and the CVD death profile. This can be explained most simply and most plausibly by the higher UV exposure at higher altitudes.

This is a powerful supplement to the latitude observations in Europe. The [north-south] length of Europe is worth remembering: the north of Scotland is the same latitude as Hudson Bay. In the north of England I live further north than anywhere in China. This means big sun exposure effects.

The size of the disease differences is impressive — e.g., a factor of 2. I think these sunshine correlations are due either to a protective effect of Vitamin D or a protective effect of sleep (more sunshine = better sleep). There’s no doubt that sleep quality depends on the amplitude of a circadian rhythm (greater amplitude = better sleep), which in turn depends on the amplitude of the sunlight intensity rhythm, the day-night difference.

Heart Disease Epidemic and Latitude Effect: Reconciliation

Friday, June 28th, 2013

For the last half century, heart disease has been the most common cause of death in rich countries — more common than cancer, for example. I recently discussed the observation of David Grimes, a British gastroenterologist, that heart disease has followed an infectious-disease epidemic-like pattern: sharp rise, sharp fall. From 1920 to 1970, heart disease in England  increased by a factor of maybe 100; from a very low level to 500 deaths per 100,000 people per year. From 1970 to 2010, it has decreased by a factor of 10. This pattern cannot be explained by any popular idea about heart disease. For example, dietary or exercise or activity changes cannot explain it. They haven’t changed the right way (way up, way down) at the right time (peaking in 1970). In spite of this ignorance, I have never heard a health expert express doubt about what causes heart disease. This fits with what I learned when I studied myself. What I learned had little correlation with what experts said.

Before the epidemic paper, Grimes wrote a book about heart disease. It stressed the importance of latitude: heart disease is more common at more extreme latitudes. For example, it is more common in Scotland than the south of England. The same correlation can be seen in many data sets and with other diseases, including influenza, variant Creuztfeldt-Jacob disease, multiple sclerosis, Crohn’s disease and other digestive diseases. More extreme latitudes get less sun. Grimes took the importance of latitude to suggest the importance of Vitamin D. Better sleep with more sun is another possible explanation.

The amount of sunlight has changed very little over the last hundred years so it cannot explain the epidemic-like rise and fall of heart disease. I asked Grimes how he reconciled the two sets of findings. He replied:

It took twenty years for me to realize the importance of the sun. I always felt that diet was grossly exaggerated and that victim-blaming was politically and medically convenient – disease was due to the sufferers and it was really up to them to correct their delinquent life-styles. I was brought up and work in the north-west of England, close to Manchester. The population has the shortest life-expectancy in England, Scotland and Northern Ireland even worse. It must be a climate effect. And so on to sunlight. So many parallels from a variety of diseases.

When I wrote my book I was aware of the unexplained decline of CHD deaths and I suggested that the UK Clean Air Act of 1953 might have been the turning point, the effect being after 1970. Cleaning of the air did increase sun exposure but the decline of CHD deaths since 1970 has been so great that there must be more to it than clean air and more sun. At that time I was unaware of the rise of CHD deaths after 1924 and so I was unaware of the obvious epidemic. I now realize that CHD must have been due to an environmental factor, probably biological, and unidentified micro-organism. This is the cause, but the sun, through immune-enhancement, controls the distribution, geographical, social and ethnic. The same applies to many cancers, multiple sclerosis, Crohn’s disease (my main area of clinical activity), and several others. I think this reconciles the sun and a biological epidemic.

He has written three related ebooks: Vitamin D: Evolution and Action, Vitamin D: What It Can Do For Your Baby, and You Will Not Die of a Heart Attack.

Sunlight and Heart Disease

Tuesday, June 18th, 2013

Vitamin D and Cholesterol: The Importance of the Sun (2009) by David Grimes, a British doctor, contains more than a hundred graphs and tables. Most of the book is about heart disease.  Grimes argues that a great deal of heart disease is due to too little Vitamin D, usually due to too little sunlight. I recently blogged about other work by Dr. Grimes — about the rise and fall of heart disease.

Part of the book is about problems with the cholesterol hypothesis (high cholesterol causes heart disease).  One study found that in men aged 56-65, there was no relationship between death rate and cholesterol level over the next thirty years, during which almost all of them died (Figure 29.2). There is a positive correlation between death rate and cholesterol level for younger men (aged 31-39). The same pattern is seen with women, except that women 60 years or older show the “wrong” correlation: women in the lowest quartile of cholesterol level have by far the highest death rate (Figure 29.5). A female friend of mine in England, who is almost 60, was recently told by her doctor that her cholesterol is dangerously high.

The book was inspired by Grimes’ discovery of a correlation between latitude and heart disease: People who lived further north had more heart disease. This association is clear in the UK, for example (Figure 32.4). Controlling for latitude, he found a correlation between hours of sunshine and heart disease rate (Table 32.3): Towns with more sunshine had less heart disease. No doubt you’ve heard that dietary fat causes heart disease. In the famous Seven Countries study, there was indeed a strong correlation between percent calories from fat and heart disease death rate (Figure 30.2). You haven’t heard that in the same study there was a strong correlation between latitude and dietary fat intake (Figure 30.8): People in the north ate more fat than people in the south. The fat-heart disease correlation in that study could easily be due to a connection between latitude and heart disease. The correlation between latitude and heart disease, on the other hand, persists when diet is controlled for.

Grimes convinced me that the latitude/sunshine correlation with heart disease reflects something important. It is large, appears in many different contexts, and has resisted explanation via confounds. Maybe sunshine reduces heart disease by increasing Vitamin D, as Grimes argues, or maybe by improving sleep — the more sunshine you get, the deeper (= better) your sleep. Sleep is enormously important in fighting off infection, and a variety of data suggest that heart disease has a microbial aspect. As long-time readers of this blog know, I take Vitamin D3 at a fixed time (8 am) every morning, thereby improving my Vitamin D status and improving my sleep.

Grimes and his book illustrate my insider/outsider rule: To make progress, you need to be close enough to the subject (enough of an insider) to have a good understanding but far enough away (enough of an outsider) to be able to speak the truth. As a doctor, Grimes is close to the study of disease etiology. However, he’s a gastroenterologist, not a cardiologist or epidemiologist. This allows him to say whatever he wants about the cause of heart disease. He won’t be punished for heretical ideas.

 

Assorted Links

Tuesday, December 4th, 2012

Thanks to Dave Lull and Alex Chernavsky.

Assorted Links

Friday, July 27th, 2012

Thanks to Melody McLaren, Allan Jackson and Bryan Castañeda.

Assorted Links

Monday, March 12th, 2012

Thanks to David Cramer, Jahed Momand and Nancy Evans.

Vitamin D3 and Sleep: More Good News From Primal Girl

Thursday, January 19th, 2012

Late last year, Tara Grant (aka Primal Girl) considered the possibility that taking Vitamin D3 has the same effect as sunlight exposure. For example, taking Vitamin D3 at 7 pm is like getting sunlight at 7 pm. This idea — with my advice about how to sleep well (get an hour of sunlight first thing in the morning) ringing in her ears – led her to try to improve her sleep by taking Vitamin D3 first thing in the morning. It worked:

I usually took my supplements mid-afternoon. I vowed to take them first thing every morning. If I forgot, I would not take the Vitamin D at all that day. I tried it the next day and that night I slept like a rock. And the next night. And the next. Days I forgot and skipped the D3, I still slept great. That was the only change I made to my lifestyle and my sleep issues completely resolved.

I called this “a stunning discovery” and have blogged about it several times. I recently asked Tara for details and an update. She replied:

I am so happy to hear that 1) other people didn’t make the connection easily so I’m not a little slow and that 2) there seems to be something to my discovery. :) I’ve had a few comments from people who have said it has worked for them too. So let me answer your questions:

[What type of Vitamin D3 do you take?]

I take Trader Joe’s brand of Vitamin D3, which is a 1000 IU gelcap, in olive oil. 180 capsules for $4.99. Best deal I’ve found. I tried the tablets years ago and they had no affect on me (even on 8000 units a day plus tanning twice a week my blood levels were only at 58.)

[Has your sleep remained solid?]

My sleep HAS remained solid. I have not had ONE night of bad sleep since I started paying attention to when I was taking my Vitamin D.

[How much do you take?]

I was initially taking 10,000 units a day. After about 2 months, I cut that back to 5000 units to see if there was a difference. I did not wake up quite as rested, but I still slept soundly through the night. On days that I increase my dosage, I sleep better, deeper and feel more rested the following morning. I’ve tried this several times, even when I’ve been spending the night away from home, and it has made a difference. I have also tried eating sugar shortly before bedtime and caffeine in the afternoon (both things that would always make my sleep restless in the past) and I still sleep well!! I’ve also thrown exercising into the mix to see if it makes a difference but it doesn’t change the quality of my sleep – it just makes me tired earlier in the evening. I continue to change my dosage randomly and monitor the results.

Sleep, Mood, Restless Legs and ADHD Improved By Internet Research

Monday, December 19th, 2011

At the SLD forums, Anima describes using several  safe cheap treatments to improve his mood and sleep. First, he tried wearing blue blocker (amber) glasses in the evening. They made him fall asleep more easily and reduced or eliminated hypomania. However, he was still depressed. Second, he tried getting twenty minutes of sunlight early in the morning. His mood improved. But he still had trouble synchronizing his sleep/wake cycle with the sun — that is, being awake during the day and asleep at night. He would stay up an hour later every night and wake up an hour later every day, meaning that half the time he was asleep during the day and awake at night. Finally, he tried adjusting when he ate:

I recently found the missing key to this: meal timing.  I saw a talk that Seth gave where he talked about curing his problem with waking too early by skipping breakfast.  My problem was difficulty waking.  I read an article that suggested that our circadian rhythms are not just tied to light, but to food times as well.  I used to eat late at night and never eat breakfast.  I started eating breakfast immediately upon waking (ick) and stopping all food at least 12 hours before I wanted to wake.  Basically, I did what Seth did only opposite.  It worked. . . . I was even able to adjust my cat’s circadian rhythm — he used to wake me up too early for his breakfast — by gradually moving his supper time.

In another post he describes using B vitamins to treat his restless legs syndrome and ADHD:

I have been taking a supplement with all the B vitamins in amounts much higher than typically recommended. I have also been taking Epsom salt baths for magnesium. I have not experienced restless legs AT ALL since starting. This is quite remarkable to me, because it was such a problem. My ADHD is also much improved.

The idea of treating restless legs syndrome with niacin (a B vitamin) came from Dennis Mangan. Anima had noticed that ADHD and restless legs syndrome often occur together.

He makes some reasonable comments about psychiatrists:

Why are psychiatrists still acting like neurological problems exist in isolation, when clearly they are all related? [In the sense that you can use what is known about how to cure Problem X to help you cure Problem Y, if X and Y often occur together.] I used to take Lamictal, Depakote, Adderall and Ambien every day. That doesn’t include all the meds I tried that didn’t work. I’m currently wearing amber glasses at night and taking a B complex, flax oil (SLD-style) and bathing in epsom salts three times a week. My mood is more stable than it was on medication, and my ADHD is controlled about the same. My sleep is much better. My psychiatrist told me that I would be on medication for the rest of my life. When I told him that I was using dark therapy and light therapy and had stopped taking my medication, he told me that I was “playing with fire,” and that I would end up in a mental institution or commit suicide if I didn’t resume my medication, despite the fact that I had stopped taking it for longer than it would be effective. I asked him if he had read the research on dark therapy. He hadn’t, but he assured me that it is pseudoscience. I guess the definition of “pseudoscience” is any treatment that doesn’t make him money. I puckishly asked him if I seemed manic or depressed, and he was forced to admit that I did not.

The ability of this psychiatrist to ignore contradictory evidence in front of him resembles what happened to Reid Kimball. He told a UCSF gastroenterologist that he was successfully managing his Crohn’s with diet. In my experience, Crohn’s can’t be managed with diet, the doctor said at the end of the appointment.

Vitamin D, Sunlight, and Sleep: More

Thursday, November 3rd, 2011

In the comments on yesterday’s post  (“Can Vitamin D Replace Sunlight? A Stunning Discovery”), two commenters (John and Aaron Blaisdell) noted that Nephropal had said something similar. They’re right. Here’s what Nephropal said in 2009:

Vitamin D taken at night causes insomnia. This is a complaint of a few of my patients. Moreover, when they switch to morning dosing, the insomnia subsides. Thus, Vitamin D should be taken in the morning.

That’s a great observation,  but not the same as Primal Girl’s. Here is her observation, shortened for clarity:

 I usually took my supplements mid-afternoon. I vowed to take them first thing every morning. I tried it the next day and that night I slept like a rock. And the next night. And the next.

The two observations support each other. Both support the idea that the timing of Vitamin D matters. But there are also big differences. Paleo Girl had been taking her Vitamin D in mid-afternoon, not at night. She shifted to first thing in the morning, which is more specific than morning. I changed the title of yesterday’s title to make clearer what is new here: the idea that Vitamin D can substitute for sunlight.

Lots of things cause insomnia if you take them in the evening. Caffeine and other stimulants, for example. A comment on yesterday’s post said that B vitamins and calcium cause insomnia if taken in the evening. This is why Nephropal’s observation, although very important, is not a stunning surprise. You stop taking X in the evening, your sleep improves — I won’t be astonished, no matter what X is.

Vitamin D is not a stimulant or is at best a mild stimulant. Taking Vitamin D in the afternoon should not cause trouble sleeping. Yet Primal Girl had trouble sleeping. And she was getting little morning sunlight. It is a real insight that first-thing-in-the-morning Vitamin D could have the same effect as first-thing-in-the-morning sunlight — in other words, could substitute for missing sunlight. Against all odds, the results supported this idea.

One commenter on yesterday’s post said Primal Girl’s results were both unproven and obvious. Vitamin D is technically a hormone! Melatonin is a hormone, said the comment. I have not heard anyone propose taking melatonin first thing in the morning to improve sleep. It is standard to take melatonin in the evening. The accepted view among circadian rhythm researchers is that sunlight produces its effects on circadian rhythms via nerves, not blood. For example, hundreds of experiments have found that destroying the suprachiasmatic nucleus of rats destroys their circadian rhythms. The suprachiasmatic nucleus receives neural input from the eyes — that’s why these lesions were first made (by Irv Zucker, a Berkeley colleague of mine).

Lots of people think Vitamin D improves sleep. That’s not new. Here’s what one of them said, in a post promisingly titled “When is the best time to take your Vitamin D supplement?“:

In an effort to boost absorption of vitamin D, individuals were asked to take their vitamin D supplements with the largest meal of the day. After 2-3 months, vitamin D levels were checked again.At the end of the study period, vitamin D levels had risen to an average of 47.2 ng/ml (118 nmol/l) – an average increase in vitamin D levels of about 57 per cent. . . It seems sensible, I think, for individuals who are currently supplementing with vitamin D to take this with their largest evening meal.

 

Can Vitamin D Replace Sunlight? A Stunning Discovery

Wednesday, November 2nd, 2011

Primal Girl is a stay-at-home mom. I met her at the Ancestral Health Symposium. Her sleep was bad. I made recommendations. One of them was to get an hour of sunlight soon after you wake up. She can’t do that — too busy being a mom. So she decided to take Vitamin D early in the morning. After all, sunlight exposure produces Vitamin D. Here’s what happened:

One day as I was taking my supplements, I was thinking about how many units of Vitamin D your skin produces in 30 minutes of sun (20,000 I believe). I looked aghast at the 10,000 units of Vitamin D I was taking. It was 7 o’clock at night! I was essentially giving my body 15 minutes worth of bright sunlight energy. No wonder I was waking up in the middle of the night! I was telling my body that it wasn’t really time for bed, it was still the middle of the day. I wondered what would happen if I only took my Vitamin D first thing in the morning. It wouldn’t be an hour naked in the sun, but 15 minutes is better than nothing. That night I slept like shit. Worse than normal.

I usually took my supplements mid-afternoon. I vowed to take them first thing every morning. If I forgot, I would not take the Vitamin D at all that day. I tried it the next day and that night I slept like a rock. And the next night. And the next. Days I forgot and skipped the D3, I still slept great. That was the only change I made to my lifestyle and my sleep issues completely resolved. [emphasis added]

OMG! Double OMG! Like Primal Girl, I have never heard anything like this. Even I am stunned that such a simple safe easy change could have such a positive effect. (Taking Vitamin D at sunrise is a lot easier than standing on one leg four times!) I’ve read lots about circadian rhythms. Many studies showed that a drug would be much more powerful at certain times of day. Most of these studies were with rats. It never occurred to me that the time you take a vitamin could matter so much.

Strong Light and Cancer

Sunday, October 10th, 2010

From an excellent article about light pollution (not online) by David Owen in the 20 Aug 2007 issue of The New Yorker:

Richard Stevens, a cancer epidemiologists at the University of Connecticut Health Center, in Farmington, has suggested a link between cancer and the “circadian disruption” of hormones caused by artificial lighting. Early in his career, Stevens was one of many researchers struck by the markedly high incidence of breast cancer among women in the industrial world, in comparison with those in developing countries, and he at first supported the most common early hypothesis, which was that the cause must be dietary. Yet repeated studies found no clear link to food. In the early eighties, Stevens told me recently, “I literally woke up in the middle of the night — there was a street lamp outside the window, and it was so bright that I could almost read in my bedroom — and I thought, Could it be that? A few years later, he persuaded the [directors] of the Nurses’ Health Study . . . to add questions about nighttime employment, and the study subsequently revealed a strong association between working the night shift and an increased risk of breast cancer. [The researchers] wrote, “We hypothesize that the potential primary culprit for this observed association is the lack of melatonin, a cancer-protective agent whose production is severely diminished in people exposed to light at night.”

Exposure to strong light at night reduces the amplitude of your circadian rhythms. That causes a thousand changes. To decide that one of them (“lack of melatonin”) is the one that matters is highly premature. If reducing circadian amplitude increases cancer, it follows that getting more light during the day — which surely increases circadian amplitude — will reduce cancer.

The article also says:

Growing numbers of us pass most of our waking hours “in a box, looking at a box,” as Dave Crawford put it . . . Fewer and fewer of us spend much time outside at all, except in automobiles.

I have measured the light inside cars (front seats) several times and found it is quite strong (you are close to a big window). If the article is arguing that night light is bad and causes cancer, I am unconvinced. Night light exposure and daylight exposure are confounded — people who work night shifts get more night light and less daylight.
The Nurses Study paper: E Schernhammer, K Schulmeister. Light at night and cancer risk. Photochemistry and Photobiology, 2004, Vol 79, Iss 4, pp 316-318.

Genes Or Environment . . . Or Environment?

Tuesday, July 14th, 2009

Forty or fifty years ago, psychologists and other scientists talked about “genes” determining this or that. (James Watson still talks this way.) A certain percentage of the variation of this or that (e.g., intelligence) was attributed to “genes”. Hardly anyone outside genetics or behavior genetics knew what this meant, but many people thought they did. In reaction to the huge misunderstanding (e.g., those who said intelligence was “80% genetic” but did not know what this meant), psychologists began to talk about gene-environment interaction. “Is the area of a rectangle determined by its height or its width?” they like to say.

But notice how fact-free this view is. A tiny number of studies have observed gene-environment interactions but they are very difficult. I think this has made it hard to realize something basic and important. Years ago, I heard a talk about squirrel circadian rhythms by Patricia DeCoursey, the scientist who introduced the concept of phase-response curves. At her talk, she showed results from about 15 squirrels. She tested each one — with an emphasis on individual results that resembles self-experimentation — to determine how much light it needed to become entrained to a 24-hour light/dark cycle. One squirrel needed much stronger light than the others.

Here was an interesting finding that another scientist might have missed. What did it mean? Because the squirrels lived under very similar conditions (e.g., identical diets), it was almost surely a genetic difference. Let’s assume it was. In nature, sunlight is plenty strong. The lab light was weaker. In nature, the genetic difference wouldn’t make an observable difference. Only under artificial conditions did it become visible. It only became visible when the artificial conditions didn’t supply enough of something important (sunlight). In other words, the newly-visible genetic difference implied there was something lacking in the artificial conditions. The genetic difference implied the environment mattered. The opposite of the usual interpretation.

I don’t know any reason to think this is an unusual case. Aaron Blaisdell told me a story that shows its relevance to human health. Aaron is unusually sensitive to sunlight. Until recently, he could only spend 5 or 10 minutes in the sun before it became unpleasant. The condition is genetic. His mother has it; her father had it. It’s called Erythropoietic Protoporphyria. It is autosomal-dominant. Scientists even know where the gene is. That’s where the understanding of most scientists stops. A genetic condition. Recently, however, Aaron drastically changed his diet with great results, as noted earlier. At the same time as the dietary changes, his sun sensitivity got much better. He can now stay in the sun for an hour or more without discomfort. This is a gene-environment interaction, of course, but of a particular sort: The genetic effect showed there was something wrong with the environment, just as it did in DeCoursey’s experiment.

Sure, there’s always genetic variation — it’s just usually hard to see. The wrong environment makes it much easier to see. It reveals a range of genotypes, all of which would be harmless in the right environment. So when you come across a “genetic disorder” such as Erythropoetic Protoporphyria, it is likely to imply an environmental problem. No one had ever told Aaron or his mother or her father that their condition suggested that environmental changes would help them.

Morning Light and Better Sleep

Friday, June 20th, 2008

Song Cato, a friend of mine in Taiwan, writes:

I was very surprised that the quality of my sleep greatly improved after I switched to waking up at 5:30 am and walking in the park soon after that. I started it about a month ago. The park is packed with people doing everything from tai chi to ballroom dancing. I used to go to bed at 1 or 2 am. and wake up between 7 and 8:30 am with a foggy head. Now sometimes I feel tired and go to sleep at 10 pm which has never happened in my life since I went to middle school.

She got the idea from me. I go outside around 7 am every morning and fall asleep between 11 pm and midnight.

More. She gets up at about 5:15 am and gets outside about 5:30. She stays outside for at least 2.5 hours, mostly in the park, where she walks, talks to vendors, shops a little, and does simple stretching exercises. Talking to vendors = very good!

Science in Action: Sunlight and Sleep (more progress)

Tuesday, July 17th, 2007

Surely we need sunlight to sleep properly. But how much? Rats can be synchronized to a 24-hour activity rhythm with a relatively small amount of light (such as one hour) every 24 hours. This is one reason for the emphasis on morning light by sleep doctors mentioned in a previous post.

I have agreed with them. For the last 10 years I have gotten one hour of sunlight-like light every morning from a bank of fluorescent lights on the handles of my treadmill. The lights shined up at me while I exercised and watched TV. This, I thought, allowed me to get a good dose of light with low variance in when and how much and to combine light-getting with exercise. I never questioned this routine.

Then came the event that led to this Sunlight and Sleep series: In the airport during a trip to New Orleans, a student told me when she sunbathes, she sleeps better. When I got home from my trip I tested her idea. Me, too: When I was outdoors a lot (in the shade), I slept better.

I took another trip (to Los Angeles). When I got back from that trip, I decided that I would adjust the timing of the treadmill light so that it interfered less with my day. I shifted it from 9:00 am to 10:00 am (original timing) to 8:00 am to 9:00 am (new timing).

To my surprise I started waking up too early, so often it could not be a coincidence. The only change I had made was timing of the light. So the treadmill light was making things worse! I stopped it entirely. My sleep improved — no more early awakening. Huh.

Here are details:

Period 1 (treadmill light 9-10 am, little sunlight): woke up early 29 days out of 99 (29%)

Period 2 (treadmill light 9-10 am, lots of sunlight): woke up early 1 day out of 25 (4%)

Period 3 (treadmill light 8-9 am, lots of sunlight): woke up early 4 days out 8 (50%)

Period 4 (no treadmill light, lots of sunlight): woke up early 0 days out of 8 (0%).

Lots of sunlight means 6-8 hours exposure to light of roughly 1000-2000 lux. Sitting in the shade or inside next to a big window is always enough. At the low end (1000 lux) my laptop screen is easy to read; at the high end (2000 lux), which I try to avoid, it becomes slightly hard to read.

Science in Action: Sunlight and Sleep (more background)

Saturday, July 7th, 2007

An early section of Wide Awake (2006), Alan Berliner’s documentary about his life-long insomnia — he can’t fall asleep until 3 or 4 am — lists common folk remedies:

BERLINER Over the years I’ve tried to cry myself to sleep, to drink myself to sleep, aroma therapy, changing mattresses, changing pillows, lavender beads, massage therapy, white noise, meditation, counting sheep, melatonin, Valerian root, acupuncture, acupressure, chamomile tea, warm milk, hypnosis even, yoga, homeopathic medicines, marijuana, lots of sex, hot baths, herbal teas, biofeedback.
SISTER Okay, nothing worked.

Conspicuously absent: sunlight. At the end of the movie, however:

DOCTOR We have to reset your [internal] clock. Since you’re such a night owl, I’d like to move your sleep cycle earlier by having you get light exposure in the morning. When you wake up, throw on some clothes and go outdoors for an hour. I really want light to get into your eyes ’cause that’s what going to move your rhythm so you can fall asleep earlier.
ANOTHER DOCTOR Light is one of the most powerful cues for your internal clock to know what time it is. You see light and it tells you: be active during the day, sleep at night.

But the treatment they settle on is sleep deprivation: “I’d like you to spend just 6.5 hours in bed,” says a doctor. “Give you less time in bed than you want. . . . 2:30 to 9:00 am would be a reasonable way to go.” “You are going to be dysfunctional,” Berliner is warned. The film ends: “Now that I know what I have to do, the question is: Can I do it?”

This is a good summary of what people believe about how to cure insomnia. Sunshine is absent from the folk remedies you are likely hear. When doctors mention it, they emphasize early-morning sunlight.

Until recently, I too thought that sunlight exposure was important in the morning, but not during the rest of the day. Every morning I exercised on a treadmill with sunlight-spectrum light shining on me for an hour; I thought that was enough. Now I am adding to that sunlight later in the day — in the afternoon, for instance — and finding that it helps.

Science in Action: Sunlight and Sleep (progress report)

Sunday, June 17th, 2007

I’ve collected even more observations supporting the idea that outdoor light improves my sleep, as discussed earlier. Now I’d like to get some idea of the dose-response function. To sleep really well do I need two hours of outside light? Four hours? Eight hours?

I’ve started to rate my sleep on a scale where 50 = average sleep (average for the months before I started spending more time outside) and 100 = best sleep imaginable (which I got after standing about 10 hours). And I’ve started to use a stopwatch to measure how long I spend outdoors. I’ve also been using a light meter to measure the strength of light in various places. When I’m outdoors it’s almost always in the shade. Today I discovered that sitting indoors next to a cafe window the incident light was just as bright as when I sit outside. Great to know because indoors I can plug in my laptop.

A 1994 book chapter from Daniel Kripke‘s lab reported a correlation (0.24) between low light exposure and “abnormal sleep.” So the connection I am now studying has been plausible for many years. The measurements I am now making are easy, but no one made them. Perhaps too many people believe that anything other than a double-blind trial with control and experimental groups is, as Peter Norvig, Google’s Director of Research, believes, a “mistake.”