A few years ago, two studies found that people with sleep apnea have a much higher rate of cancer than people without it, even controlling for several cancer-related variables. In one study, the increase in risk was five-fold. These studies raised several questions: 1. Were the associations due to chance? 2. If real, did the associations reflect cause and effect? Surely people with sleep apnea are different in several ways from people without it. 3. If the associations did reflect cause and effect, which of the many effects of sleep apnea was/were responsible?

A new study found that rats woken up frequently got more cancer. This is a correct prediction from the idea that bad sleep increases cancer, increasing the plausibility of that idea.

[The study] used mice, housed in small groups. During the day—when mice normally sleep—a quiet, motorized brush moved through half of the cages every two minutes, forcing those mice to wake up and then go back to sleep. The rest of the mice were not disturbed. After seven days in this setting, both groups of mice were injected with cells from one of two tumor types (TC-1 or 3LLC). All mice developed palpable tumors within 9 to 12 days. Four weeks after inoculation the researchers evaluated the tumors. Tumors from mice with fragmented sleep were twice as large, for both tumor types, as those from mice that had slept normally. A follow-up experiment found that when tumor cells were implanted in the thigh muscle, which should help contain growth, the tumors were much more aggressive and invaded surrounding tissues in mice with disrupted sleep.

Great Sleep! Reduced Cancer! is a whole book (98 pp) about the connection between sleep and cancer.

Epidemiologists haven’t yet figured out that they should always measure sleep quality, just as they always measure cigarette smoking and body weight, but at least interest is growing. Both short and long sleep are associated with a higher risk of heart disease.

 

 

Philip Seymour Hoffman, the great actor, was found dead a few days ago with a needle in his arm. Last year, Cory Montieth, the actor, died in similar circumstances. Why did they die? It was hardly the first time they’d taken heroin.

Starting in the 1970s, Shepard Siegel, a psychology professor at McMaster University, did a series of rat experiments that showed that drug tolerance and craving involved a large amount of Pavlovian conditioning. Repeated exposure (e.g., injection) of Drug X in Situation Y (e.g., your bedroom at 11 p.m.) will cause learning of an association between X and Y. This association has two effects. First, when exposed to Y, you will crave X. Second, when you take Drug X in Situation Y, the effect of the drug is diminished. You become “tolerant” to it.

You have probably experienced both effects — they occur with caffeine, chocolate and alcohol, for example — but are unaware of Siegel’s explanation: Situation-drug associations. After you learn the association, Siegel said, the situation generates a response in your body that opposes (reduces) the drug effect. If the drug makes you less sensitive to pain, the conditioned response is more pain sensitivity. If the drug makes you awake, the conditioned response makes you sleepy. It’s easy to realize that drug craving involves associative learning: You notice that you crave coffee or whatever in familiar situations but not unfamiliar ones. You crave Drug X at college but not at home. It’s much harder to grasp that the tolerance involves associative learning.

Drug users, such as Hoffman and Montieth, as they become “tolerant”, take larger and larger doses, not realizing that their “tolerance” depends on a learned association. The situation becomes more and more dangerous because if you take the drug without eliciting the conditioned compensatory response, you may die. Without the conditioned response, a drug amount you survived yesterday may kill you today.

Siegel explored the possibility that this actually happened — that drug addicts died of “drug overdose” because they took the drug under unusual circumstances that didn’t evoke the compensatory response. He found plenty of support for this idea. One sort of support was interviews with “overdose” survivors. They often described unfamiliar circumstances at the time of the injection — e.g., there’s usually music, but this time there wasn’t. Another sort of support was a rat experiment with heroin. After developing tolerance to heroin, rats injected with a really large dose in a strange situation were much more likely to die than rats injected with the same dose in the same situation where they became tolerant.

I am pretty sure Hoffman and Montieth didn’t know about this research. There is a connection with the Shangri-La Diet. In both cases, Pavlovian learning has a big effect on something we care a lot about (life/death in the drug case, body weight in the diet case) and this connection is highly non-obvious.

A 2009 study followed about 9000 men for 10-20 years. It found that strength (how much you can bench and leg press) measured at the start of the study was associated with likelihood of dying of cancer during the study. Men in the upper two-thirds of the study population in strength had 40% less cancer mortality. This might be the most surprising result:

Further adjustment for BMI, percent body fat, waist circumference, or cardiorespiratory fitness had little effect on the association. The associations of BMI, percent body fat, or waist circumference with cancer mortality did not persist after further adjusting for muscular strength.

In other words, muscle strength was a better predictor than several similar measures (BMI, etc.) and these other measures stopped predicting when corrected for muscle strength. Muscle strength is closely connected to something important.

Men who are stronger by and large exercise more, no doubt. Yet muscle strength is determined by resistance training, not aerobic exercise — and it is aerobic exercise (and to some extent walking) that have been promoted by countless experts since the 1960s and the invention of the concept aerobic. Jogging reduces how much time you have for resistance training.

These findings interest me because I do a lot of resistance training — stand on one leg to exhaustion several times per day — purely to sleep better. By improving something easy to measure (sleep), these data suggest I have also been improving something hard to measure (chance of dying from cancer). Not surprising, but reassuring.

My data also suggest two different possible reasons for the strength-cancer association. One is that men who exercise more sleep better as a result; better sleep, better immune function, less cancer. Another possibility is that strength is a marker for good sleep. Among men who do equal amounts of exercise, those who sleep better will be stronger.

From The Breviary.

I am one of the presenters — that is, interviewees — at PaleoCon, which began a few days ago. The presenters were interviewed by John Durant. Among the presenters are Paul Jaminet and Chris Kresser.

In a review of biographies of Charles Dickens I found this:

In 1849 he showed a short account of his early years to his close friend John Forster, revealing a story he never told his own family: the shame-inducing months he spent, while his father was in a debtor’s prison, as a 12-year-old “laboring hind” in a factory that bottled shoe-blacking.

Suddenly I understood why he wrote Oliver Twist and why it is so good. Budding writers are told write what you know. They should be told write what you feel bad about.

The work of James Pennebaker has shown the benefits of even small amounts of self-disclosure. No doubt this is why all sorts of psychotherapy, supposedly based on enormously different theories, help roughly the same amount: All involve self-disclosure. I see this effect as something built into us by evolution to increase self-disclosure. Talking about bad experiences helps your listeners avoid what happened to you. To motivate such disclosures, evolution has built into us something that causes us to feel better after we talk this way.

Scientists are not told study what you know and they are especially not told study what you feel bad about. Scientists are mostly men, of course, and that sort of thing makes men uncomfortable. My personal science, however, suggests the correctness of this idea.