Use meditation to sleep less?

Is it possible to sleep less and stay functional?

Methods I heard of...

Most people use caffeine (coffee, tea, caffeine pills, energy drinks) to stay awake in sleep deprived state, but dependence develops so they eventually need more and there is caffeine withdraw symptoms. Modafinil does similar thing without development of physical dependence, but long-term health effect is unknown; you also get a tiny risk of developing nasty rash. Then there is the hexaphasic sleep pattern that entails 90 minutes of sleep in 24 hours. Not something I want to mess with. Finally, raw foodists often report less sleeping needs, but I don't find raw foodism nutritionally appealing. Enough nonsense. Today I want to focus on meditation.

Meditation reduces sleep need? Evidence:

The following figure summarizes a study done in Kentucky 2010. This is one of my favorite papers, and it is one of the things that get me into meditation:

In this study, wakefulness is estimated by "PVT test" which measures reaction times. The subjects, 10 healthy university students, have no prior experience on meditation. A week before the PVT test, they  maintain a regular sleeping schedule and avoid substances such as caffeine that would otherwise affects the result. "Treatment" refers to either control (read / talk), napping and meditation (focus on abdominal movement during breathing, kneeling position) that lasts 40 minutes. In the sleep-deprivation experiment, subjects are deprived of sleep for 32 hours (so treasure the figure above!). In the figure, data points falling below the line entails a decrease in sleep need. The rest? A figure worth a thousand words!

You may find it surprising that napping actually increases the reaction times. It does. Indeed, this is the well-established phenomena of sleep inertia. In layman terms, you still feel a little dizzy shortly after waking up!

Sleep times of experienced meditators vs non-meditators

The authors then study the sleeping times of 7 experienced meditators (>3 years) with EEG and sleep journals:

You argue, "Hey, maybe these experienced meditators are sleepy zombies". A standard "sleepiness test", the so-called MSLT test (basically measures how long it takes for the subject to fall asleep), shows that indeed, it takes them longer to fall asleep. Meaning, while we might be a sleepy zombie, they are definitely not!

Last word...

I like to cite more papers but this is the only study that shows the direct effect. If you know other references, let me know. I'd love to read it.

There are plenty of studies on monitoring brain waves of meditating subjects. But I decide to leave it later.

The sciences behind teeth brushing

Why brush teeth?

Feynman questioned the utility of tooth brushing. Is the efficacy of tooth brushing a myth? Unlikely. Fluorides in toothpaste (and drinking water) is shown to reduce solubility of enamel, enhance remineralization of enamel and interfere with enzyme activities in oral bacteria. After brushing, saliva show measurable increase in fluoride content. The dissipation of fluoride apparently depends on what you do after brushing, e.g., eating immediately reduces fluoride content in saliva by 12-15 times.

Brushing after meal? Before meal?

There is some evidence suggesting tooth brushing within 30 minutes after meal (especially a meal containing acidic food) leads to increased abrasion of enamel. The theory is that acidic food in a meal soften the enamel and make it vulnerable to mechanical wearing (i.e., brushing). Although the error bar in the aforementioned study is large, it is of our own interest to err on the safe side!

Finally, a study suggests a toothpaste 'massage' once a day superposed on regular brushing boost up fluoride concentration in saliva.

Long, horizontal brushing strokes are bad?

Various sources in internet claims that long horizontal strokes produces more abrasion than vertical ones, and even cause gum recession. However, I failed to find a first-hand, real study on this effect, and to be honest with you, it doesn't make sense to me.