Viagra for the sleep-deprived?

Epidemiologists often follow a set of criteria called the "Hill Criteria" to determine what causes a disease.  The list includes things like consistency, and strength of the cause and effect relationship -- the cause should reliably produce the effect, and the effect should increase as the cause increases.  And so on.  Unfortunately for epidemiology, there are many situations in which these criteria aren't met, even with known causes, but there is one criterion that is pretty reliable and that's the one that says that cause should come before effect.  But it's a problem when you can't tell which is the cause and which the effect.

The BBC reports that scientists have found the "clue to getting a good night's sleep."  The paper they are reporting on, from Current Biology, summarizes it this way:

Common experience suggests that [the] fragility of sleep is highly variable between people, but it is unclear what mechanisms drive these differences. Here we show that it is possible to predict an individual's ability to maintain sleep in the face of sound using spontaneous brain rhythms from electroencephalography (EEG). The sleep spindle is a thalamocortical rhythm manifested on the EEG as a brief 11–15 Hz oscillation and is thought to be capable of modulating the influence of external stimuli. Its rate of occurrence, while variable across people, is stable across nights. We found that individuals who generated more sleep spindles during a quiet night of sleep went on to exhibit higher tolerance for noise during a subsequent, noisy night of sleep. This result shows that the sleeping brain's spontaneous activity heralds individual resilience to disruptive stimuli.

So they believe they've found the brain's way to tune out noise during sleep, and it works something like this: During sleep, when the brain receives sensory input like noise or light, the thalamus interacts with the cortex, and this produces " transient fluctuations of the brain's electric field visible on the EEG as rhythmic spindles" (seen in part A of the figure). Some have proposed that these spindles are signals of the brain interfering with the transmission of sensory input to the cortex, where they are perceived -- meaning that you become consciously aware of them -- a process that isn't normally disrupted when we're awake.  If this is true, then the more spindles you make, the less likely your sleep is to be disturbed by external stimuli. 

To test the association of spindle number with sleep disruption, the researchers monitored the sleep of 12 healthy individuals for 3 nights with EEGs.  The first night was quiet, while they introduced noise at regular intervals during the 2nd and 3rd nights (regularity could be a problem here, though, as people tend to acclimate to regular sound, but oh well).  They found a statistically significant association of spindle rate with sleep stability.  They found spindle count to be consistent over 3 nights, and "suitable for predicting sleep continuity under noisy conditions", and they suspect that the biological relationship reflects "the cumulative effects of spindle and sound collision" -- that is, spindles themselves inhibit the perception of sound during sleep.  Naturally, future studies are needed, primarily of "interventions" to promote spindle production in light sleepers (i.e., drugs).

So, are these guys on to something?  Will they soon be marketing a Viagra equivalent for the sleep-deprived? 

Well, here's what a sleep researcher unrelated to this study, and quoted in the BBC story, has to say (this is a consideration not mentioned in the actual paper, so we applaud the BBC for adding it to their story).

Professor Jim Horne of the Sleep Research Centre at Loughborough University added: "Sleep spindles certainly help to block outside noise. There are other interpretations for this study, though, as those people with fewer spindles may simply be 'lighter sleepers' and more likely to wake up with the noise - hence less sleep and fewer spindles.

So, what's cause and what's effect?  That's indeed a problem.

But here's another one -- do those of us who toss and turn really need to be diagnosed with a 'condition' or even a 'disease', that demands doctors' attention and health-care funds?  And whose reframing could make some people potentially very rich?  Why do we turn every toss into a topic for 'research', and publish our handkerchief every time we blow our nose? We have a lot of other reasons to lose sleep, but not over this.