On dead worms and the need for sleep

The C. elegans worm, which is used to study the microbiology of sleep. Image from sas.upenn.edu (via Samy Belfer’s research)

Imagine if bouncing back from an all-nighter could kill you. Such was the case, by analogy, for a group of roundworms recently studied by a team of researchers at Penn’s Perelman School of Medicine.

The full paper can be found here, but the main idea involved modeling sleep deprivation in the C. elegans worm. Researchers stimulated (i.e., poked) the worms awake during what would normally be a lethargic period. For control worms, this “deprivation” provoked a homeostatic sleep response — bodily adjustments to compel the worm to rest, like feelings of exhaustion in humans that are coordinated by the brain. For worms with a mutation blocking these adjustments, their response at first looked better than normal. They stayed awake through what was meant to be a rest period and seemed to avoid their equivalent of exhaustion. Except then, a bunch of them died.

You might say, hmm, that’s interesting enough — but this obviously wasn’t an “all-nighter” in a human sense of the phrase. These worms don’t even experience what we humans think of as being sleep. Yet as Penn’s chief sleep researcher, David Dinges, explained, simple animal models have often fostered insights into the mechanisms of human sleep. “You can’t just say this is irrelevant, that it’s just a worm hanging in a bubble of water. It’s highly relevant,” Dinges said.

In particular, he pointed out that mechanisms for sleep and energy conservation are dictated by features of our natural environment — like the sunlight/darkness cycle — that affect all manner of living things, from worms to people.

Given this connection, I didn’t feel completely ridiculous responding to this study by reconsidering the way humans gauge our own need for sleep. Just to tease out this idea, let’s anthropomorphize these worms a bit by thinking of them like people. The mutants would be those irritatingly efficient individuals who seem able to stay up all night and still function in the morning. But in this case, seemingly out of nowhere, the little guys met their maker. Even if the worms looked like they could manage without rest, they clearly couldn’t.

I wonder if something like this often happens with people. We might think we’ve recovered fine from a few nights of scant sleep after we’ve had some caffeine pick-me-ups or a good nap. We subscribe to the notion of “catching up”: going days or weeks at a time on unhealthy schedules, with the assumption our bodies will recover once we hit a weekend or vacation period when we can sleep in. Though these binges are meant to compensate for sleep we’ve lost, it looks like in many ways they fall short.

This is the not so rosy pictured outlined by psychology doctoral student Andrea Spaeth, who studies sleep and energy balance under Dinges. Spaeth noted that long-term sleep loss is associated with substantial weight gain and unhealthy eating behaviors. After someone sleeps in, or “recovers,” following a stint of deprivation, they typically just return to baseline levels of eating. That means they’ll have to work extra to make up for any damage already caused to their fitness during their time of insufficient sleep.

“Catching up” may also fail to restore function. Take someone who sleeps less than seven hours a night for multiple days and then binges with a 12-hour sleep session (in other words, many a college student). Even after that binge, performance on a range of cognitive tasks is still likely to be impaired.

So though the worm findings are interesting in their own right, they can also be a reminder: we can still need sleep even when we feel fine or think we’ve “caught up.” The stakes may not be quite as high for us as they were for the tragic C. elegansĀ mutants. Still, the potential for chronic weight gain and decreased cognitive function is desirable for no one.

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