We’re approaching periscope depth. The lights in the control room have been shut off. This is done for the benefit of the man at the periscope, who will shortly be taking a look around in the 5:00 a.m. darkness at the surface. To everyone else up here, many of whom are going on four or fewer hours of sleep, darkness is the opposite of helpful. Not only is it warm and dark in here, but because we’re nearing the surface, the submarine is now rocking gently with the swells. “Torture,” says the helmsman.
Torture was the word used by sleep researcher William Dement, who, as a student in the 1950s, helped Nathaniel Kleitman document Rapid Eye Movement (REM) sleep. Before there were eyelid electrodes and electrooculargraphs, there were grad students pulling all-nighters. “Staring at the closed eyes of human adults by the dim light of a 30-watt bulb in the middle of the night was sheer torture,” Dement wrote in a tribute to Kleitman, who is known in his field as “the Father of Sleep Research.” (Tougher yet was the job of the chaperone Kleitman insisted be present when the subject was female: watching someone else watching the eyes of a sleeping human all night.)
THE PHOTOGRAPH dates from 1938. Nathaniel Kleitman sits at a dinner table, knife and fork crossed in a slab of hickory-smoked ham. What’s unusual about this ham supper is that it took place in a cave 119 feet underground. Kleitman, with a graduate student assisting, spent thirty-two days in Kentucky’s Mammoth Cave investigating the cycles of human sleep and wakefulness. He wished to find out: to what extent are these rhythms tied to external cues and routines? If you took away the cues—sunlight, established mealtimes, regular business hours—could people slip easily into an altered routine? Going underground seemed like the easiest[59] path to an answer.
Submarines interested Kleitman, because, like caves, they present a sort of real-world laboratory for chronobiology. Kleitman, in turn, interested the Submarine Force. They were, as they are today, having some alertness issues. Kleitman came up with a watch schedule that took advantage of a submarine’s isolation from sunlight—the fact that it’s always, as Murray put it, “70 degrees and fluorescent.” It should thus be possible, Kleitman reasoned, to put each of three separate watch crews on a different schedule by staggering their waking hour, each crew beginning the day at a different time.
Beginning in 1949, three submarines, the Corsair, the Toro, and the Tusk, gave the Kleitman watchbill a two-week trial. At the end of it, Kleitman distributed questionnaires. “Should new schedule replace old?” read the last question. “Yes,” said 19 sailors. “No,” said 143. What happened? Catastrophic decompensation in the galley. Rather than cooking and cleaning up one breakfast, one lunch, and one dinner every twenty-four hours, galley crew had to do three of each, accommodating the different start times of each watch group’s “day.” The cooks were exhausted and peeved. The galley was a mess—“never clear and clean for more than an hour and a half,” causing every meal to be “flavored with the odor of the last, and the whole permeated with the aura of aged refuse.” And because a submarine’s galley doubles as its rec room, movies could no longer be screened. “Recreational activities had to be curtailed to such an extent that they degenerated to periods of loafing around trying to keep out of the way.” Friends who weren’t assigned to the same “time zone” were now isolated from each other. “It is considered neither desirable nor feasible to continue this experimental watch schedule any further,” concluded the final memo in the submarine folders of the Nathaniel Kleitman Papers.
There were some in the Submarine Force who believed Kleitman’s watchbill deserved a fuller chance, that the galley and recreation routines could have been adjusted. One executive officer blamed “just plain orneriness. Sailors,” he wrote, “hate to try anything new.” It is perhaps no coincidence that the colloquialisms “don’t rock the boat” and “don’t make waves” share a nautical element.
The officer was probably right. The Kleitman watchbill was grounded in sound science. Sunlight is our most powerful internal clock-setter. Along with rods and cones, we have a third kind of photoreceptor, one that is keyed to the blue wavelengths of sunlight. Information about this light, or the lack of it, is passed along to the pineal gland, producer of melatonin, the body’s natural soporific. Sunlight triggers a cutoff of melatonin, bringing on wakefulness. (Indoor light—particularly the light from tablets and smartphones—can also suppress melatonin, but nowhere near as dramatically as sunlight.) This is why night shift workers who drive home in the morning through sunlight and then struggle to fall asleep may find relief by buying amber-lensed Bono-style glasses that block the sun’s blue light wavelengths.
NSMRL has been developing goggles rimmed with battery-powered lights that emit the blue melatonin-suppressing wavelengths, thereby fooling the brain into thinking it’s daytime. Depending on which direction you’re flying, one or another of these distinctive eyewear options can help you preadjust to a new time zone. Or, in the case of Special Operations types heading to the Middle East to undertake secret 3:00 a.m. missions, not adjust. Lieutenant Kate Couturier, a circadian rhythm researcher at NSMRL, outfitted a planeload of Navy SEALs with blue light–emitting goggles on a series of flights from Guam to the East Coast of the United States, to see if it were possible to make them unattractive to females, oops, I mean, to keep them on Guam time. It worked.
It is probably fair to say that circadian dysrhythmia affects alertness and performance as much as or more than the amount of sleep a person has been getting. In the late 1990s, a team of sleep researchers and statisticians from Stanford University analyzed twenty-five seasons of Monday Night Football scores. Because the games were played at 9:00 p.m. eastern standard time, West Coast players were essentially competing at 6:00 p.m.—a time chronobiologically closer to the body’s late afternoon peak for physical performance.[60] As the researchers predicted, West Coast teams were shown to have won more often and by more points per game. The effect was striking enough that teams sometimes travel a few days in advance of a game to give the players’ body rhythms a chance to adjust.
Another complicating factor with military sleep is that the people making the schedules are often middle-aged and the people following them are teenagers. Not only do adolescents typically need more sleep, but their circadian rhythm is “phase-delayed” compared to adults’; melatonin production begins later in the evening, with the result that a teenager or even a twenty-two-year-old may not feel sleepy until well past midnight. Horrifically, the traditional boot camp lights-out is at 10:00 p.m., with a 4:00 a.m. wake-up.
Jeff Dyche told me about an admiral who approached him wanting to address sleep deprivation in the Navy boot camps. She wanted to move lights-out to an hour earlier—9:00 p.m.—to give the lads more time to sleep. Dyche quietly took her for a walk around camp after lights-out. “Almost every sailor was sitting up wide awake, twiddling his thumbs. They’re all going to sleep at midnight no matter how early they have to get up.” Dyche managed to move some 4:00 a.m. wake-ups to 6:00 a.m. Test scores improved so dramatically that one of the command master chiefs assumed there’d been a cheating scandal.
For the past four decades, submarines have run on a watchbill known as “sixes,” which divides sailors’ time into six-hour chunks: six hours on watch, six for other duties and studies, six for personal time and sleep, then back on watch. The creation of an 18-hour day saw each sailor putting in six extra hours of watch time every 24-hour period. The problem is that his activities ceased to align with his biological rhythms. He’s now working when his body badly wants to be sleeping. “It’s like flying to Paris every day,” Kate Couturier said. Without Paris. “It’s a quadruple whammy,” said Couturier’s colleague Jerry Lamb, when I met with him and other Navy sleep experts before boarding the Tennessee. “We flip around their sleeping and working times, we work them like dogs, we give them very short periods of sleep, and we wake them up for drills.” He turned to his colleagues. “Did I miss anything?”
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Though not, as correspondence in the Nathaniel Kleitman Papers reveals, without its challenges. To avoid “the danger of rats jumping up,” the researchers’ beds were outfitted with special five-foot-high legs with “tin rat guards.” Alas, there was no rat guard for publicity-seeking tourist attraction managers and noisome reporters. Kleitman had made clear he wanted no press involvement, but about a week into the experiment, Mammoth Cave general manager W. W. Thompson sent a note down with the evening meal saying that reporters had
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It’s not just alertness that waxes and wanes. Gut motility also follows a circadian pattern. Healthy humans rarely crap after midnight, unless they’ve just arrived in a distant time zone.