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Studies could mean end of 18-hour days on subs

Since the 1960s, submariners have typically maintained 18-hour days on deployment, creating an underwater lifestyle with daily rhythms linked to meals and artificial lighting.

But the Navy could end up changing that cycle back to 24 hours, as mounting research suggests the existing schedule can impair performance and cause health problems.

Studies show that even without clocks and sunlight, human biology is best suited for 24-hour cycles. Moving to 18-hour days can create conditions similar to jet lag, said Lt. Christopher Steele, the lead researcher for fatigue issues with the Submarine Medical Research Laboratory in Connecticut.

“It’s like flying to Paris every day,” Steele said of the 18-hour day. “Unfortunately, that results in unpredictable rhythms for alertness.”

Steele and other researchers from his laboratory plan to go on a long-term deployment later this year to study submariners’ response to various sleeping patterns.

Senior Navy leaders will not make any decisions until the study is complete.

“There are currently no plans to change the standard 18-hour watch-standing cycle onboard U.S. Navy submarines,” said Cmdr. Patrick McNally, spokesman for the Submarine Force.

“When the study is completed we will evaluate the results, balanced with other requirements, and make a determination if any changes to watch-standing cycles are necessary.”

A submariner’s typical day at sea revolves around six hours on watch, six hours of other duties and six hours of sleep.

Previous, shorter studies aboard the ballistic-missile submarine Maryland and the attack submarine Pittsburgh during the past year suggested that dividing a 24-hour day into three eight-hour shifts resulted in better performance, Steele said.

Some more complex three-day cycles were also examined — stacking six-hour shifts, then taking larger 12- or 24-hour blocks off for sleep — were not as successful, Steele said.

Without optimal sleeping patterns, sailors can show lower levels of alertness, limited reaction times or irritability, Steele said.

Steele’s research is based on the study of circadian rhythms, the biochemical and physiological fluctuations that people experience every day.

For example, the body produces a hormone known as melatonin that typically peaks on a 24-hour cycle during deep sleep. But studies show the daily production of melatonin cannot synchronize with an 18-hour day, Steele said.

The 18-hour day also could be making it more difficult for submariners to stay in good shape, Steele said.

Chronic disruption in circadian rhythms can increase risk for heart disease, diabetes, high blood pressure and obesity, according to a study by Harvard University researchers released March 2. The study focused on civilian shift workers.

Any changes in watch schedules could come from individual submarine commanders, McNally said.

“It is also important to note that commanding officers retain the authority and flexibility to adjust watch schedules as necessary to maintain the safest and most effective watch rotation given the complex environment in which submarines operate,” he said.

3 work-cycle options

Officials with the Naval Submarine Medical Research Laboratory are studying three work-cycle options for submariners:

• 18-hour day: Six hours on watch, 12 hours off (current practice).

• 24-hour day: Eight hours on watch, 16 hours off.

• Three-day cycle: Six hours on, six off, six on, 12 off, six on, six off, six on, 24 off.