Researchers who set out to study fatigue on a Navy warship found out firsthand that getting good rest while underway is not easy.
Rachel Markwald, a sleep physiologist with the Naval Health Research Center, and her team spent two weeks aboard the amphibious assault ship Essex. They led a study Markwald said could someday help commanders spot when crew members are reaching dangerous fatigue levels that might interfere with their duties.
About 250 sailors and 50 Marines volunteered to participate in the CREW -- or Crew Readiness, Endurance and Watchstanding -- study. They each wore two smart devices -- a bracelet and a ring -- that tracked sleep patterns, heart and breathing rates, body temperature changes and more.
"Sleep can be challenging in an environment that runs 24 hours a day, seven days a week," Markwald said. "Understanding if a department is approaching more dangerous levels of fatigue as a group could provide an opportunity to mitigate [risk]."
The new study is being done in collaboration with Naval Surface Force U.S. Pacific Fleet, Markwald said. Crew fatigue was found to be a factor in a pair of fatal 2017 Navy ship collisions in the Pacific.
Studies on sleep and the military have since found that active-duty troops are twice as likely as civilians to suffer from sleep deprivation. Insomnia and obstructive sleep apnea diagnoses have also spiked in the military community, both of which can cause short- and long-term health problems.
The CREW study leverages new smart device technologies that monitor changes that can point to fatigue and even health problems. The researchers also are interested in seeing whether body temperature and other factors can catch asymptomatic or pre-symptomatic illnesses.
The CREW study seeks to identify those changes "before they become potentially problematic," Markwald said.
Researchers want to triple the size of the CREW study by collecting data from 1,000 Navy and Marine volunteers. Other vessels will be selected where volunteers will be given the chance to wear the smart devices at sea to participate in the study.
Sailors and Marines on the Essex wore the Oura Ring and the Fatigue Science ReadiBand. The devices use an accelerometer and other sensors to read activity, rest cycles, body temperature and other data.
Since the Oura Ring can measure cardiorespiratory metrics, such as respiratory rate, the Navy wants to study whether it also can also catch asymptomatic or pre-symptomatic illnesses. Some Navy ships that experienced COVID-19 outbreaks during the global coronavirus pandemic saw hundreds of asymptomatic cases that made the illness difficult to catch.
Sailors and Marines wearing the devices were able to access their health data daily while underway. The study team also spoke with participants about the data, Markwald said, and provided education and mentorship about what the numbers meant to those who wanted it. Participants were interested in learning about their sleep patterns, she said, and how to make improvements.
Leaders could see only aggregated, non-identifiable data from the study. The goal isn't to track people, Markwald said, but to give leaders a glimpse at the crews' health and fatigue status.
"We hope to be able to provide that on a day-to-day basis," she said. "We want to understand, 'What does the ship look like relative to another ship in terms of sleep and fatigue levels?' or 'What are they looking like in the engineering department?'"
Markwald said she's grateful to the sailors and Marines willing to participate in the study, along with the ship's leadership and medical team. She said being on the Essex gave her a new appreciation for the fatigue challenges troops face when at sea, where noise and temperature fluctuations can constantly interrupt their sleep, and is hopeful the study leads people to be better informed on the importance sleep plays in job performance.
"I can say I've never slept in a berthing compartment with a couple hundred other folks before," she said. "I think that's always good as a research team to be able to understand more intimately the problem set."