Caffeine consumption and sleep in a submarine environment: An observational study.

Area of Science:

• Occupational Health
• Sleep Science
• Human Performance

Background:

• Submariners face significant sleep challenges due to environmental and operational factors.
• Caffeine is commonly used by submariners to combat sleepiness, but its impact on sleep in this unique environment is not well understood.

Purpose of the Study:

• To explore the relationship between caffeine consumption and sleep quantity/quality in U.S. Navy submariners.
• To investigate objective and subjective sleep metrics alongside caffeine intake during a submarine patrol.

Main Methods:

• Collected objective sleep data (wrist actigraphy) from 45 participants.
• Gathered self-reported sleep metrics and caffeine consumption data from 58 U.S. Navy Sailors.
• Compared pre-underway and at-sea data over a 30-day submarine patrol.

Main Results:

• Caffeine consumption was lower at sea compared to pre-underway levels.
• Higher caffeine intake correlated positively with sleep efficiency and negatively with wake after sleep onset and sleep fragmentation.
• Increased caffeine consumption was also negatively associated with self-reported sleep duration at sea.

Conclusions:

• The study reveals a complex relationship between caffeine and sleep in the submarine environment.
• Findings suggest that caffeine may improve certain objective sleep parameters despite potential negative impacts on perceived sleep duration.
• Unique submarine operational demands and caffeine use patterns warrant consideration for developing effective sleep countermeasures.