Military Recruits Who Typically Sleep <6 Hours Miss Training Due To Upper Respiratory Infection

Abstract

The National Sleep Foundation recommends 7−9 hours of sleep per night for young adults. Habitually sleeping <6 hours per night has been shown to lower immunity and increase susceptibility to common cold following exposure to rhinovirus. However, no investigations have examined the importance of sleep duration on upper respiratory infection (URTI) and loss of training days in military recruits. PURPOSE: To identify if military recruits who typically sleep <6 hours per night during training suffer a greater incidence of URTI and, as a consequence, miss more training than recruits who meet sleep recommendations. METHODS: Participants included 651 British Army recruits aged 22 ± 3 years who completed 13 weeks of Phase 1 military training (67% males, 33% females). Recruits were members of 21 platoons (11 male, 10 female) who commenced training across the seasons (19% winter, 19% spring, 28% summer, and 33% autumn). At week 13, participants completed a questionnaire asking the normal time they went to sleep and awoke during training. Incidence of physician-diagnosed URTI and reduced or missed training days due to URTI were retrieved from medical records. RESULTS: Typical sleep duration during training was reported as 7.0 ± 0.8 hours per night with 5% of recruits reporting they normally slept <6 hours and 60% of recruits reporting 7-9 hours of sleep each night. In a logistic regression model, recruits who slept <6 hours per night were 4 times more likely to be diagnosed with URTI compared with recruits who slept 7−9 hours per night after controlling for sex, BMI, alcohol, smoking, and season of recruitment (OR 4.6; 95% CI, 1.7–12.8, P < 0.01). URTI’s diagnosed in recruits who slept <6 hours were spread across both sexes, 5 platoons and 3 seasons, showing sufficient heterogeneity. Overall, 49 recruits (8%) were diagnosed with at least one URTI, and 3 recruits (<1%) were diagnosed with two URTI’s. On average, each URTI resulted in 2.9 ± 1.5 reduced or missed training days. CONCLUSION: These findings show that military recruits who sleep <6 hours per night are more susceptible to URTI and miss more training due to URTI. Future studies should examine interventions to improve sleep hygiene in military training. Supported by MoD, UK.