NU504 Assignment 6: Impact of Sleep Deprivation on Cold Susceptibility

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Purdue University Globle 

NU504 Scientific and Analytic Approaches to Advanced Evidence-Based Practice

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Date

How Sleep Deprivation Increases the Risk of the Common Cold: 

Getting enough sleep is one of the most effective ways to strengthen the immune system and lower the risk of developing the common cold. Research consistently shows that adults who sleep fewer than seven hours each night are more likely to experience upper respiratory infections than those who regularly achieve the recommended 7–9 hours of quality sleep. Sleep supports the production of immune cells, regulates inflammatory responses, and enhances the body’s ability to fight viruses, making it an essential component of disease prevention and overall health.

Sleep is far more than a period of rest. It is a complex biological process that restores physical and mental function while supporting critical immune activities. During sleep, the body repairs damaged tissues, balances hormone levels, consolidates memory, and produces proteins that help defend against infections. When sleep is consistently shortened or disrupted, these protective processes become less effective, increasing susceptibility to viral illnesses and slowing recovery after infection.

NU504 Assignment 6: Impact of Sleep Deprivation on Cold Susceptibility

Modern lifestyles have contributed to widespread sleep deprivation. Long working hours, shift schedules, chronic stress, excessive screen time, and irregular sleep routines often prevent adults from obtaining sufficient rest. As sleep deficiency becomes more common, healthcare professionals are increasingly recognizing its role as a modifiable risk factor for respiratory infections and chronic disease.

Evidence from randomized clinical trials, prospective cohort studies, and systematic reviews demonstrates a strong relationship between inadequate sleep and impaired immune function. Although a small number of studies have reported mixed findings, the overall evidence supports healthy sleep as an evidence-based strategy for reducing the risk of the common cold and promoting long-term wellness.

Why Sleep Is Essential for Immune Health

Sleep and immune function are closely interconnected. During healthy sleep, the immune system produces cytokines—specialized proteins that regulate inflammation and coordinate the body’s defense against viruses, bacteria, and other pathogens. Certain cytokines increase during periods of infection, injury, or stress, enabling immune cells to respond efficiently and support recovery.

Insufficient sleep disrupts these protective mechanisms. Chronic sleep deprivation reduces cytokine production, lowers antibody responses, and decreases the activity of infection-fighting immune cells. As a result, the body becomes less capable of resisting viral infections and may require more time to recover after illness.

Research also indicates that poor sleep contributes to chronic low-grade inflammation, which is associated with numerous long-term health conditions in addition to weakened immunity. This relationship highlights why sleep quality is considered a fundamental component of preventive healthcare and evidence-based nursing practice.

Adults experiencing ongoing sleep deprivation may face:

• Reduced immune response

• Greater susceptibility to viral infections

• Slower recovery from illness

• Increased inflammation

• Persistent physical and mental fatigue

• Higher risk of chronic diseases, including cardiovascular disease and diabetes

These physiological effects explain why healthcare providers routinely recommend healthy sleep habits as part of comprehensive wellness and disease prevention strategies.

Current evidence indicates that adults who consistently sleep fewer than seven hours per night have a significantly greater likelihood of developing upper respiratory infections than individuals who regularly obtain seven to nine hours of sleep.

Refined PICOT Question

The PICOT framework provides a structured approach for developing focused clinical questions that guide evidence-based practice and research. By defining the population, intervention or exposure, comparison, outcome, and timeframe, clinicians can identify relevant evidence more efficiently.

For this evidence review, the refined PICOT question is presented below.

Population (P)

Adults.

Intervention/Exposure (I)

Sleeping fewer than five hours per night.

Comparison (C)

Adults who regularly sleep seven or more hours each night.

Outcome (O)

Development of the common cold or another upper respiratory infection.

Time (T)

During the winter months, specifically November through February.

The resulting clinical question is:

Among adults, does sleeping fewer than five hours per night, compared with sleeping seven or more hours, increase the likelihood of developing the common cold during the winter months?

This question focuses on determining whether inadequate sleep is an independent risk factor for respiratory infections and whether improving sleep duration could serve as a practical preventive intervention.

The PICOT framework enables clinicians to identify high-quality evidence that supports informed clinical decisions regarding sleep and immune health.

Literature Search Strategy

A comprehensive literature search was conducted to identify high-quality research examining the relationship between sleep deprivation and susceptibility to respiratory infections. Multiple evidence-based healthcare databases were searched to ensure that the review included current, peer-reviewed, and clinically relevant studies.

The primary databases included:

• PubMed

• Cochrane Library

• Academic nursing databases

• MEDLINE

• EMBASE

The following search terms and combinations were used to identify relevant literature:

• Sleep deprivation

• Sleep duration

• Sleep quality

• Sleep hygiene

• Sleep and immunity

• Immune function

• Common cold

• Upper respiratory infection

To improve the quality and reliability of the evidence, the search was limited to:

• Peer-reviewed publications

• Full-text articles

• Human studies

• English-language publications

• Recent evidence whenever available

The initial search identified thousands of potentially relevant publications. After removing duplicate records and excluding studies that did not specifically examine sleep duration or respiratory infections, four high-quality studies were selected for detailed analysis. These studies represented the strongest available evidence investigating the association between sleep deprivation and susceptibility to the common cold.

A structured and transparent search strategy improves the credibility of evidence reviews by reducing selection bias and ensuring that clinical recommendations are based on the best available research.

Evidence Review: Sleep Disturbance After Hospitalization and Critical Illness

One of the most comprehensive reviews examining the health consequences of disrupted sleep was conducted by Altman and colleagues (2017). This systematic review evaluated how sleep quality changes following hospitalization, particularly after intensive care treatment and critical illness, while also exploring the broader effects of sleep disruption on recovery and immune function.

Researchers searched several major medical databases, including PubMed, MEDLINE, and EMBASE. More than 2,000 publications were initially identified. After applying predefined eligibility criteria, 22 studies met the inclusion requirements for detailed analysis.

The review included:

• Twenty-one prospective cohort studies

• One cross-sectional study

Researchers evaluated sleep using validated assessment methods, including standardized questionnaires, polysomnography, and actigraphy. These tools allowed investigators to assess both subjective sleep experiences and objective sleep measurements.

The findings demonstrated that sleep disturbances remained common long after hospital discharge.

Reported prevalence included:

• 50–66.7% within one month after discharge

• 34–64.3% between one and three months

• 22–57% between three and six months

• 10–61% beyond six months

These findings indicate that sleep disruption frequently persists for months following severe illness, potentially delaying physical recovery and immune restoration.

The review also emphasized several important physiological benefits of healthy sleep, including:

• Improved immune regulation

• Enhanced memory consolidation

• Balanced neuroendocrine function

• Reduced inflammatory responses

• Faster recovery from illness

Conversely, chronic sleep disruption was associated with increased risks of:

• Cardiovascular disease

• Depression

• Cognitive impairment

• Reduced immune function

• Increased mortality

Although the review focused primarily on patients recovering from hospitalization rather than healthy adults, its findings reinforce the essential role of restorative sleep in immune recovery and long-term health.

Persistent sleep disturbances following hospitalization may impair immune recovery, prolong rehabilitation, and increase the risk of long-term health complications.

Critical Appraisal and Error Analysis

Critical appraisal is an essential component of evidence-based practice because it evaluates the quality, validity, and applicability of research before findings are incorporated into clinical decision-making.

The systematic review by Altman et al. demonstrated several methodological strengths. Researchers applied clear inclusion and exclusion criteria, helping improve the overall quality of the evidence.

Studies involving the following populations were excluded:

• Burn injuries

• Neurosurgical patients

• Postsurgical recovery

• Non-English publications

• Case reports

• Narrative reviews

• Expert opinion articles

These exclusions reduced potential sources of bias and improved consistency across the included studies.

Despite these strengths, several limitations should be considered.

First, investigators used different methods to assess sleep quality. Some studies relied on self-reported questionnaires, whereas others used objective monitoring tools such as polysomnography and actigraphy. This methodological variation made direct comparisons more challenging.

Second, the included studies differed substantially in participant characteristics, follow-up duration, and measurement techniques, contributing to clinical heterogeneity.

Finally, relatively small sample sizes across several studies prevented researchers from performing a formal meta-analysis, limiting the ability to generate pooled estimates.

Despite these limitations, the systematic review provides strong evidence supporting the importance of healthy sleep for immune recovery and overall health. The findings also reinforce the need for healthcare providers to recognize sleep as a critical component of patient recovery and preventive care.

Quantitative Study: Sleep Duration and Upper Respiratory Infections in Military Recruits

One of the strongest quantitative studies examining the relationship between sleep deprivation and respiratory infections was conducted by Wentz et al. (2018). The researchers investigated whether inadequate sleep increased the likelihood of upper respiratory infections (URIs) among British Army recruits during basic military training. Military training provides a valuable research setting because participants often experience intense physical exertion, psychological stress, and reduced sleep, all of which can influence immune function.

The study included 651 healthy military recruits with an average age of approximately 22 years. Participants completed questionnaires before and after training to report their usual sleep duration. Researchers also collected demographic and lifestyle information to account for factors that could influence infection risk.

The study considered several potential confounding variables, including:

• Smoking status

• Alcohol consumption

• Body mass index (BMI)

• Seasonal recruitment period

• Sex

Medical records were reviewed throughout the training period to identify physician-diagnosed upper respiratory infections, providing objective clinical outcomes rather than relying solely on participant self-reports.

The results demonstrated a significant decline in sleep duration during military training. Before training, only 13% of recruits reported sleeping fewer than seven hours per night. During training, this proportion increased to approximately 38%, highlighting how demanding environments can contribute to sleep deprivation.

After adjusting for confounding variables, recruits sleeping less than six hours per night were approximately four times more likely to develop upper respiratory infections than those who consistently obtained the recommended 7–9 hours of sleep.

These findings provide strong evidence that inadequate sleep substantially increases vulnerability to respiratory illnesses, particularly during periods of prolonged physical and psychological stress.

The study offers several methodological strengths:

• Large sample size

• Standardized physician-confirmed diagnoses

• Adjustment for important lifestyle and health variables

• Prospective study design

However, because the participants were young military recruits rather than members of the general population, the findings may not be fully generalizable to older adults or individuals with chronic medical conditions.

Current evidence suggests that adults consistently sleeping fewer than six hours each night may have a substantially higher risk of developing upper respiratory infections than individuals who regularly obtain sufficient sleep.

Sleep Habits and Susceptibility to the Common Cold

Among the most influential investigations examining sleep and immune function is the experimental study conducted by Cohen et al. (2009). Unlike observational studies, this research directly evaluated whether sleep duration affected an individual’s susceptibility to the common cold after controlled exposure to a rhinovirus.

The study enrolled 153 healthy adults between 21 and 55 years of age. Participants had no significant underlying medical conditions, allowing researchers to better isolate the effects of sleep on immune function.

Before viral exposure, participants’ sleep patterns were monitored for 14 consecutive days using validated instruments adapted from the Pittsburgh Sleep Quality Index (PSQI) and the Pittsburgh Sleep Diary.

Researchers evaluated several sleep-related measures, including:

• Average nightly sleep duration

• Sleep efficiency

• Time spent awake during the night

• Subjective feelings of restfulness

After the observation period, participants received nasal drops containing a rhinovirus under carefully controlled laboratory conditions. They were then quarantined and monitored for five days while researchers assessed the development of clinical illness.

Clinical outcomes included:

• Nasal congestion

• Runny nose

• Sneezing

• Sore throat

• Cough

• Mucus production

• Viral antibody response

• Nasal mucociliary clearance

The findings revealed a strong relationship between inadequate sleep and infection risk. Participants sleeping fewer than seven hours per night were nearly three times more likely to develop a clinically confirmed common cold than individuals sleeping eight hours or more.

Researchers also discovered that sleep efficiency was an important predictor of immune resistance. Individuals who spent less time actually sleeping while in bed were significantly more susceptible to infection, even if they believed they had rested adequately.

Interestingly, subjective perceptions of feeling rested were not significant predictors of illness. Instead, objective measures of sleep duration and efficiency more accurately reflected immune resilience.

These findings demonstrate that obtaining adequate sleep is more important than simply feeling rested. Healthy sleep duration and efficient sleep appear to strengthen the body’s natural defenses against viral infections.

Controlled experimental research consistently indicates that insufficient sleep significantly increases susceptibility to the common cold following viral exposure.

Swedish Cohort Study: Sleep, Physical Activity, and Respiratory Infections

To further investigate the relationship between sleep and respiratory illness, Ghilotti et al. (2018) conducted a large prospective cohort study involving 2,038 employed adults between 25 and 64 years of age. This was the largest population-based study included in the evidence review.

Participants completed comprehensive questionnaires assessing multiple lifestyle and health factors, including:

• Sleep duration

• Sleep quality

• Physical activity

• Occupational environment

• Lifestyle behaviors

• Family structure

• Overall health status

Researchers classified sleep duration into three categories:

• Short sleep: Five hours or less

• Normal sleep: Six to seven hours

• Long sleep: Eight hours or more

Participants were followed for nine months, covering the peak respiratory virus season from September through May.

Whenever participants developed symptoms suggestive of respiratory infection, they completed an online symptom questionnaire. Researchers also collected nasal swabs that were analyzed using polymerase chain reaction (PCR) testing to identify respiratory viruses.

Unlike the previous studies, this investigation did not identify a statistically significant association between sleep duration, sleep quality, physical activity, and laboratory-confirmed respiratory infections.

Although these findings appear inconsistent with much of the existing literature, several methodological differences may explain the discrepancy. Variations in participant characteristics, viral exposure, environmental conditions, and outcome measurements can influence study results.

Despite reporting different conclusions, the study possessed several strengths:

• Large sample size

• Prospective design

• Random participant selection

• Laboratory confirmation of viral infections

• Comprehensive assessment of lifestyle variables

The study illustrates that scientific evidence occasionally produces mixed findings. Such differences do not necessarily invalidate previous research but instead highlight the complexity of immune function and the influence of multiple biological, environmental, and behavioral factors.

Although some cohort studies report no significant association, the overall body of evidence continues to support the importance of adequate sleep for maintaining healthy immune function.

Evidence Summary

The evidence reviewed demonstrates a consistent pattern indicating that sleep plays a critical role in immune health and resistance to respiratory infections.

Among the four major studies evaluated:

• Three studies found that inadequate sleep significantly increased susceptibility to respiratory infections.

• One large cohort study reported no statistically significant association between sleep duration and upper respiratory infections.

• Controlled experimental research provided the strongest evidence linking short sleep duration to increased risk of the common cold.

• Multiple investigations identified both sleep duration and sleep efficiency as important predictors of immune performance.

Collectively, these findings indicate that chronic sleep deprivation weakens immune defenses and increases vulnerability to viral infections. Although individual studies may differ because of variations in research design, participant populations, and methods of measuring illness, the overall evidence strongly supports healthy sleep as an important preventive health strategy.

Current evidence indicates that adults who regularly obtain seven to nine hours of quality sleep are generally less likely to develop respiratory infections than individuals experiencing chronic sleep deprivation.

Application to Nursing Practice

The evidence reviewed highlights the importance of incorporating sleep promotion into routine healthcare and disease prevention. Nurses and advanced practice providers are uniquely positioned to educate patients about the relationship between sleep, immune function, and overall health.

One of the most effective interventions is sleep hygiene education, which encourages behaviors and environmental modifications that promote restorative sleep.

Healthcare professionals should encourage patients to:

• Maintain a consistent sleep and wake schedule.

• Aim for 7–9 hours of sleep each night.

• Limit caffeine and nicotine several hours before bedtime.

• Reduce exposure to electronic screens before sleeping.

• Create a quiet, dark, and comfortable sleep environment.

• Engage in regular daytime physical activity.

• Avoid heavy meals and alcohol close to bedtime.

• Practice stress-management and relaxation techniques.

Hospitalized patients require special attention because frequent interruptions, medical procedures, lighting, and environmental noise often disrupt normal sleep patterns. Coordinating nursing care to reduce unnecessary nighttime disturbances may improve recovery and support immune function.

Routine sleep assessments should also become part of preventive health evaluations, particularly for individuals with:

• Recurrent respiratory infections

• Diabetes

• Cardiovascular disease

• Obesity

• Chronic stress

• Mental health disorders

• Shift-work schedules

Because sleep is a modifiable health behavior, patient education regarding healthy sleep habits represents a practical, low-cost intervention that may improve both short-term recovery and long-term health outcomes.

Evaluation of the Evidence

The evidence reviewed demonstrates a strong relationship between sleep duration and immune health. Although individual studies differ in their methodologies and participant populations, the majority conclude that insufficient sleep increases susceptibility to viral respiratory infections, including the common cold.

Among the four primary studies evaluated:

• Three studies found a significant association between inadequate sleep and an increased risk of respiratory infections.

• One prospective cohort study did not identify a statistically significant relationship between sleep duration and respiratory illness.

• The strongest evidence came from the controlled experimental study by Cohen et al. (2009), which directly measured participants’ susceptibility to the common cold after rhinovirus exposure.

• Multiple studies identified both sleep duration and sleep efficiency as key predictors of immune function.

Overall, the findings indicate that chronic sleep deprivation weakens the body’s natural defenses against infection. While differences in study design, participant characteristics, and outcome measures may explain occasional inconsistencies, the collective evidence supports healthy sleep as an essential component of disease prevention and evidence-based healthcare.

Current research consistently suggests that adults who regularly obtain 7–9 hours of quality sleep are less likely to develop respiratory infections than individuals who experience chronic sleep deprivation.

Validity of the Evidence

The reviewed studies demonstrate strong internal validity because they employed established research methodologies, standardized measurement tools, and objective clinical outcomes.

Several factors strengthen the credibility of the evidence:

• Use of validated sleep assessment instruments, including the Pittsburgh Sleep Quality Index (PSQI), polysomnography, and actigraphy.

• Inclusion of physician-confirmed or laboratory-confirmed respiratory infections rather than relying solely on self-reported illness.

• Prospective cohort and experimental study designs that reduce recall bias.

• Adjustment for important confounding variables such as age, smoking status, alcohol consumption, body mass index, and seasonal variation.

The systematic review by Altman et al. (2017) also followed rigorous inclusion and exclusion criteria, ensuring that only relevant, high-quality studies were included.

Despite these strengths, some limitations remain. Differences in sleep assessment methods, follow-up periods, participant demographics, and sample sizes limited direct comparisons across studies. In addition, the heterogeneity of the available research prevented formal meta-analysis in some cases.

Nevertheless, the overall quality of the evidence is sufficient to support clinical recommendations promoting healthy sleep as part of preventive healthcare.

Reliability of the Evidence

Reliability refers to the consistency of findings across multiple independent studies.

Despite variations in research settings and populations, the majority of investigations reported similar conclusions regarding the relationship between inadequate sleep and increased infection risk.

Consistent findings include:

• Sleeping fewer than seven hours is associated with reduced immune function.

• Poor sleep efficiency contributes to greater susceptibility to viral infections.

• Chronic sleep deprivation delays immune recovery and prolongs illness.

• Healthy sleep habits support immune regulation and overall health.

Although one cohort study reported conflicting results, the broader body of evidence demonstrates a consistent pattern supporting the importance of sufficient sleep for immune resilience.

Repeated findings across experimental, observational, and systematic review studies increase confidence in the reliability of these conclusions.

Applicability to Clinical Practice

The reviewed evidence is broadly applicable to many healthcare settings because it includes diverse participant populations, including healthy adults, military personnel, hospitalized patients, and community-dwelling adults.

These findings have important implications for evidence-based nursing practice and preventive medicine.

Healthcare professionals should routinely assess sleep habits during patient evaluations and provide education regarding the health benefits of adequate sleep.

Sleep promotion is particularly relevant for individuals who have:

• Frequent respiratory infections

• Chronic stress

• Diabetes

• Cardiovascular disease

• Obesity

• Depression or anxiety

• Shift-work schedules

• Compromised immune function

Incorporating sleep assessments into routine clinical practice allows healthcare providers to identify patients at increased risk for immune dysfunction and implement early interventions.

Because improving sleep habits is inexpensive, non-invasive, and supported by high-quality evidence, it represents an effective strategy for enhancing patient outcomes and reducing preventable illness.

Research supports integrating sleep hygiene education into routine preventive care to strengthen immune function and promote long-term health.

Conclusion

Current evidence indicates that adequate sleep is one of the most important lifestyle factors supporting a healthy immune system and reducing susceptibility to the common cold and other upper respiratory infections. Adults who consistently sleep fewer than seven hours each night are generally at greater risk of viral illness than those who regularly obtain the recommended seven to nine hours of quality sleep.

Sleep influences numerous physiological processes that are essential for immune defense, including cytokine production, antibody formation, inflammatory regulation, and tissue repair. Chronic sleep deprivation disrupts these mechanisms, reducing the body’s ability to fight infection and recover efficiently from illness.

Although one large cohort study did not identify a statistically significant relationship between sleep duration and respiratory infections, the majority of high-quality evidence—including systematic reviews, prospective cohort studies, and controlled experimental research—supports a meaningful association between insufficient sleep and increased infection risk.

For healthcare professionals, particularly nurses and advanced practice providers, sleep assessment should be considered an essential component of comprehensive patient care. Educating patients about healthy sleep habits offers a practical, evidence-based intervention that can improve immune function, support recovery, and reduce the burden of preventable respiratory illnesses.

Ultimately, sleep should be recognized not simply as a period of rest but as a vital biological process that promotes immune resilience, enhances overall health, and contributes to long-term disease prevention.

Sleep is a modifiable health behavior, and prioritizing consistent, high-quality sleep represents one of the simplest and most effective strategies for protecting immune health.

Frequently Asked Questions

Does sleeping fewer than seven hours increase the risk of getting a cold?

Yes. Multiple clinical studies have found that adults who consistently sleep fewer than seven hours each night are more likely to develop upper respiratory infections, including the common cold. Adequate sleep supports immune function and improves the body’s ability to resist viral infections.

Why does sleep affect the immune system?

During sleep, the immune system produces cytokines, antibodies, and specialized immune cells that help fight infections and regulate inflammation. Chronic sleep deprivation reduces these protective responses, making it more difficult for the body to defend itself against viruses.

How much sleep do healthy adults need?

Most healthy adults should aim for 7–9 hours of quality sleep each night. This recommendation is supported by sleep medicine experts and public health organizations to maintain optimal physical health, cognitive performance, and immune function.

Can improving sleep reduce the likelihood of illness?

Improving sleep habits can strengthen immune function and may reduce the risk of respiratory infections. While adequate sleep cannot prevent every illness, it is an important component of a healthy lifestyle and supports faster recovery when illness occurs.

What are the best sleep hygiene practices?

Effective sleep hygiene includes:

• Maintaining a consistent sleep schedule.

• Limiting caffeine, nicotine, and alcohol before bedtime.

• Reducing screen time in the evening.

• Creating a cool, quiet, and dark sleep environment.

• Exercising regularly during the day.

• Practicing relaxation techniques to manage stress.

• Avoiding heavy meals immediately before bedtime.

Healthy sleep habits improve both sleep quality and overall immune resilience.

Research consistently demonstrates that obtaining sufficient, high-quality sleep strengthens immune function and may reduce susceptibility to common respiratory infections.

Clinical evidence indicates that adults who sleep fewer than seven hours each night have a significantly greater likelihood of developing the common cold than individuals who consistently obtain the recommended amount of sleep.

Sleep hygiene education is a practical, low-cost, evidence-based intervention that healthcare professionals can use to promote wellness, strengthen immune health, and improve patient outcomes.

References

Altman, M. T., Knauert, M. P., & Pisani, M. A. (2017). Sleep disturbance after hospitalization and critical illness: A systematic review. Annals of the American Thoracic Society, 14(9), 1457–1468. https://doi.org/10.1513/AnnalsATS.201702-148SR

Asif, N., Iqbal, R., & Nazir, C. F. (2017). Human immune system during sleep. American Journal of Clinical and Experimental Immunology, 6(6), 92–96. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5806561/

Cohen, S., Doyle, W. J., Alper, C. M., Janicki-Deverts, D., & Turner, R. B. (2009). Sleep habits and susceptibility to the common cold. Archives of Internal Medicine, 169(1), 62–67. https://doi.org/10.1001/archinternmed.2008.505

Ghilotti, F., Pesonen, A. S., Raposo, S. E., Winell, H., Nyrén, O., Trolle Lagerros, Y., & Plymoth, A. (2018). Physical activity, sleep and risk of respiratory infections: A Swedish cohort study. PLoS ONE, 13(1), e0190270. https://doi.org/10.1371/journal.pone.0190270

NU504 Assignment 6: Impact of Sleep Deprivation on Cold Susceptibility

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Wentz, L. M., Ward, M. D., Potter, C., Oliver, S. J., Jackson, S., Izard, R. M., Greeves, J. P., & Walsh, N. P. (2018). Increased risk of upper respiratory infection in military recruits who report sleeping less than 6 h per night. Military Medicine, 183(11–12), e699–e704. https://doi.org/10.1093/milmed/usy090