Updated and contextualized version of an article originally published on February 1, 2021
The article retains its original focus by presenting it through a scholarly and accessible perspective, supported by verifiable references.
Authors
- Dr. A. Conte – Biologist
- Roberto Panzironi –Independent researcher
Note editoriali
- First publication: February 1, 2021
- Last update: April 18, 2026
- Version: 2026 narrative revision
Initial note for the reader: this article was published in the past and has been updated according to criteria of scientific accuracy and communicative clarity. It is for informational purposes only and does not replace medical advice. For health problems, always consult a healthcare professional.
IN BRIEF
- Short sleep (<7 hours) or fragmented sleep is associated with a higher risk of developing symptomatic respiratory infections after exposure to respiratory viruses.
- Sleep deprivation alters immune parameters (cytokines, NK cell activity, circulating microRNAs) consistent with reduced defense and an increased inflammatory state.
- Sleeping regularly and practicing good sleep hygiene can improve vaccine response and contribute to a better prognosis during infection, but the evidence is predominantly observational or short-term experimental.
- Shift workers or those with altered circadian rhythms show epidemiological signs of a higher incidence of respiratory infections: the biological mechanisms are plausible but not fully defined.
Abstract: what does science say?
Sleep is a biological process that interacts closely with the immune system. Experimental and epidemiological evidence indicates that reductions in sleep duration and its fragmentation are associated with changes in immune cell activity, cytokine profiles, and molecular markers (microRNA) that are consistent with a reduced defense capacity and increased inflammation. Experimental studies with controlled rhinovirus exposure and comparisons of groups with and without sleep after vaccination show clinical differences and antibody responses. Chronodisregulation (e.g., night work) is also associated with an increased incidence of respiratory syndromes. However, many results come from observational studies or short-term experiments: the generalizability and estimation of the long-term effect require further research. The overall picture supports the biological plausibility that adequate sleep contributes to maintaining effective immune defenses and improving the response to preventive interventions such as vaccination.
Main Section
What we mean by "insufficient sleep" and why it matters
"Insufficient sleep" generally refers to a habitual duration of less than 7 hours per night for adults, or sleep characterized by low efficiency (spending a lot of time in bed without sleeping) or frequent nocturnal awakenings. Many guidelines recommend 7–9 hours for healthy adults; the thresholds used in research often place the "risk threshold" below 7 hours. The distinction between duration (total hours) and quality (continuity, depth, efficiency) is important because immunological effects can depend on both the quantity and structure of sleep: for example, the deep sleep phase (slow waves) is linked to hormonal processes and the modulation of cytokines that influence the immune response.
What studies on infections and sleep show
In a controlled experimental study, subjects who slept less than 7 hours on average in the two weeks preceding exposure to a rhinovirus were more likely to develop a clinical cold than those who slept ≥8 hours. This suggests an association between short sleep and vulnerability to symptomatic respiratory infections [1]. Other population studies and cohorts of shift workers describe an increase in respiratory syndromes among night shift workers, although the measurement of exposure and confounding factors (patient exposure, stress, behaviors) complicate the interpretation [5].
Plausible biological mechanisms
The proposed mechanisms are multiple and consistent: regular sleep promotes the release of hormones (e.g., GH, prolactin) that support immune function and modulates the secretion of pro- and anti-inflammatory cytokines; acute or chronic deprivation alters the count and activity of cellular subpopulations such as natural killer (NK) cells and T lymphocytes, and modifies circulating molecular profiles, including microRNAs associated with inflammation and vascular health [2][6][3]. These biological alterations constitute a plausible basis for the increased susceptibility to infections observed in some studies.
PRACTICAL SECTION
What it means in practice
For the general public, evidence indicates that maintaining regular sleep habits and prioritizing adequate nightly duration are reasonable behaviors to support immune function. Experimental and cohort data show that sleep around the time of vaccination can improve antibody response and that nocturnal deprivation can reduce it [4][7]. In at-risk occupational settings (shift work), managing sleep and work exposures is relevant for collective health, although specific recommendations must be personalized. In any case, this information is not intended to prescribe therapies: for persistent sleep disorders, it is advisable to consult a doctor or a specialized center. Professor Luigi Ferini Strambi (Vita-Salute San Raffaele University; director of the Sleep Medicine Center at IRCCS San Raffaele Turro Hospital) emphasizes the importance of preparing for sleep with relaxing routines and limiting exposure to electronic devices before bed, habits that promote regularity and quality of rest.
Useful and non-prescriptive indications
To reduce the risk of insufficient sleep and its possible effects: maintain regular sleep/wake times; optimize the nighttime environment (dark, quiet, comfortable temperature); limit evening use of bright screens; avoid caffeine in the late hours; if working shifts, use specific organizational and medical strategies. These measures have practical bases and reduce the probability of chronic sleep deprivation, but they do not replace clinical advice in cases of insomnia or sleep disorders.
KEY POINTS TO REMEMBER
- Habitual sleep reduction (<7 hours) is associated with a higher probability of illness after exposure to respiratory viruses in experimental studies. [1]
- Sleep deprivation alters detectable immune parameters (e.g., NK activity, cytokine profile, microRNA), consistent with reduced defense and increased inflammation. [2][6][3]
- Sleep close to the time of vaccination can influence antibody response; the evidence is supported by experimental studies and a recent meta-analysis. [4][7]
- Shift work and the resulting chronodisregulation are associated with an increased number of respiratory episodes in prospective cohorts, but the picture remains complex. [5]
- Practical sleep hygiene recommendations are sensible for the general population; for clinical problems, consult a specialist.
Limitations of Evidence
The available evidence is robust in describing associations and plausible mechanisms, but it has significant limitations: much of the data is observational and cannot establish a definite causal relationship; short-term experiments show significant biological effects, but their generalizability to real-life chronic deprivation models is partial. Some experimental studies (e.g., rhinovirus challenge) provide strong indications of an association between short sleep and illness, but limited samples and controlled settings differ from the variability of broader populations. Furthermore, objective sleep measurement (polysomnography, actigraphy) is not always present in large studies, which often rely on self-assessment. Finally, confounding factors (stress, behaviors, occupational exposure) can modulate the observed relationships. For all these reasons, a cautious interpretation is necessary: the associations are credible and biologically supported, but the causal strength and the magnitude of the long-term effect require additional research.
Editorial conclusion
The current body of knowledge paints a coherent picture: sleep is not a secondary factor with respect to immune health, but an element integrated with the regulation of defensive responses and the modulation of inflammation. Experimental evidence, biological mechanisms, and population studies converge towards the plausibility that adequate and regular sleep contributes to reducing vulnerability to infections and improving the response to preventive interventions such as vaccination. However, the complexity of contexts (shift work, comorbidities, age) and methodological limitations require caution in practical conclusions. For the citizen, adopting healthy sleep habits is a reasonable strategy for general health; for the healthcare professional, integrating sleep assessment into prevention and care can offer additional benefits documented by the literature.
Editorial note
This article has been updated to align with recent peer-reviewed literature and to meet criteria for clarity, transparency, and verifiability. Scientific claims are supported by references with verified DOIs; the information provided is for informational purposes only and does not replace individual medical advice.
SCIENTIFIC RESEARCH
- Cohen S, Doyle WJ, Alper CM, Janicki‑Deverts D, Turner RB. Sleep habits and susceptibility to the common cold. Arch Intern Med. 2009;169(1):62–67. https://doi.org/10.1001/archinternmed.2008.505
- Irwin M, McClintick J, Costlow C, et al. Partial night sleep deprivation reduces natural killer and cellular immune responses in humans. FASEB J. 1996;10(5):643–653. https://doi.org/10.1096/fasebj.10.5.8621064
- Besedovsky L, Lange T, Haack M. The sleep‑immune crosstalk in health and disease. Physiol Rev. 2019;99(3):1325–1380. https://doi.org/10.1152/physrev.00010.2018
- Meta‑analysis: A meta‑analysis of the associations between insufficient sleep duration and antibody response to vaccination. Current Biology. 2023;33(5):998–1005.e2. https://doi.org/10.1016/j.cub.2023.02.017
- Loef B, van Baarle D, van der Beek AJ, Sanders EAM, Bruijning‑Verhagen P, Proper KI. Shift work and respiratory infections in health‑care workers (Klokwerk+ Study). Am J Epidemiol. 2019;188(3):509–517. https://doi.org/10.1093/aje/kwy258
- Hijmans JG, Levy M, Garcia V, et al. Insufficient sleep is associated with a pro‑atherogenic circulating microRNA signature. Exp Physiol. 2019;104(6):975–982. https://doi.org/10.1113/EP087469
- Lange T, Perras B, Fehm HL, Born J. Sleep enhances the human antibody response to hepatitis A vaccination. Psychosom Med. 2003;65(5):831–835. https://doi.org/10.1097/01.psy.0000091382.61178.f1
- Zhang L, Li T, Chen L, et al. Association of sleep quality before and after SARS‑CoV‑2 infection with clinical outcomes in hospitalized patients with COVID‑19 in China. EXCLI J. 2021;20:894–906. https://doi.org/10.17179/excli2021-3451
[If some requested references or data are not present in the original, the text uses clearly identified placeholders in square brackets.]