Cold and flu season has a way of turning sleep into a household problem.
One person gets sick, another person starts coughing two days later, a child wakes up overnight with a fever, and suddenly everyone in the house is operating on interrupted sleep at exactly the moment their bodies could use more recovery.
That timing is especially frustrating because sleep plays a meaningful role in immune function. Research suggests that people who regularly sleep too little are more susceptible to respiratory infections, while inadequate sleep can alter several parts of the immune response.
Sleep cannot prevent every cold or flu. Exposure matters, vaccination matters, hand hygiene matters, ventilation matters, and sometimes a virus simply makes its way through a household despite everyone doing reasonable things.
Still, sleep is one of the few factors that affects both how prepared the immune system is before exposure and how well the body can function once illness arrives.
That makes protecting sleep particularly valuable during cold and flu season.
Does Lack of Sleep Make You More Likely to Get Sick?
Researchers have tested this question in a surprisingly direct way.
In a 2015 study published in Sleep, researchers objectively tracked the sleep of 164 healthy adults for seven days. The participants were then quarantined and intentionally exposed to a rhinovirus, one of the viruses that causes the common cold.
The people who had averaged less than five hours of sleep per night were about 4.5 times as likely to develop a clinical cold as those who had averaged more than seven hours. People sleeping between five and six hours also had substantially greater odds of getting sick. [1]
An earlier study used a similar viral-challenge design with 153 adults. Researchers tracked sleep for two weeks before exposing participants to rhinovirus. People averaging less than seven hours of sleep were about 2.9 times as likely to develop a cold as people averaging eight hours or more. Poor sleep efficiency was associated with an even larger increase in susceptibility. [2]
These experiments are particularly useful because the researchers controlled the viral exposure.
In normal life, somebody who sleeps five hours might also have more stress, work longer hours, eat differently, commute more, or simply encounter more sick people. A viral-challenge study removes some of those uncertainties because everyone is deliberately exposed under controlled conditions.
The result does not mean that seven hours creates an invisible shield against viruses. It does suggest that the sleep you accumulate before exposure can influence how successfully your body handles that exposure.
Why Sleep and the Immune System Are So Closely Connected
The immune system is constantly identifying threats, coordinating inflammatory responses, producing signaling molecules, building immune memory, and destroying infected or abnormal cells.
Sleep is deeply involved in regulating those processes.
One area researchers have studied is natural killer cell activity. Natural killer cells are immune cells that help identify and destroy virus-infected cells and other abnormal cells.
In one laboratory experiment, researchers allowed healthy men to sleep normally except for four hours of sleep deprivation between 3 a.m. and 7 a.m. After that single disrupted night, average natural killer cell activity was significantly lower than baseline. Following a subsequent night of normal sleep, activity returned to baseline levels. [3]
Other studies have found complex and sometimes different immune responses depending on the timing and severity of sleep deprivation, so it would be too simplistic to say every bad night simply "turns off" natural killer cells.
The larger body of research is more convincing than any one immune marker. Sleep loss alters immune signaling, inflammatory processes, cellular immune activity, and the body's response to infectious challenges.
This is why repeated short sleep becomes particularly relevant.
An occasional terrible night happens to everyone. Cold and flu season becomes harder when five or six hours starts becoming the normal schedule for weeks.
The Toughest Part for Families
There is an unfortunate feedback loop when illness enters a household.
A sick child often sleeps poorly. Their parents then sleep poorly because they are responding to coughing, congestion, fevers, medication schedules, or simply a miserable child who wants someone nearby.
The next day, the parent is now operating on reduced sleep while also being repeatedly exposed to the same virus.
Then another family member gets sick and the cycle starts again.
The controlled cold studies give some biological credibility to what parents have experienced forever. Sleep loss during a period of heavy viral exposure is a particularly bad combination.
You cannot always fix the exposure side of the equation, especially with children in school or daycare. You can sometimes prevent everyone in the household from losing an entire night of sleep simultaneously.
For couples, that might mean dividing overnight responsibilities into shifts rather than having both adults wake up for every interruption. It could mean protecting one parent's uninterrupted block early in the night and switching later. The exact arrangement will depend on feeding, work schedules, and the child, but preserving consolidated sleep where possible is usually more useful than having two exhausted adults awake together.
The goal during these stretches is rarely perfect sleep. It is limiting how much unnecessary sleep loss gets added to an already difficult situation.
Sleep May Matter Around Vaccination Too
Cold and flu season is also vaccination season for many households, and there is evidence that sleep around vaccination may influence the immune response.
A 2023 meta-analysis combined studies examining sleep duration and antibody responses to vaccination. When sleep was measured objectively, sleeping less than six hours was associated with a substantially lower antibody response. The researchers concluded that getting adequate sleep in the days surrounding vaccination may help support the body's immune response, although they also called for larger studies to better understand timing and differences between men and women. [4]
Influenza-specific research points in a similar direction.
One study followed healthy young adults around an influenza vaccination and found that shorter sleep, particularly during the two nights before vaccination, predicted lower antibody levels to one influenza strain one and four months later. [5]
The evidence does not mean a bad night before a flu shot makes the vaccine ineffective. Vaccine response depends on many factors, and vaccination remains far more important than optimizing sleep around the appointment.
There is still a useful practical takeaway. If you are planning a vaccination, it makes sense to give yourself a reasonable sleep opportunity in the days around it rather than scheduling it in the middle of an avoidable stretch of severe sleep deprivation.
What Happens to Sleep Once You Are Already Sick?
Illness itself can disrupt sleep.
Congestion makes breathing uncomfortable. Coughing causes awakenings. Fever changes temperature regulation. Muscle aches make normal sleep positions uncomfortable. Some respiratory viruses also alter inflammatory signals that influence fatigue and sleepiness.
That explains the strange combination many people experience when sick: you can feel exhausted all day and then have a surprisingly fragmented night.
More time in bed does not always translate into uninterrupted sleep.
This is where the sleep environment becomes especially important. When the body is already dealing with an infection, reducing unnecessary sources of discomfort can improve the opportunity for restorative sleep.
A cool-mist humidifier may help relieve congestion, according to Mayo Clinic, although the evidence for improving cold symptoms is limited and the humidifier needs to be cleaned properly to prevent bacteria and mold growth. Staying hydrated and using saline nasal sprays or drops can also help with congestion. [6]
For adults who find congestion worse when lying completely flat, modest elevation of the head and upper body can also feel more comfortable. The goal is to make breathing and drainage easier without creating an awkward neck position that causes a different problem by morning.
Cold Medicine Can Make You Sleepy Without Solving the Sleep Problem
Nighttime cold medications are useful for many people because symptoms are often what keep them awake.
NyQuil Cold & Flu, for example, contains acetaminophen for pain and fever, dextromethorphan as a cough suppressant, and doxylamine, a sedating first-generation antihistamine. Its current label explicitly warns that marked drowsiness may occur. [7]
That sedation can be helpful when coughing, aches, or congestion would otherwise keep someone awake, but feeling sedated should not be confused with fixing the underlying sleep disruption created by illness.
It is also worth remembering that combination cold medications can contain ingredients that people may already be taking separately. NyQuil contains acetaminophen, for example, so adding another acetaminophen-containing product without checking the labels can lead to taking more than intended.
Follow the product directions, avoid combining products casually, and ask a pharmacist or healthcare professional when you are uncertain.
Current NyQuil labeling recommends medical evaluation if fever worsens or lasts more than three days, or if pain or cough worsens or lasts more than seven days. Similar OTC ibuprofen labeling says to contact a clinician if fever worsens or persists beyond three days. [7][8]
Those warnings are useful guardrails during a season when it is very easy to keep taking medication and assuming another day will fix everything.
Should You Work Out When You Are Sick?
This is where athletes and regular exercisers often struggle.
A workout is concrete. It is on the schedule. Missing it feels like losing momentum, especially when training has become part of your identity.
Recovery is harder to see.
A commonly used rule from sports medicine is the "neck check." Mayo Clinic says mild or moderate activity is generally reasonable when symptoms remain above the neck, including a runny nose, nasal congestion, sneezing, or a minor sore throat, provided there is no fever. Intensity and duration should usually be reduced.
Chest congestion, a hacking cough, widespread muscle aches, significant fatigue, stomach symptoms, or fever are reasons to rest rather than push through a normal workout. [9]
A few days away from hard training is extremely unlikely to erase meaningful fitness.
Trying to force a hard workout through fever or systemic illness can turn a small interruption into a longer one.
Cold and flu season is therefore a useful time to redefine what consistency means. Sometimes consistency means completing the planned workout. Sometimes it means taking the recovery day that allows you to return to the plan sooner.
How to Protect Sleep During Cold and Flu Season
There is no single sleep hack that keeps respiratory viruses out of the house, but several habits can reduce the amount of avoidable sleep disruption that gets layered on top of illness:
- Protect a regular sleep window before anyone is sick, with enough time in bed to consistently reach the amount of sleep your body needs.
- When children are waking repeatedly, divide overnight responsibilities where possible so at least one adult gets a consolidated block of sleep.
- Take a short daytime nap when nighttime sleep has been severely disrupted, especially when the alternative is simply pushing through exhaustion.
- Keep the bedroom cool, dark, quiet, and comfortable, while using a properly maintained cool-mist humidifier if congestion makes dry air uncomfortable.
- Stay hydrated and address symptoms that are repeatedly waking you rather than expecting exhaustion alone to carry you through the night.
- Reduce or skip hard training when systemic symptoms, significant fatigue, chest symptoms, or fever are present.
- Pay attention to persistent fever, worsening symptoms, breathing difficulty, dehydration, or an illness that is not following the expected course, and seek medical care when appropriate.
Most of those recommendations are fairly boring.
That is probably a feature.
When the whole household is sick, complicated optimization tends to disappear quickly. The useful habits are the ones you can still execute when everyone is tired.
Why Sleep Often Deserves Priority Over the Workout
Exercise is enormously valuable for long-term health, and regular physical activity also supports sleep and immune health.
During acute illness, the calculation changes.
A missed run can be rescheduled. A strength workout can wait several days. Fitness declines much more slowly than people often fear.
Sleep is harder to replace once a night is gone.
That becomes especially important if the previous night was already fragmented by a sick child, coughing, or fever. Adding an early alarm for a workout may take an already inadequate five-hour night and turn it into four.
The workout may feel productive because you can measure it. The extra hour of sleep is quieter, but during illness it may be the more valuable recovery decision.
This does not require abandoning training every time someone sniffles. It requires being honest about the condition your body is in that morning.
Sleep Quality Matters When Quantity Is Out of Your Control
One of the frustrating parts of cold and flu season is that sometimes there simply is no opportunity for eight uninterrupted hours.
A child is awake. You are coughing. Someone needs medicine. The baby is up again.
That is where sleep quality becomes particularly valuable.
You may not control how many interruptions happen, but you can reduce some of the other ones. A comfortable pillow can help with positioning. Cooling can help when temperature swings make the bed uncomfortable. A dark room helps make it easier to return to sleep after an awakening. Reducing noise and unnecessary screen exposure makes the sleep window you have a little easier to use.
At Lagoon, this is one reason we spend so much time thinking about the physical sleep environment.
A pillow cannot prevent influenza, cure a cold, or replace medical care.
It can help make the sleep you are able to get more comfortable and better supported, and that matters most during the periods when sleep is already hard to come by.
The Takeaway for Cold & Flu Season
Cold and flu season exposes an uncomfortable relationship between sleep and immunity.
The nights when your household is getting hit hardest are often the nights when sleep becomes hardest to protect. Meanwhile, controlled viral-challenge studies suggest that habitual short sleep can substantially increase susceptibility to the common cold, and a growing body of research connects adequate sleep with healthier immune and vaccine responses.
You cannot sleep your way out of every virus.
You can go into the season with a better-rested body, protect sleep more aggressively when illness enters the house, and give recovery priority when your body is already asking for it.
That may mean skipping a workout, splitting the night with your partner, taking the nap, going to bed earlier, or making the bedroom as comfortable as possible when congestion and fever are doing their best to ruin it.
During cold and flu season, good sleep is one of the simplest pieces of the recovery plan that is still largely under your control.
Sources
- Prather AA, Janicki-Deverts D, Hall MH, Cohen S. Behaviorally Assessed Sleep and Susceptibility to the Common Cold. Sleep. 2015;38(9):1353-1359. PubMed
- Cohen S, Doyle WJ, Alper CM, Janicki-Deverts D, Turner RB. Sleep Habits and Susceptibility to the Common Cold. Archives of Internal Medicine. 2009;169(1):62-67. PubMed
- Irwin M, Mascovich A, Gillin JC, et al. Partial Sleep Deprivation Reduces Natural Killer Cell Activity in Humans. Psychosomatic Medicine. 1994;56(6):493-498. PubMed
- Spiegel K, Rey AE, Cheylus A, et al. A Meta-Analysis of the Associations Between Insufficient Sleep Duration and Antibody Response to Vaccination. Current Biology. 2023;33(5):998-1005.e2. PubMed
- Prather AA, Hall M, Fury JM, et al. Temporal Links Between Self-Reported Sleep and Antibody Responses to the Influenza Vaccine. International Journal of Behavioral Medicine. 2021. PubMed
- Mayo Clinic. Cold Remedies: What Works, What Doesn’t, What Can’t Hurt. Mayo Clinic
- Mayo Clinic. Exercise and Illness: Work Out With a Cold? Mayo Clinic
- DailyMed. Vicks NyQuil Cold and Flu: Acetaminophen, Dextromethorphan Hydrobromide, and Doxylamine Succinate. DailyMed
- DailyMed. Ibuprofen OTC Drug Label. DailyMed
