Sleep and immune function

• A. Sleep has no measurable effect on the immune system.
• B. Sleep supports immune function, and insufficient sleep is associated with weaker immune responses. ✓
• C. Sleep only affects the immune system in people over age 65.
• D. Sleep weakens the immune system to conserve energy.

Why: Research consistently shows that adequate sleep supports immune defenses, while chronic sleep loss is linked to reduced immune responses and increased susceptibility to infection.

• A. Wakefulness
• B. Slow-wave (deep) sleep ✓
• C. Rapid eye movement (REM) sleep only
• D. The moment of falling asleep

Why: Cytokine release, including proteins involved in immune signaling, is thought to be enhanced during slow-wave (non-REM deep) sleep, which is one reason deep sleep is considered important for immune health.

• A. The vaccine response is unaffected by sleep.
• B. Antibody production is often weaker than in well-rested individuals. ✓
• C. Antibody production is always stronger than in well-rested individuals.
• D. The vaccine becomes ineffective regardless of sleep.

Why: Studies have found that people who sleep poorly around the time of vaccination tend to produce lower antibody levels, suggesting sleep influences how well the immune system builds protection.

• A. Adrenaline
• B. Insulin
• C. Melatonin ✓
• D. Thyroxine

Why: Melatonin, released in the evening and during the night, has immunomodulatory effects and helps regulate inflammatory responses, linking the sleep-wake cycle to immune function.

• A. Sleep deprivation increases the number of viruses in the environment.
• B. Reduced sleep can impair immune cell activity and the body's ability to respond to pathogens. ✓
• C. Sleep deprivation causes the body to stop producing white blood cells entirely.
• D. Cold viruses only infect people who are awake at night.

Why: Chronic sleep loss can impair the activity of immune cells such as natural killer cells and T cells, reducing the body's ability to fight off pathogens like cold viruses.

• A. Stage 1 (light sleep)
• B. Stage 2 (light sleep with sleep spindles)
• C. Stage 3 (slow-wave or deep sleep) ✓
• D. REM sleep

Why: Stage 3, also called slow-wave sleep, is characterized by high-amplitude, low-frequency delta waves. It is linked to physical restoration, growth hormone release, and immune regulation, including increased cytokine activity that supports immune responses.

• A. REM sleep ✓
• B. Stage 1 sleep
• C. Stage 2 sleep
• D. Stage 3 sleep

Why: REM (rapid eye movement) sleep features brain activity similar to wakefulness, rapid eye movements, and vivid dreaming. Muscle atonia also occurs during this stage, which prevents us from acting out dreams.

• A. 1 to 2 cycles
• B. 3 to 5 cycles ✓
• C. 8 to 10 cycles
• D. 12 or more cycles

Why: A typical sleep cycle lasts about 90 to 110 minutes, and most adults complete roughly 3 to 5 cycles in a night of around 7 to 9 hours. Each cycle moves through non-REM stages and then REM sleep.

• A. Sleep has no measurable effect on the immune system
• B. Sleep only affects the immune system during illness
• C. Adequate sleep supports immune responses, such as antibody production and T-cell activity ✓
• D. Sleep suppresses all immune activity to conserve energy

Why: Research shows that sufficient sleep supports immune function, including the production of antibodies and the activity of T cells. Chronic sleep deprivation is associated with weaker responses to vaccines and a higher risk of infection.

• A. Stage 1 sleep
• B. REM sleep ✓
• C. Awake resting state
• D. Stage 2 sleep only

Why: REM sleep plays a key role in consolidating certain types of memories and processing emotional experiences. Together with deep sleep, it helps the brain organize and store information gathered during the day.

• A. The pituitary gland
• B. The suprachiasmatic nucleus in the hypothalamus ✓
• C. The pineal gland's melatonin output alone
• D. The thymus gland

Why: The suprachiasmatic nucleus (SCN) in the hypothalamus is the master circadian pacemaker. It receives light input from the retina and synchronizes peripheral clocks throughout the body, including those in immune cells and tissues.

• A. Natural killer cell activity is generally lowest in the early morning hours
• B. Natural killer cell activity is generally highest during early sleep ✓
• C. Lymphocyte numbers drop to zero until waking
• D. Immune activity is unaffected by the time of day

Why: Natural killer (NK) cell numbers and cytotoxic activity tend to rise during sleep, particularly in early nighttime hours, and decline toward the morning. This reflects circadian and sleep-related regulation of immune surveillance.

• A. Cortisol
• B. Insulin
• C. Melatonin ✓
• D. Thyroxine

Why: Melatonin is released by the pineal gland in response to darkness. Besides signaling circadian phase, it has been shown to modulate immune cell function, although its effects are complex and context-dependent.

• A. It peaks late at night and is lowest at midday
• B. It is flat throughout the day
• C. It peaks in the early morning, around the time of waking, and is lowest around midnight ✓
• D. It peaks at midday and is lowest in the early morning

Why: Cortisol shows a diurnal rhythm with a peak near waking (the cortisol awakening response) and a trough around midnight. Its anti-inflammatory effects therefore vary across the day, influencing immune timing.

• A. Vaccines have no interaction with the immune system
• B. Immune responses to vaccination can vary with the time of day, and sleep around vaccination may influence antibody production ✓
• C. Vaccines only work during daylight hours
• D. Circadian rhythms only affect viral infections, not vaccines

Why: Research suggests that the timing of vaccination relative to the circadian cycle, and sleep quality around vaccination, can influence the strength of antibody responses. This is an active area of study in immune timing and sleep research.

• A. Neutrophils
• B. Natural killer (NK) cells ✓
• C. Red blood cells
• D. Platelets

Why: Studies have shown that sleep deprivation reduces circulating natural killer (NK) cell activity and numbers. NK cells are important for early defense against viruses and tumor cells, so this reduction can weaken initial immune responses to infection.

• A. Cortisol peaks at midnight and remains high until morning
• B. Growth hormone is released mainly during deep slow-wave sleep ✓
• C. Insulin is suppressed completely during all sleep stages
• D. Adrenaline levels increase steadily through the night

Why: Growth hormone is released in large pulses during slow-wave (deep) sleep. Growth hormone interacts with immune function, and disruption of deep sleep can alter this signaling. Cortisol, by contrast, is typically lowest around midnight, not peaking then.

• A. Interleukin-1 beta (IL-1β) ✓
• B. Interleukin-10 (IL-10)
• C. Interferon-gamma (IFN-γ)
• D. Tumor necrosis factor-alpha (TNF-α) is never produced during sleep

Why: Interleukin-1 beta is a pro-inflammatory cytokine that is linked to increased slow-wave sleep, particularly during infection. This bidirectional relationship suggests that sleep helps coordinate the body's response to illness.

• A. A stronger antibody response
• B. A weaker antibody response ✓
• C. No change in antibody levels
• D. Faster elimination of the vaccine antigen

Why: Several studies, including work on influenza and hepatitis B vaccines, found that people who sleep less than about six hours in the nights around vaccination tend to produce lower antibody levels, suggesting reduced vaccine effectiveness.

• A. Chronic short sleep has no measurable effect on infection risk
• B. Chronic short sleep is associated with a higher risk of catching respiratory infections such as the common cold ✓
• C. Only people over age 70 experience increased infection risk from poor sleep
• D. Sleep loss reduces infection risk by increasing immune cell activity

Why: Controlled studies, such as Cohen and colleagues' work in 2009, found that people sleeping less than about seven hours per night were roughly three times more likely to develop a cold after exposure to a rhinovirus than those sleeping eight or more hours. Chronic sleep restriction thus raises infection risk.

• A. Insulin
• B. Interleukin-1 (IL-1) ✓
• C. Cortisol
• D. Melatonin

Why: Interleukin-1 is a pro-inflammatory cytokine that helps coordinate immune responses. Its levels tend to rise with sleep deprivation, and it also acts on the brain to promote sleepiness, which is part of why cytokines are linked to sleep regulation.

• A. Inflammation has no effect on sleep quality or duration.
• B. Inflammation tends to increase sleepiness and can disrupt sleep, while sleep helps regulate inflammatory responses. ✓
• C. Inflammation always causes insomnia with no bidirectional effects.
• D. Sleep increases inflammation in all cases to fight infection.

Why: The relationship is bidirectional. Inflammatory cytokines can promote sleep and fatigue during infection, but chronic inflammation can fragment sleep, and adequate sleep supports the balance of immune and inflammatory processes.

• A. Wakefulness
• B. Slow-wave (deep) sleep ✓
• C. Rapid eye movement (REM) sleep only
• D. Sleep onset during the first few minutes

Why: Cytokine release, including IL-1 and TNF-alpha, is associated with slow-wave sleep. This is one reason deep sleep is considered important for immune regulation and recovery.

• A. Interleukin-6 (IL-6)
• B. Tumor necrosis factor-alpha (TNF-alpha) ✓
• C. Adrenaline
• D. Serotonin

Why: TNF-alpha is a pro-inflammatory cytokine released during infection. Along with IL-1, it contributes to the sleepiness and fatigue experienced during illness, reflecting the link between immune activity and sleep.

• A. Stronger and more consistent vaccine responses
• B. Reduced immune efficiency and a higher susceptibility to infections ✓
• C. Complete elimination of inflammation
• D. No measurable change in immune function

Why: Chronic short sleep is associated with reduced immune function, including weaker responses to vaccines and greater susceptibility to infections, along with elevated markers of systemic inflammation.

• A. Sleep has no measurable effect on how the immune system responds to vaccines.
• B. Adequate sleep around the time of vaccination is associated with a stronger antibody response. ✓
• C. Sleep only affects vaccine response in people over 65 years old.
• D. Sleeping more than 10 hours after vaccination reduces antibody production.

Why: Studies have consistently linked adequate sleep before and after vaccination with higher antibody levels, suggesting that sleep supports the immune processes needed to build effective immunity.

• A. Wakefulness
• B. REM sleep only
• C. Slow-wave (deep) sleep ✓
• D. Light stage 1 sleep

Why: Slow-wave sleep is associated with the release of certain immune signaling molecules and enhanced immune memory consolidation, making it especially relevant to vaccine responses.

• A. Adrenaline
• B. Insulin
• C. Growth hormone ✓
• D. Thyroxine

Why: Growth hormone is released in large pulses during deep sleep and plays a role in regulating immune cell activity and function.

• A. A stronger and longer-lasting antibody response than well-rested individuals.
• B. No difference compared to well-rested individuals.
• C. A weaker antibody response and potentially reduced protection. ✓
• D. Immediate immunity without the need for any antibody production.

Why: Sleep deprivation is associated with reduced antibody production following vaccination, which can lead to weaker and potentially shorter-lived protection.

• A. Because sleep prevents vaccines from causing any side effects.
• B. Because sleep helps the immune system mount a more effective response to the vaccine. ✓
• C. Because vaccines must be given during sleep to work properly.
• D. Because sleep eliminates the need for booster doses.

Why: Good sleep supports the immune processes that turn vaccine exposure into lasting protection, so maintaining healthy sleep around vaccination can help optimize the response.

• A. Stage 1 light sleep
• B. Slow-wave (deep) sleep ✓
• C. REM sleep
• D. Wakefulness just before sleep onset

Why: Slow-wave (deep) sleep, the most restorative stage of non-REM sleep, is when growth hormone is released in its largest pulses. This hormone supports tissue repair and immune function, which is why getting enough deep sleep matters for immune health.

• A. 3 to 4 hours
• B. 5 to 6 hours
• C. 7 to 9 hours ✓
• D. 10 to 12 hours

Why: Major health organizations, including the American Academy of Sleep Medicine and the CDC, recommend 7 to 9 hours of sleep per night for adults. Consistently sleeping less than this has been linked to weaker immune responses, including reduced antibody production after vaccination.

• A. The antibody response is usually stronger because the body is more alert
• B. There is no measurable effect on vaccine response
• C. Antibody production is often reduced, which may make the vaccine less effective ✓
• D. The vaccine takes effect faster but wears off sooner

Why: Studies have found that people who sleep poorly around the time of vaccination tend to produce fewer antibodies than well-rested people. Sleep supports the immune system's ability to form lasting immune memory, so inadequate sleep can blunt vaccine effectiveness.

• A. Drinking alcohol before bed to fall asleep faster
• B. Keeping a consistent sleep and wake schedule, even on weekends ✓
• C. Exercising vigorously right before going to bed
• D. Sleeping in a bright room to stay on a regular rhythm

Why: A consistent sleep-wake schedule helps regulate the body's circadian rhythm, making it easier to fall asleep and stay asleep. Alcohol disrupts sleep architecture later in the night, bright light suppresses melatonin, and intense late exercise can delay sleep onset for some people.

• A. Sleep deprivation makes viruses less infectious
• B. Lack of sleep reduces the body's production of protective cytokines and immune cell activity ✓
• C. Sleep causes the body to produce more mucus, which traps viruses
• D. Poor sleep raises body temperature enough to kill viruses

Why: During sleep, the body produces cytokines and increases the activity of certain immune cells such as T cells and natural killer cells. Sleep deprivation reduces these protective responses, making it easier for a virus to establish infection once exposed.