Quick Answer: Poor sleep is linked to higher levels of inflammation markers such as CRP and IL-6, but the effect is small. A large meta-analysis found insomnia-type sleep disturbance and very long sleep, but not short sleep itself, were linked to higher markers. Lab trials are mixed. Treating insomnia with CBT-I may lower CRP, though the evidence is limited.
Check how your sleep stacks up with our insomnia severity calculator.
What Is Inflammation And How Is It Measured?
Inflammation is part of the body’s defense system, and doctors track it with blood markers. The studies below measured C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF). Higher levels of these markers can signal ongoing, low-grade inflammation.
Keep in mind that a marker is not a disease. A small rise in a blood test does not mean you are sick. To see how sleep affects defense against infection, read can good sleep improve your immune system.
What Does The Big Meta-Analysis Say?
A meta-analysis pooled 72 studies with more than 50,000 people. Sleep disturbance, such as insomnia complaints, was linked to higher CRP (effect size 0.12) and IL-6 (0.20). Shorter sleep duration was linked to higher CRP (0.09) but not to IL-6. Very long sleep was linked to higher CRP (0.17) and IL-6 (0.11). Neither sleep disturbance nor sleep duration was linked to TNF (Irwin and colleagues).
The authors concluded that sleep disturbance and long sleep duration, but not short sleep duration, are associated with higher markers of systemic inflammation. They found some variation between studies but no sign of publication bias.
| Exposure | CRP | IL-6 | TNF |
|---|---|---|---|
| Sleep disturbance | Higher (0.12) | Higher (0.20) | No link |
| Shorter sleep | Higher (0.09) | No link | No link |
| Very long sleep | Higher (0.17) | Higher (0.11) | No link |
Why Do Studies Disagree?
Designs differ. Surveys follow many people in daily life and rely on self-reported sleep, while lab trials control sleep tightly but use small groups for a short time. The meta-analysis authors noted some variation among studies. The lab trials here enrolled 18 and 30 people, so a few individuals can shift the result.
Different markers also respond differently. In the 18-person trial, IL-6 rose significantly while CRP only trended up, and a TNF marker did not move. A single marker alone gives an incomplete picture.
Are These Effects Big?
No. Effect sizes of 0.09 to 0.20 are small by usual statistical conventions, so sleep explains only a modest part of why inflammation markers differ between people. Age, weight, illness and many other factors also matter.
These were mostly observational studies, which show a link and not a cause. People who are ill or stressed may both sleep badly and have higher markers, without one causing the other.
What Happens When Researchers Cut People’s Sleep?
Experiments give a mixed picture. The same meta-analysis found that neither experimental sleep deprivation nor sleep restriction was associated with CRP, IL-6 or TNF when results were pooled. Yet individual trials found changes.
In a 16-day lab study, 18 volunteers slept either 8 or 4 hours a night for 12 days. IL-6 was higher in the 4-hour group (P below 0.05). CRP showed the same trend but did not differ significantly, and a TNF marker was unchanged. Higher IL-6 went with higher pain ratings (Haack and colleagues, 2007).
How Were The Lab Studies Run?
In the 16-day study, volunteers were randomly assigned to sleep 8 or 4 hours a night for 12 days. Blood was drawn frequently on a baseline day and again after the 10th experimental day, over 25 hours. The team measured IL-6, CRP, a TNF receptor marker and urinary prostaglandin metabolites, plus ratings of mood and pain.
IL-6 rose in the 4-hour group, and the rise was strongly tied to higher pain ratings (r = 0.67). The authors reported that this link could not be explained by tiredness or fatigue. A prostaglandin metabolite also rose in 4-hour sleepers, but it did not differ significantly from the 8-hour group.
Does Recovery Sleep Undo The Change?
It may, at least for IL-6. In another lab study, 30 healthy young adults had 4 nights of 8 hours, then 6 nights of 6 hours, then 3 recovery nights of 10 hours. Their 24-hour IL-6 levels rose during restriction and returned to baseline after recovery sleep. Sleepiness also recovered, but performance did not (Pejovic and colleagues).
In that study, the cortisol stress hormone did not change during restriction but was significantly lower after recovery. The participants were healthy young adults averaging 24.7 years old, so older or sicker people could respond differently.
That is a useful reminder: one mild week of short sleep changed a marker, and two nights of long sleep brought it back, yet thinking performance stayed down. See how to recover from sleep debt for a plan.
Can Treating Insomnia Lower Inflammation?
There is some evidence. In a randomized trial of 123 older adults with insomnia, cognitive behavioral therapy for insomnia (CBT-I) reduced CRP compared with a sleep education group at months 4 and 16. CBT-I also reduced expression of genes that drive inflammation (Irwin and colleagues, 2015).
Learn more about the therapy in CBT-I. The trial had three groups: CBT-I, tai chi chih and a sleep education group, each meeting for two-hour sessions weekly over 4 months, with follow-up at 7 and 16 months. Tai chi chih also lowered cellular inflammatory responses, which shows that more than one approach may help.
A later systematic review of 15 studies with 2,067 people found that CRP was lower with CBT-I in three studies, but effects on IL-6 and TNF varied or were null. Five of the 15 studies had high risk of bias, so the authors said this limits how far the findings can be trusted.
Why Does This Topic Matter?
Sleep problems are common. The meta-analysis authors note that about 25 percent of people in the United States report insomnia complaints. If sleep problems nudge inflammation up even slightly, that could matter across a lot of people, which is why researchers keep studying it.
The review of CBT-I trials adds an interesting point. CBT-I was most consistently linked to better HbA1c, a blood sugar measure, and CRP. The authors suggest these are fairly stable markers, so the changes may reflect lasting habit change and not short-term effects. It is a reasonable idea, but it is only a suggestion.
What Does This Mean For Disease Risk?
Be careful here. The sources show markers moving a little, not that poor sleep causes inflammatory disease. The meta-analysis introduction says that sleep problems influence inflammatory disease risk and mortality, but the studies in our set did not test disease outcomes directly.
For related topics, see sleep loss and pain, since the pain link in the 4-hour study tied higher IL-6 to higher pain ratings.
What Can You Do?
These are practical steps built from the studies:
- Protect regular sleep. Both insomnia and very long sleep were linked to higher markers.
- Catch up after short stretches. IL-6 recovered after extra sleep in one study.
- Treat long-term insomnia. CBT-I may also lower CRP, per one trial.
- Do not self-diagnose from a blood test. Ask a clinician to interpret CRP.
- Keep a steady routine. Our sleep hygiene 101 guide helps.
When To See A Doctor
Talk to a doctor if you have trouble sleeping for weeks, you sleep much longer than usual and still feel tired, you have frequent infections or pain, or a blood test shows high CRP.
If low mood comes with thoughts of self-harm, call or text 988 in the US.
FAQs About Sleep And Inflammation
Does Lack Of Sleep Cause Inflammation?
Sleep disturbance is linked to higher CRP and IL-6 in a large meta-analysis, but the effect is small and lab trials are mixed.
Which Inflammation Markers Are Affected?
CRP and IL-6 were linked to sleep disturbance. TNF showed no link.
Is Too Much Sleep Also A Problem?
Very long sleep was linked to higher CRP and IL-6 in the meta-analysis. It is an association and may reflect other health issues.
Can You Reverse The Effect With Sleep?
In one lab study, IL-6 returned to baseline after recovery sleep.
Does CBT-I Reduce Inflammation?
A trial in older adults found lower CRP after CBT-I. A review found mixed results for other markers and flagged bias risk.
Is The Effect Large?
No. The reported effect sizes were 0.09 to 0.20, which are small.
Can Poor Sleep Cause Disease Through Inflammation?
The studies here do not show that. They show small changes in blood markers.
Sources
- Sleep disturbance, sleep duration, and inflammation: a systematic review and meta-analysis of cohort studies and experimental sleep deprivation
- Elevated inflammatory markers in response to prolonged sleep restriction are associated with increased pain experience in healthy volunteers
- Effects of recovery sleep after one work week of mild sleep restriction on interleukin-6 and cortisol secretion and daytime sleepiness and performance
- Cognitive behavioral therapy and tai chi reverse cellular and genomic markers of inflammation in late life insomnia: a randomized controlled trial
- The effect of cognitive behavioral therapy for insomnia (CBT-I) on cardiometabolic health biomarkers: a systematic review of randomized controlled trials