- Sleeping too little or too much are associated with impaired immunity and increased inflammation
- Poor quality sleep is also likely to worsen immune function
It is likely that sleeping too little, or having poor sleep, and possibly sleeping too long impact immunity. There are strong associations between sleep length and quality and a range of long-term health outcomes, such as1:
- Diabetes mellitus
- Cardiovascular diseases
- Coronary heart diseases
Over 70 studies featuring more than 50000 participants have evaluated the effects of sleep deprivation on markers of immunity and inflammation. Sleep disturbance was associated with higher levels of c-reactive protein, and the inflammatory cytokine interleukin 6 (IL-6). Shorter sleep duration was associated with higher levels of c-reactive protein, but not IL-6. Long sleep durations (>9 hours) were also associated with increased inflammation marked by higher c-reactive protein, and IL-6. Interestingly, neither long nor short sleep or sleep disturbance were associated with increased levels of tumour necrosis factor-α, one of the key markers of autoimmune inflammatory conditions like Crohn’s disease.2
C-reactive protein in particular also has an association with over-reaching and over-training in athletes, who also experience frequent colds and flu-like viruses and excessive stress-markers like this suppress some of the normal immune responses.
In summary, poor-quality sleep reduces our ability to properly modulate our immune function.
1. Itani O, Jike M, Watanabe N, Kaneita Y. Short sleep duration and health outcomes: a systematic review, meta-analysis, and meta-regression. Sleep Medicine. 2017;32:246-56.
2. Irwin MR, Olmstead R, Carroll JE. Sleep Disturbance, Sleep Duration, and Inflammation: A Systematic Review and Meta-Analysis of Cohort Studies and Experimental Sleep Deprivation. Biological Psychiatry. 2016;80(1):40-52.