Diurnal variability of C-reactive protein in obstructive sleep apnea

Sleep Breath. 2009 Nov;13(4):415-20. doi: 10.1007/s11325-009-0268-0. Epub 2009 Jun 17.


Objective: The objective of this study is to examine the diurnal variability of C-reactive protein (CRP) in obstructive sleep apnea (OSA).

Methods and measurements: Participants included 44 women and men with untreated OSA (mean apnea/hypopnea index = 37.5, SD +/- 28) and 23 healthy adults with no OSA. Sleep was monitored with polysomnography in the University of California San Diego General Clinical Research Center. Over a 24-h period, blood was collected every 2 h, and CRP levels were determined.

Results: Adjusting for age, gender, and body mass index, a significant group by time interaction showed that patients with OSA had higher CRP levels during the daytime (8:00 a.m.-8:00 p.m.) versus the nighttime (10:00 p.m. until 6:00 p.m.; p < 0.001). Non-apneics showed no significant change in CRP levels during the 24 h.

Conclusions: The findings indicate that sleep apnea patients have disproportionately elevated CRP levels in the day versus the nighttime, possibly as a result of carryover effects of nighttime arousal into the daytime.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Arousal / physiology
  • Body Mass Index
  • C-Reactive Protein / metabolism*
  • Circadian Rhythm / physiology*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Polysomnography
  • Reference Values
  • Sex Factors
  • Sleep Apnea, Obstructive / immunology*


  • C-Reactive Protein