Myeloid-related protein-8/14 and C-reactive protein in individuals evaluated for obstructive sleep apnea.
BACKGROUND
Obstructive sleep apnea (OSA) and obesity are often present concomitantly. Their potential contribution to inflammation remains an ongoing debate. The objectives of this study were to investigate whether variables of sleep-disordered breathing are associated with levels of myeloid-related protein-8/14 (MRP-8/14) or C-reactive protein (CRP), and to characterize how adiposity interacts with these associations in individuals evaluated for possible OSA.


METHODS
Consecutive individuals referred to Lovisenberg Diakonale Hospital's sleep laboratory between 1st October 2009 and 1st March 2010 were included. We characterized the biomarker distribution sampled the morning after sleep and related these to clinical characteristics and variables recorded during polygraphy or polysomnography.


RESULTS
Of the total study population of 222 individuals, 161 (72.5%) were diagnosed with OSA (apnea-hypopnea index (AHI) > or = 5/h). In baseline models (multiple median regression adjusted for age and sex), AHI was independently associated with MRP-8/14 (P=0.025) and CRP (P<0.001). The associations were attenuated after the addition of body mass index (BMI), but remained statistically significant for CRP (P=0.025). However, in final models adjusted for additional factors (systolic blood pressure, cholesterol:high-density lipoprotein ratio, glycosylated haemoglobin, smoking, and cardiovascular disease), only average oxygen saturation for MRP-8/14 (P=0.028) and oxygen desaturation index (ODI) for CRP (P=0.037) remained independent predictors of inflammation, whereas AHI lost its predictive value (MRP-8/14; P=0.30 and CRP; P=0.092). The association between several variables of sleep-disordered breathing and inflammation were stronger in individuals with a higher BMI (P for interaction <0.05 for AHI, nadir oxygen saturation, and time <90% oxygen saturation).


CONCLUSIONS
No definitive indication of independent immunological activity resulting from apneas and hypopneas was found in final models adjusted for other factors associated with inflammation, whereas average oxygen saturation for MRP-8/14 and ODI for CRP remained statistically significant predictors. Interactions were observed between BMI and several variables of sleep-disordered breathing on MRP-8/14 and CRP levels.
Department of Cardiology, Lovisenberg Diakonale Hospital, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway. Electronic address: tshall@online.no.
Trygve Sørdahl
TS
Hall
Department of Cardiology, Lovisenberg Diakonale Hospital, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
Tobias Erik
TE
Herrscher
Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
Petr
P
Jarolim
Unit of Biostatistics and Epidemiology, Oslo University Hospital, Oslo, Norway.
Morten Wang
MW
Fagerland
Department of Cardiology, Lovisenberg Diakonale Hospital, Oslo, Norway.
Torstein
T
Jensen
Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Department of Cardiology, Oslo University Hospital, Oslo, Norway.
Stefan
S
Agewall
Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Department of Cardiology, Oslo University Hospital, Oslo, Norway.
Dan
D
Atar
Medical Affairs, Boehringer Ingelheim Norway KS, Asker, Norway.
Jonas
J
Hallén
D000328:Adult; D002097:C-Reactive Protein / Q000032:analysis*; D040501:Calgranulin A / Q000097:blood*; D040502:Calgranulin B / Q000097:blood*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000097:blood*
D040501:Calgranulin A; D040502:Calgranulin B; D002097:C-Reactive Protein
Body mass index; C-reactive protein; Inflammation; Myeloid-related protein-8/14; Obstructive sleep apnea; Sleep-disordered breathing