Association between CRP and unrecognised Sleep-Disordered Breathing in the elderly

¹ Service de Physiologie Clinique et de l'Exercice, CHU Nord
² Division of Primary Care Medicine, Dept of Community Medicine and Primary Care, University Hospitals, Geneva, Switzerland
³ Faculté de Médecine Jacques Lisfranc, Université Jean Monnet, Saint-Etienne, France

^* To whom correspondence should be addressed. E-mail: Frederic.Roche{at}univ-st-etienne.fr.

	Abstract

Elevated levels of C-reactive protein (CRP) have been reported in patients with sleep-disordered breathing (SDB) and may represent an inflammatory marker of cardiovascular risk. However, the association of CRP with SBD in presumed healthy elderly subjects is unknown. 851 subjects (58.5% women) 68 years old, free of any known cardiac or sleep disorders, were prospectively examined. Subjects underwent unattended polygraphy and the Apnoea/Hypopnoea Index (AHI) and the Oxyhaemoglobin Desaturation Index (ODI) were assessed. Elevated levels of CRP were found in the morning after sleep study in patients with more severe SDB. A significant correlation was found between CRP levels, time spent at night with SaO₂<90% (rho=0.078, p=0.03), and ODI (rho=0.12, p=0.006). No association was found between CRP levels and AHI. After adjustments for BMI, smoking status, hypertension, diabetes and dyslipidemia, a significant association remained between CRP levels and ODI>10.

C-reactive protein levels were frequently increased in a large sample of elderly subjects free of major cardiovascular disease. CRP levels were not correlated with the AHI and the indices of sleep fragmentation, the ODI>10 being the strongest predictor of raised CRP level. These results suggest that, in the elderly, intermittent hypoxemia may underlie inflammatory processes leading to cardiovascular morbidity.