Association between C-reactive protein and unrecognised sleep-disordered breathing in the elderly

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.In total, 851 (58.5% females) 68-yr-old subjects, who were free of any known cardiac or sleep disorders, were prospectively examined. Subjects underwent unattended polygraphy, and the apnoea/hypopnoea index (AHI) and oxyhaemoglobin desaturation index (ODI) were assessed. Elevated levels of CRP were found on the morning after the sleep study in patients with more severe SDB. A significant correlation was found between CRP levels, time spent at night with arterial oxygen saturation ,90% and ODI. No association was found between CRP levels and AHI. After adjustments for body mass index, smoking status, hypertension, diabetes and dyslipidaemia, a significant association remained between CRP levels and ODI .10 events?h -1 .CRP 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 events?h -1 was the strongest predictor of raised CRP level.The present results suggest that, in the elderly, intermittent hypoxaemia may underlie inflammatory processes leading to cardiovascular morbidity. KEYWORDS: C-reactive protein, elderly, hypoxaemia, inflammation, sleep apnoea O bstructive sleep apnoea syndrome (OSAS) is a highly prevalent disorder affecting 2-4% of the general population and is considered an independent risk factor for cardiovascular diseases [1-3], particularly hypertension, coronary artery disease, heart failure and stroke [4,5]. Furthermore, newly diagnosed OSAS patients, free of classical cardiovascular risk factors, such as hypertension, diabetes and smoking, may have early signs of atherosclerosis [6]. Although the pathophysiology of cardiovascular risk is mutifactorial, sympathetic hypertonia [7], endothelial dysfunction [8, 9] and insulin resistance [10] have been postulated as factors initiating and sustaining inflammatory microvascular alterations and therefore atherosclerosis [11,12]. In middle-aged OSAS patients, C-reactive protein (CRP), a marker of inflammation in atherosclerotic lesions [13], is elevated in severe cases [14] and decreases after treatment with nasal continuous positive airway pressure [15]. Despite the putative role of CRP in cardiovascular risk in OSAS, studies conducted to date have yielded contradictory results, with some showing an independent association with disease severity in adults [16][17][18][19] and children [20,21], and others showing no relationship [22,23]. Moreover, the association between obesity and CRP [24] raised the question as to whether elevated CRP reflects the effects of obesity or whether it is specific to OSAS itself.In the elderly, the prevalence of sleep-disordered breathing (SDB) is estimated to be higher than in middle-aged subjects. AN...

Relationship between C-reactive protein levels and obstructive sleep apnea syndrome

“…In this study, we found that CRP levels in the OSA patients were significantly higher as compared with that in normal individuals. Furthermore, significant differences in CRP levels were detected between mild and severe OSA patients, similar to findings by Roche et al (2009). Previous studies have also found that plasma CRP and IL-6 levels were elevated in patients with OSA.…”

The relationship between high-sensitivity C-reactive protein levels and the severity of obstructive sleep apnea

“…Elevated serum hs-CRP levels have also been reported in OSA patients in previous studies [4,5,13,17,19,27,28]. However, as will be discussed, there are conflicting results regarding hs-CRP levels in OSA patients.…”

“…Increased plasma IL-6 and CRP levels have been noted during hypoxic conditions, and IL-6 is one of the key regulators of CRP synthesis by the liver. Thus, hypoxia may contribute to elevated CRP levels in patients with OSA [5,27]. In other words, it appears that inflammation increases with the severity of OSA.…”

Relationship of oxidative stress and endothelial dysfunction in sleep apnoea

“…Various mechanisms link OSA to an increase in vascular diseases [6][7][8][9].These mechanisms can produce endothelial dysfunction, an early indicator of vascular disease. This is of great epidemiological importance, as it can favour or accelerate the process of atherogenesis and the development of cardiovascular disease [6,8,10,11].…”

“…This is of great epidemiological importance, as it can favour or accelerate the process of atherogenesis and the development of cardiovascular disease [6,8,10,11].…”