Association between inflammation and cognitive function and effects of continuous positive airway pressure treatment in obstructive sleep apnea hypopnea syndrome

Abstract

To explore the association between serum inflammation levels and cognitive function in patients with obstructive sleep apnea-hypopnea syndromes (OSAHS) and evaluate the effects of continuous positive airway pressure treatment (CPAP) on serum inflammation levels and cognitive function. A total of 139 eligible patients were monitored by overnight polysomnography (PSG) at Sleep Center, Second Affiliated Hospital, Soochow University from June 2011 to April 2013. Based on the results of apnea-hypopnea index (AHI), they were divided into 4 groups of primary snoring (n = 18), mild OSAHS(n = 23), moderate OSAHS (n = 29) and severe OSAHS (n = 69). The questionnaires of Montreal Cognitive Assessment (MoCA), Mini-Mental State Examination (MMSE) and Epworth Sleepiness Scale (ESS) were administered to assess cognitive function and daytime sleepiness. The serum levels of high-sensitivity C-reactive protein (Hs-CRP), leptin and tumor necrosis factor alpha (TNF-α) were detected to evaluate systemic inflammation. The questionnaire scores, serum levels of Hs-CRP, leptin and TNF-α and PSG parameters were compared among 4 groups. Thirty-three patients in severe OSAHS group (treatment group) with good adherence were evaluated at baseline and after long-time CPAP treatment. Compared to primary snoring group, the serum Hs-CRP ((1.77 ± 1.19) vs (0.92 ± 0.82) mg/L), leptin ((15.21 ± 13.26) vs (6.35 ± 4.51) mmol/L) and TNF-α ((21.04 ± 7.78) vs (10.30 ± 5.23) pmol/L) levels increased significantly in severe OSAHS group (P < 0.05). After adjusting for body mass index (BMI), age and education years, MoCA scores showed negative correlations with serum TNF-α, AHI, oxygen reduction index (ODI) and TS90% (r = -0.266, -0.236, -0.201, -0.18 respectively, all P < 0.05) and positive correlations with minimum oxygen saturation (LSaO(2)) (r = 0.224, P < 0.05). The evaluations of MoCA subdomains further revealed selective reductions in visual space, executive function, attention and delayed memory function. The treatment group with good adherence to > 6-month continuous positive airway pressure (CPAP) treatment and after CPAP treatment, the serum levels of Hs-CRP, TNF-α and leptin improved markedly ((1.20 ± 0.88) vs (2.03 ± 1.58) mg/L, (14.12 ± 4.34) vs (22.74 ± 6.72) pmol/L and (7.37 ± 5.30) vs (13.69 ± 7.17) mmol/L respectively). The scores of MoCA and ESS also improved (27.79 ± 1.69 vs 24.76 ± 2.57, 4.33 ± 3.14 vs 12.61 ± 5.80 respectively) (all P < 0.01). The score of all MoCA subdomains improved after treatment. Cognitive dysfunction and inflammatory reaction are common in OSAHS patients. MoCA scores are correlated significantly with serum level of TNF-α and nocturnal intermittent hypoxia. Systemic inflammation may play an important role in cognitive dysfunction of OSAHS patients. And long-time CPAP treatment can improve systemic inflammatory response and cognitive impairment.