Keywords
Obstructive sleep apnea syndrome ; Red cell distibution width; Polysomnography (PSG)
Abstract
Objective: The aim of this study was to assess the association between Apnea- Hypopnea ?ndex (AHI) and Red Cell Distribution Witdh (RDW) in patients with Obstructive Sleep Apnea Syndrome (OSAS) and to investigate whether RDW can be a predictor of disease severity before polysomnography.
Methods: This study was designed as retrospective and cross-sectional. Between January 2018 and March 2018, 109 consecutive patients with symptoms of snoring and sleep apnea included in this study.The study population was divided in to four groups:(i) Mild OSAS described as; AHI 5-14.9, (ii) moderate OSAS described as; 15-29.9, (iii) severe OSAS described as; AHI> 30 and (iv) control group decribed as AHI between 0-4.9 according to polyspmnography (PSG). Those with systemic disease that would affect RDW were excluded. Laboratory results and demographig data were extracted retrospectively.
Results: Of the patients included in the study, 83 (76%) were male and 26 (24%) were female. The mean age was 45.3 (43.7 for males and 50.8 for females), the mean Body Mass Index (BMI) was 30.3 (min: 19 - max: 51), the mean AHI was 22.6 (min: 0, max: 103) and the mean RDW was 13.5 (min: 12, max: 15.9). In our study, the RDW value was significantly higher in patients with OSAS compared to the control group. In the subgroup analysis, the highest RDW values were found in the severe OUAS group. Unlike the results from other studies,thelowest RDW value was found in the moderate OSAS group. However, no statistically significant difference was found between the groups. The severity of the disease was not correlated. This may be because the patient population is relatively small or there may be a distribution inequality between groups.
Conclus?ons: There is a relationshipbetween OSAS and RDW but more comprehensive, prospective and multi-centered studies must be performed.
Introductıon
Obstructive Sleep Apnea Syndrome (OSAS) is the most common sleep disordered. In Spain, 3-6% of the population have symptoms of snore with 24-26% of them were above AHI ≥5 and were diagnosed with OSAS [1]. OSAS is characterized by recurrent partial or complete upper airway obstruction resulting in a hypoxia-reoxygenation cycle and arousals during sleep. Hypoxia, the main factor in thepathogenesis, leads to increased hypercapnia and intrathoracic pressure, activation of the sympathetic nervous system, deterioration of cerebral blood flow, elevation of blood pressure and disturbance of sleep. This results inadequate sleep, abnormal motor activity, headache and fatigue [2].
Because of all these metabolic changes, endothelial dysfunction occurs and there is an increased risk of cardiovascular and cerebrovascular events.Tachycardia or rhythm disturbances may occur during sleep [3]. PSG is the gold standard test in OSAS diagnosis. The disease grade is classified according to the AHI values in the polysomnography report. Thosewith AHI ≤ 5 areconsidered as simplesnoring, AHI: 5-14.9 aremild OSAS, thosewith AHI: 15-29.9 aremoderate OSAS, thosewith AHI ≥30 are severe OSAS [4].
RDW shows irregularities between the shapes of erythrocytes.Oxidative stress caused by hypoxia causes irregularity in erythrocyte morphology. In systemic diseases such as iron deficiency anemi, folic acid deficiency, vitamin B12 deficiency and chronic liver disease, RDW levels increase because of oxidative stress [5]. High RDW values are an important biomarker of cardiovascular mortality and morbidity risk, before myocardial infarction [6,7]. Given the inflammatory nature of OSAS, it is thought to be associated with RDW. The aim of this study was to evaluate the association between RDW and AHI in patients with OSAS and to determine whether RDW could be a predictor of disease severity before PSG.
Materials and Methods
The study included 109 patients admitted to Adana City Training and Research Hospital otolarhinolaryngology clinic between January 2018 and March 2018, with a complaint of snoring and symptoms of sleep apnea. All patients underwent PSG in the sleep laboratory of otolarhinolaryngology clinic. Those with any systemic disease that would affect the RDW were excluded from the study.
Patient demographics and laboratory data were recorded. Sleep and physiological variables were monitored with Comet-PLUS Grass® (Astro-MedIndustrial Park, West Warwick, USA) PSG. Electroencephalography can be performed with 10 channels (C3, C4, O1, O2, Fp1, Fp2, F3, F4, P3, P4), submental Electromyography (EMG), right and left eye electrooculography, electrocardiography, oronasal airflow (thermal sensor and nasal transducer), body position, thoracic and abdominal motion meter (inductance plethysmograph), arterial blood oxygen saturation with finger pulse oximetry, left and right leg motion sensors (EMG), and tracheal microphone were used. Apnea was defined as reduction of air flow signal, more than 90% for at least 10 seconds, measured by the thermal sensor. Hypopnea was defined as a reduction in the nasal pressure signal, more than 30% over baseline and resulted in more than 3% desaturation or arousal compared to baseline, for at least 10 seconds.
The study population was divided according to the AHI values; (i) mild OSAS; AHI: 5-14.9 (ii) moderate OSAS; AHI: 15-29.9, (iii) severe OSAS; AHI:> 30. Those with AHI between 0-4,9 were the control group. Statistical analysis was performed with IBM SPSS Statisticsfor Windows, version 22.0 (SPSS Inc., Chicago, IL, USA).AHI and RDW correlations were assessed by Pearson correlation test, RDW value between groups was assessed by Independent Samples test, p <0.05 was considered statistically significant. For the study, permission was obtained from the ethics committee of our hospital.
Results
Of the patients included in the study, 83 (76%) were male and 26 (24%) were female. The mean age was 45.3 (43.7 for males and 50.8 for females), the mean Body Mass İndex (BMI) was 30.3 (min: 19 - max: 51), the mean AHI was 22.6 (min: 0, max: 103) and the mean RDW was 13.5 (min: 12, max: 15.9). Patient characteristics, BMI, AHI and RDW values of the subgroups are given in table 1.
Table 1: Age, BMI, AHI, RDW values of sub groups.
Discussion
OSAS is a syndrome characterized by recurrent partial or complete upper respiratory tract obstruction resulting in a hypoxiareoxygenation cycle and arousals during sleep. Some studies have shown that platelet activation due to the hypoxia-reoxygenation cycle is associated with increased RDW and inflammation. Sinem Medine et al. İnvestigated the relationship between RDW and OSAS in 108 patients. Study population was divided into the three groups; mild, moderateand severe according to the AHI index, Inpatients with severe OSAS (AHI≥30) RDW values werefoundto be significantly higher. Positive correlation was also found between AHI and RDW values [5].
Leon et al. reported a prospectivecontrolledstudyinvolving 138 patients and RDW values in the OSAS group were significantly higher than the controlgroup (p = 0.223). It was also found that AHI was positively related to RDW in patients with OSAS (p = 0.02). Another study by Ozsu et al. reported that RDW values were found to be higher in patients with OSAS in 137 patients. Significant correlation was found between RDW and AHI. Furthermore patients with cardiovascular risk were found to have higher RDW values.
In this study, RDW was thought to be associated with cardiovascular risk in OSAS patients [8]. Kıvanç et al. Examined 300 patientswith OSAS and there relationship between cardiovascular diseases (hypertension, arrhythmia, coronary artery disease)and Neutrophil Lymphocyte Ratio (NLR), Platelet Lymphocyte Ratio (PLR), Mean Platelet Volume (MPV), RDW. Similar to our study, patients divided into three groups; mild, moderate and severe according to their AHI scores and identified patients with AHI ≤ 5 as the control group. NLR, PLR and MPV values were not statistically different among the groups, but the RDW values were significantly higher in patients with cardiovascular risk factors (p≤0.05). As a result of the study, a relationship between OSAS and comorbid diseases were found with increased RDW [9].
Kurt et al. İnvestigated the relationship of OSAS with Mean Platelet Volume (MPV), Platelet Distrubition Width (PDW), C-Reactive Protein (CRP) and RDW in 137 patients. RDW was found to be significantly higher in the group with AHI≥30 but they couldn’t find any relationship with other parameters.This study concluded that AHI did not correlate with CRP, MPV and RDW, but a positive correlation with PDW, showing platelet activation was thought to be a marker of OSAS severity [10]. In our study, the RDW value was significantly higher in patients with OSAS compared to the control group. In the sub-group analysis, the highest RDW values were found in the severe OSAS group.Unlike the results from other studies, the lowest RDW value was found in the moderate OSAS group. However, we did not find statistically significant difference between the groups. The severity of the disease was not correlated with PDW. The explanation of this result may be that the patient population is relatively small ortheremay be a distribution inequality between groups.
Conclusion
RDW increases are seen in patients with OSAS. Furthe comprehensive studies involving a large number of patients are needed to determine its association with AHI and its usefulness as a biomarker.
References
Citation
Karao?ullarindan A and Yal?m SD. Relationshiop between Apnea- Hypopnea Index and Red Cell Distr?bution Witdh in Patients with Obstructive Sleep Apnea Syndrome. SM Otolaryngol. 2018; 2(1): 1015.