Major risk factors for obstructive sleep apnea monitored in the home. A cross-sectional study

ABSTRACT BACKGROUND: Obstructive sleep apnea (OSA) is characterized by recurrent pharyngeal wall collapse during sleep caused by anatomical or functional changes associated with obesity or dislocation of maxillofacial structures. OBJECTIVE: To determine the major risk factors for obstructive sleep apnea monitored in the home. DESIGN AND SETTING: Cross-sectional study conducted in a private clinic in Fortaleza (CE), Brazil. METHODS: Between 2015 and 2018, 427 patients were screened for OSA with home-based monitoring, yielding 374 positives. Information was collected on age, sex, body mass index (BMI), hypertension, diabetes (DM), dyslipidemia, coronary artery disease (CAD), arrhythmia, peripheral artery occlusive disease (PAOD), heart failure (HF) and lung disease. The home sleep apnea test result was then compared with the clinical diagnosis. Lastly, parameters identified as significant in the univariate analysis were subjected to multivariate logistic regression. RESULTS: Male sex predominated, although not significantly. OSA was associated with hypertension, DM, dyslipidemia, age and BMI. The risk of OSA being associated with these parameters was 2.195 (hypertension), 11.14 (DM), 2.044 (dyslipidemia) and 5.71 (BMI). The association was also significant for BMI categories (normal, overweight or obese). No significant association was observed for CAD, arrhythmia, PAOD, HF or lung disease. After multivariate logistic analysis, only age and BMI (and its categories) remained significant. CONCLUSION: OSA was associated with hypertension, DM, dyslipidemia, age and BMI in univariate analyses, but only with age and BMI (and its categories) in multivariate logistic analysis.


INTRODUCTION
Obstructive sleep apnea is characterized by recurrent pharyngeal wall collapse during sleep, caused by anatomical or functional changes associated with obesity or dislocation of maxillofacial structures. 1 This condition is highly prevalent in patients with cardiovascular disease. In fact, the syndrome is accompanied by hypoxia, oxidative stress, sympathetic activation and endothelial dysfunction, all of which are mediators of cardiovascular disease. 2 Moreover, several authors in the literature have stated that ageing affects the severity of obstructive sleep apnea syndrome and the associated cardiovascular risk. 3 The relationship between obstructive sleep apnea and cardiovascular disease involves the mechanisms of platelet activation and inflammation. Therefore, abnormalities may be observed in laboratory tests based on markers for platelet activation and inflammation, such as mean platelet volume, platelet-lymphocyte ratio, red blood cell distribution width and neutrophil-lymphocyte ratio. 4 The incidence of obstructive sleep apnea is 14% in men and 5% in women. The condition is diagnosed through a sleep study, and the gold standard for this is polysomnography. Because very few clinics offer this type of examination, the vast majority of cases (80%-90%) will most likely never be formally diagnosed. As a cheaper alternative, home-based monitoring may be performed without the presence of a technician. 5 There is evidence to suggest the existence of an association between obstructive sleep apnea and metabolic syndrome or diabetes. 6 The pathophysiology is not well understood, but intermittent hypoxia is likely to play an important role. 7 In addition to hypoxia, sleep fragmentation leads to activation of the sympathetic nervous system, the hypothalamic-pituitary-adrenal axis and pro-inflammatory pathways or oxidative stress. 8  Among cardiovascular disorders, obstructive sleep apnea predisposes to arrhythmia, including atrial fibrillation, which is diagnosed in 6% of obstructive sleep apnea patients (20% if male).
Greater prevalence of atrial fibrillation is positively associated with greater severity of obstructive sleep apnea. 10 In association with obstructive sleep apnea, QT prolongation is a risk factor for severe arrhythmia. 11 The fact that obstructive sleep apnea predisposes to coronary disease is supported by data from a systematic review of three trials, which showed that 12% of 5,067 obstructive sleep apnea patients had myocardial infarction or stroke or needed myocardial revascularization, with a fatality rate of 25% Obstructive sleep apnea is also highly prevalent among Iranians and, in one study, was associated with cardiovascular disease (26%) and systemic arterial hypertension (74%). 16

OBJECTIVE
To determine the major risk factors for obstructive sleep apnea monitored in the home.

METHODS
Between April 2015 and April 2018, we screened 427 patients for obstructive sleep apnea through home-based monitoring.
The result was positive for 374 and negative for 53 ( Table 1).
We also collected information on sex, age, body mass index (BMI) and diagnoses of obstructive sleep apnea, diabetes,

RESULTS
Male sex was predominant, although not significantly (     17 We found that occurrences of obstructive sleep apnea were associated with diabetes, like in many other studies. 5,6 However, we did not find any association with arrhythmia, which is a frequently reported association. Furthermore, we did not find any evidence of the otherwise well-documented fact that obstructive sleep apnea predisposes to coronary artery disease, 12 but the latter was unusually severe in our sample (49 out of 53 coronary artery disease patients had previously been revascularized through surgery or stent implantation).
Another frequently reported association, between systemic arterial hypertension and obstructive sleep apnea, was confirmed in the present study. 13 Moreover, the estimated risk of this association was very high (2.195