Sleep-disordered Breathing in Uncontrolled Blood Pressure : Our Experience

Introduction: Sleep-disordered breathing is one of the greatest health problems. It comprises of obstructive sleep apnea, central sleep apnea, periodic breathing, and upper airway resistance syndrome. There are several studies reporting association of uncontrolled blood pressurewith individuals having sleep disordered breathing. Data regarding this were sparse in developing countries. Therefore this study was performed to find out the sleep-disordered breathing among uncontrolled hypertensive patients.

Sleep-disordered breathing (SDB) comprises obstructive sleepapnea (OSA), central sleep apnea &upper airway resistance syndrome.OSA is characterized by reduction in upper airway muscle tone resulting in repetitive complete (apnea) or partial (hypopnea) upper airway closure.OSA results in increased sympathetic nervous system activation, changes in baroreceptor function, increased oxidative stress, and endothelial dysfunction which can increase blood pressure. 1evations in blood pressure (BP) often progresses to hypertension (HTN).In the Framingham Heart Study, high-normal BP was associated with an approximatelytwo-fold increase risk of cardiovascular disease (CVD). 2,35][6] It is unclear whether OSA severity level confers increased risk for elevated BP in our setting.Therefore this study was done to know the severity of sleep disordered breathing in patient with uncontrolled blood pressure.

MATERIALS AND METHODS
This is a hospital-based cross-sectional study from January, 2014 to January, 2017 done in Swacon International Hospital and Sleep Care Center, Kathmandu, Nepal.Permission was obtained from ethical committee.Patients referred from different centers in Kathmandu who had uncontrolled hypertension were included and those withcongestive cardiac failure (ejection fraction <30%) and acute coronary syndromes were excluded.
Out of the total, 250 patients with uncontrolled hypertension were included.Subjects were recruited using Epworth Sleepiness Scale (ESS) questionnaire.All the patients were evaluated by cardiologist and ophthalmologist.Elevated BP was defined a systolic Blood Pressure (SBP) ≥ 130 mmHg or Diastolic Blood Pressure (DBP) ≥ 80mmHg.Uncontrolled elevated BP was defined as SBP ≥ 130mmHg or DBP ≥ 80mmHg without use of an intensive antihypertensive regimen IAR (≥ 3 antihypertensive with 1 being a diuretic).Controlled BP was defined as SBP < 130 mmHg or DBP <80mmHg.Demographic data including age, sex, Body Mass Index (BMI), history of diabetes, smoking history, andmedication for hypertension were collected in structured Performa after informed consent.Subjects who met inclusion criteria underwent overnight level IV polysomnographic test using ALICE 5 done in sleep lab after written consent.Polysomnography reporting was done by certified sleep physician.

Statistical Analysis
Analysis was performed using a statistical software package (SPSS 22 for windows).Nominal variables were compared using Chi-square test or Fisher's exact test.
Step wise multivariate logistic regression was performed with potential candidate variables as covariates.All the statistical tests performed were two tailed; p<0.05 was considered statistically significant.

DISCUSSION
The main finding of this study was that SDB is more prevalent in hypertensive men.The results confirm the findings of previous smaller studies in which hypertensive and non-hypertensive subjects have been compared for the prevalence of SDB. 4,5,7,8letcher and coworkers compared 46 hypertensive men taken off medication with 34 age and weight matched normotensive control subjects.An Apnea-Hypopnea Index (AHI)>10 was found in 30% of the hypertensive subjects and in 9% of the controls. 9In the Sleep Heart Health Study, a prospective population-based cohort, study patients with AHI>15 had three times the odds of having hypertension at baseline compared to controls.After adjusting for demographics and anthropometric variables, odds ratio (OR) for hypertension for those with AHI ≥30 was 1.37 (95% confidence interval (CI), 1.03-1.83).2HeartBiomarker Evaluation in Apnea Treatment (HeartBEAT) study, a 4-site randomized controlled trial, found 3-fold higher odds of resistant elevated BP (OR 2.75, 95 % CI 1.23-6.14,p = 0.01) in the severe OSA group in the model adjusted for age, sex, race, BMI, smoking, diabetes mellitus, and CVD. 10 Limitation of this study is that the BP was measured only once in outpatient visit in most of the participants.Twenty four hour ambulatory BP monitoring may help to provide prognostic value.

Table 1 Characteristics of patients with uncontrolled hypertension n=250Table 2 : Obstructive sleep apnea in uncontrolled hypertensive patients (n=250)Table 3 : Logistic regression of Severe OSA with uncontrolled blood pressurepatients (n=250)
Sijapati MJ et al