The present study is the first large data set furnishing information regarding the prevalence of obstructive sleep apnoea in patients with hypertension from this part of the world. The target population was identified on the basis of physician detected hypertension and the patient data was collected by a standardized protocol on snoring, daytime sleepiness, BP and other features associated with OSA.
Our study demonstrates that OSA is widely prevalent in patients with hypertension. On the basis of standard Berlin Questionnaire, 24% of the test population was found to be at high risk for OSA (i.e., 1 in every 4 hypertensive individuals). This is in accordance with the studies by Peppard and colleagues who identified 24-28% prevalence of OSA in hypertension .
The prevalence of daytime sleepiness in this sample was 62.5% by the Epworth Scale result above 10 points. This prevalence in our sample is in agreement with the prevalence identified in a previous report of patients with hypertension [62.78% (95% CI 58.08 to 67.47)] .
The overall mean age of the high risk for OSA respondents was 53.4 ± 9.02 years. The prevalence of OSA was highest between 51-60 years of age and this risk increased exponentially from 0.8% at ≤ 30 years of age to 41.7% at 51-60 years of age (p ˂ 0.001) (Figure 2). This finding is in agreement with the previous studies demonstrating the effect of age on OSA status , .
The seventh report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure identifies the independent role of OSA in the development of hypertension and its association with obesity . In our study, patients with high-risk of OSA had significantly higher BMI, WC, WHR and NC values compared to the patients with low-risk of OSA (Figure 3). All of the anthropometric indices (NC, WC, and BMI) were significantly correlated with the risk of OSA. These results are supported by similar findings by Kang and colleagues, who reported that NC [95% CI; p < 0.001], WC (95% CI; p < 0.001), and BMI (95% CI; p < 0.001) were significantly associated with the presence of OSA . Hiestand et al. reported that among obese subjects (BMI ≥ 30kg/m2), 59% of subjects were at high-risk of OSA . In our study, only 37.5% of subjects were at high-risk of OSA among obese patients (BMI ≥ 30 kg/m2).
In a study by Endeshaw and colleagues the mean BP values among older adults with sleep-disordered breathing were 133±16 and 71±8 mm Hg for systolic and diastolic BP, respectively (p < 0.001) . In our study, the average systolic and diastolic BP was 133.52 ± 17.503 and 84.37 ± 7.425 mm Hg (Figure 4).
In our study, OSA was found to be strongly associated with resistant hypertension. Though our sample size was not large enough to justify a meaningful conclusion on this, another case-control study by Gonçalves et al. reported that OSA is a strong independent risk factor for resistant hypertension .
Strength of the Study
This is the first population-based, cross-sectional study to determine the prevalence of high-risk of OSA in patients with hypertension from the state of Jammu and Kashmir. This study represents an advanced approach in the understanding of the risk-factors of hypertension and gives an insight into the prevalence of high-risk of OSA in patients with hypertension. The Berlin Questionnaire, used in our study, is a validated instrument that has been used widely to identify individuals who are at risk for OSA . Our assessment of excessive daytime sleepiness was based on the ESS score, which is a well-tested international instrument for the evaluation of daytime sleepiness . With the increasing problem of hypertension, the impact of undetected or under-diagnosed OSA as a healthcare burden cannot be undermined. Therefore, this study can help reduce CV outcomes and healthcare costs of rigorous anti-hypertensive regimen by treating the underlying cause.
Limitations of the Study
The limited number of patients and less time duration are the limitations of this study. Also, we only used the Berlin Questionnaire to identify high risk for OSA. Although polysomnography is the gold-standard test for the diagnosis of OSA in clinical settings , it is complex, expensive, time consuming and uneconomical for the general population. Further studies using overnight polysomnography are needed to exhaustively elucidate the bidirectional association between OSA and hypertension and also to determine the magnitude of prevalence of the two disorders together from different healthcare facilities of the state.