Treatment of sleep apnoea helps in hypertension control The human upper airway functions as a passage for breathing, speech and swallowing of food and liquids. The upper airway is therefore designed without any bony support so that it is flexible. This passage is made up of several soft tissues and muscles and is collapsible and thus allows different functions during wakeful hours. Collapse of this passage during sleep due to sleep induced loss of muscle tone or due to any defect in this framework such as fat deposition around the passage or a large soft palate or tongue or abnormal facial tissues can lead to apnoea/choking during sleep. Obstructive sleep apnoea
Treatment of sleep apnoea helps in hypertension control
The human upper airway functions as a passage for breathing, speech and swallowing of food and liquids. The upper airway is therefore designed without any bony support so that it is flexible. This passage is made up of several soft tissues and muscles and is collapsible and thus allows different functions during wakeful hours.
Collapse of this passage during sleep due to sleep induced loss of muscle tone or due to any defect in this framework such as fat deposition around the passage or a large soft palate or tongue or abnormal facial tissues can lead to apnoea/choking during sleep.
Obstructive sleep apnoea(OSA) is the choking sensation at night where lack of oxygen repeatedly wakes one up from sleep to gasp and open the airways. Waking up is a protective mechanism to help open the airways.
Sleep apnoea is an important cause of secondary hypertension
OSA has been identified as an independent factor that causes high blood pressure (hypertension) and therefore raises the likelihood of death from heart-related problems.
Low oxygen levels activate autonomic nervous system and other hormonal systems (rennin angiotensin) that control the blood pressure. This leads to narrowing of blood vessels and causes other changes in the body that increase the blood pressure.
Nearly half of the patients with OSA suffer from or develop hypertension, as against one- third of those from the general population. The strength of evidence linking OSA with the development of hypertension has been so strong that it led the Joint National Committee on High Blood Pressure (JNC-VII) to list sleep apnoea as an important cause of secondary hypertension.
A study published in the New England Journal of Medicine conducted over middle age adults reported that those not treated for OSA had two- to three-fold higher risk of developing hypertension over a 4 to 8 year period. Eventually, this group of patients also had a higher risk of developing heart disease compared to general population.
Further, a large Canadian population-based study reported that every episode of apnoea in an hour increased the likelihood of developing high blood pressure by 1%. Also, for every 10% fall in the nighttimes’ oxygen level, the chance of developing hypertension increased by 13%. The Sleep Heart Health Study found that more severe the OSA higher was both - the systolic (higher reading) and diastolic (lower reading) blood pressure and consequently the mean BP at night.
Fig. 1: Cumulative incidence of hypertension in participants without OSA and untreated patients with OSA, adapted from original article in JAMA, 2012
Likewise, the frequency of high blood pressure increased in direct proportion with the presence and severity of OSA. In these individuals with OSA, the blood pressure continued to remain elevated even during day-time despite normal breathing. 2,6,7 Patients with hypertension may end up with serious consequences such as stroke (paralysis), dementia, heart disease, kidney disease, etc., but often, the treatment of modifiable risk factors of high blood pressure are not even looked for or treated even when known. If the patient has symptoms of heavy snoring and repeated wakefulness at night, these must not be ignored. These patients need immediate sleep study and treatment of OSA to reduce the risk of high blood pressure and its other inherent problems.
Benefits of OSA treatment in hypertension control
OSA is a treatable risk factor for hypertension and continuous positive airway pressure (CPAP) is the standard treatment for OSA; however, it may also be treated surgically.
CPAP provides a gentle stream of air that prevents the airways from collapsing and thus maintains breathing during sleep. Several studies have demonstrated that in people who have moderate-to-severe sleep apnoea, treatment with nasal continuous positive airway pressure (NCPAP) lowers blood pressure during both day and night.
In a randomised study (HIPARCO trial) conducted at several centres, patients with OSA and high blood pressure who had failed to respond to conventional treatment, CPAP therapy for 12 weeks caused reduction in 24-hour mean and diastolic blood pressure and improved the blood pressure pattern at night.
Some studies found that the effect of CPAP treatment on blood pressure levels is dependent on the number of hours of CPAP use. A minimum of 4 hours of use of CPAP per night was associated with a significant decrease in the blood pressure levels.
CPAP use led to a reduction in blood pressure among all the patients irrespective of whether they used anti-hypertensive medication; which means that even those patients who were believed to be well controlled with medicines experienced further reduction in their blood pressure levels, and any decrease in the blood pressure level, even as low as 2 units led to a considerable decrease in the risk of death from various heart and circulatory disorders. Often, patients who for any reason refuse or are non-compliant with CPAP are offered the untested clinical advice of night-time supplemental oxygen as salvage therapy. The evidence points out that beneficial effects of CPAP on blood pressure is not seen with the use of supplemental oxygen even though adherence was greater among patients receiving supplemental oxygen.
Further, use of CPAP has also been effective in reducing sleep apnoea symptoms such as snoring and other co-morbidities like diabetes that are often associated with sleep apnoea. CPAP, thus, currently seems as a preferred non-invasive approach for treatment of OSA with beneficial effects on lowering the blood pressure and the associated heart problems, and reducing the death risk from heart problems too.