When you sleep, do you stop breathing for 10 to 30 seconds at a time? If so, you may not know it, although you may have other tell-tale symptoms suggestive of obstructive sleep apnoea (or apnea) – a condition that is especially common when you have high blood pressure. Sleep apnea may even be the cause of hypertension in many people.
Contents Of This Article
- What is obstructive sleep apnoea?
- The link between sleep apnea and high blood pressure
- Sleep apnoea and resistant hypertension
- What causes sleep apnoea?
- Sleep apnoea symptoms
- David’s experience with sleep apnoea
- Sleep apnoea diagnosis
- Sleep apnoea treatment
- Playing a didgeridoo can tone up your throat muscles
What is obstructive sleep apnoea?
Apnea is defined as the complete cessation of airflow for at least 10 seconds. You literally stop breathing for extended periods while you sleep. This occurs when your upper airway collapses to block the inflow of oxygen to the lungs, and the outflow of waste carbon dioxide gas. The commonest cause is over-relaxation of throat muscles, which allows your upper airway to sag, or your tongue to fall backwards.
The blocked airway usually results in loud snoring and, when complete obstruction occurs, your breathing stops.
When you stop breathing, carbon dioxide builds up in your blood until it is sufficiently high to activate a survival mechanism in your brain. This restarts your breathing and your airway jerks open with a gasp which briefly wakes you, although you probably won’t remember next morning. If you use an activity monitor such as a FitBit, the tell-tale waking spikes will be evident.
These episodes of sleep apnea last for more than 10 seconds and if you have 15 of these events during an hour then you are diagnosed with obstructive sleep apnoea syndrome. In extreme cases, 100 to a 1000 episodes of sleep apnoea can occur per night.
Up to 30% of adults are thought to have sleep apnea, although 85% or more remain diagnosed. Left untreated, lack of oxygen during sleep damages arteries and is increasingly recognised as a cause of essential hypertension.
Untreated obstructive sleep apnoea damages blood vessels in three main ways:
- Intermittent lack of oxygen (hypoxia) leads to inflammation and constriction of arteries, leading to high blood pressure
- Pressure changes within the chest can place excessive mechanical stress on the heart and large artery walls baroreceptor reflexes) leading to high blood pressure
- The nerve reflexes that trigger breathing again when carbon dioxide levels rise activate stress responses (adrenaline and the sympathetic nervous system) causing blood pressure to rise
Studies suggest that at least one in three people with obstructive sleep apnea have high blood pressure and, conversely, at least one in two people with hypertension have obstructive sleep apnoea.
Normally, your blood pressure decreases during sleep by 10% to 20% of your readings while awake, and pressure rises promptly when you wake. Because sleep apnoea often causes momentary waking, the usual nocturnal dip in blood pressure may be absent. Your blood pressure may even be greater at night due to sleep fragmentation, which increases arterial damage.
One of the earliest signs that sleep apnoea is affecting blood pressure may be an increase in diastolic blood pressure (the lower reading) which is the pressure in your arteries while your heart rests between beats.
As well as increasing your risk of hypertension, these circulatory changes mean that obstructive sleep apnea also increases your risk of developing angina, a heart attack, congestive heart failure and stroke.
Sleep apnoea and resistant hypertension
Resistant hypertension, or refractory hypertension, is a high blood pressure that does not come down into the normal range despite taking three different classes of antihypertensive medication, including a diuretic.
Sleep apnea is now recognised as a cause of resistant hypertension (although the most common cause of resistant hypertension is not taking your medication as prescribed).
Studies also show that, the more severe your sleep apnea is, the less likely your blood pressure can be controlled. This effect may due to increased production of a hormone, aldosterone. Aldosterone is produced in the adrenal glands and is involved in regulating blood pressure by reducing the excretion of sodium and water in the kidneys.
Drugs that reduce the secretion or action of aldosterone, such as ACE inhibitors, and spironolactone (a potassium-sparing diuretic) may be most effective in reducing blood pressure in these cases.
What causes sleep apnoea?
Sleep apnea affects one in 20 adults overall and is three times more common in men than in women. Two in three people with sleep apnea are overweight, with a collar size greater than 17 inches (43cm) for men, or 16 inches (41cm) for women. Although excessive fat around the neck can squash the airway during sleep, slim people can develop sleep apnoea, too.
Other risk factors that increase your risk of obstructive sleep apnoea include increasing age, having an underactive thyroid gland, thyroid swelling (goitre), nasal obstructions (eg polyps, deviated septum, allergic congestin), drinking alcohol during the evening, smoking cigarettes and taking sleeping tablets.
Having type 2 diabetes, a condition which is also associated with high blood pressure, also increases your risk of sleep apnoea. One study found obstructive sleep apnea was four times higher in men with type 2 diabetes than in the general population. Some research suggests the majority of people with type 2 diabetes have sleep apnoea.
Sleep apnoea symptoms
You are unlikely to know that you have obstructive sleep apnea unless your bed partner wakes you when snore loudly and then stop breathing, which is scary to witness.
Lack of oxygen and disrupted sleep can cause tell-tale signs which can suggest you are affected, however, such as:
- waking feeling drunk or hung over, even though you’ve had little or no alcohol
- waking with a frightening sensation of choking and fighting for air
- morning headaches
- excessive daytime sleepiness
- constant yawning
- lack of concentration
- poor memory – your thoughts may peter out mid-sentence
- poor driving skills which can lead to accidents
- decreased interest in sex
- erectile dysfunction.
You are also likely to snore loudly, and to fidget a lot at night – ask your bed partner.
Over 40% of people who snore have obstructive sleep apnea.
David’s experience with sleep apnoea
David, 49, started snoring more loudly and frequently. He was always tired, increasingly irritable and his memory so poor his wife started to suspect he had Alzheimer’s. Then one night, she realised he was stopping breathing for scary lengths of time. David also woke with a horrible sensation of not being able to breath. After doing some research, he ordered an at-home sleep apnoea test to use overnight in the comfort of his own bed. A thimble-like clip on one finger connected to a wristwatch-style recording device (Finger Pulse Oximeter) to monitor his oxygen levels, heart rate and snoring while he slept. The results confirmed that he had sleep apnoea. During that one night, David experienced a total of 147 episodes of sleep apnoea (an average of 21 per hour) which lasted around 25 seconds at a time. One obstruction lasted as long as 41 seconds and the level of oxygen in his blood fell as low as 84%. His GP referred him for an ENT assessment, which showed his nasal passages were blocked and he was prescribed a strong corticosteroid decongestant spray. His blood pressure, which was raised, came back down to normal. He now uses a home nasal irrigation system as a drug-free way of reducing nasal congestion, and designed his own throat strengthening exercises which helped to solve the problem.
If you think you could have obstructive sleep apnea, do talk to your doctor as having obstructive sleep apnoea is an important risk factor for high blood pressure, heart failure, coronary heart disease and stroke.
Australian researchers have even found that people with moderate to severe obstructive sleep apnea (15 or more episodes of respiratory disturbance per hour) were six times more likely to die over a 14 year follow-up period than those without sleep apnoea. Milder cases of sleep apnoea (5 to 14 episodes per hour) were not associated with an increased mortality rate, but it’s still important to get diagnosed and treated.
Sleep apnoea diagnosis
While a diagnosis of obstructive sleep apnoea is often made with some confidence based on history and examination alone, the gold-standard test is to have over-night monitoring of your sleep in a procedure known as diagnostic polysomnography (ideally in a sleep laboratory). This involves wiring you up to a number of machines which monitor your brainwaves to assess how often you wake during the night, your muscle tone, chest and abdominal movements, mouth and nasal airflow, blood oxygen levels and your heart rate as well as performing sound and video recordings. These tests are quite involved, and are only available from a few centres. It is therefore more common to have some tests performed in your own home using equipment that monitors blood oxygen levels, heart rate, body movements, oral and nasal airflow and which records snoring noises.
The severity of your sleep apnoea is then classified according to the AHI (apnoea/hypopnoea index) which is calculated from the number of times per night you stop breathing or your blood oxygen levels drug due to significantly reduced air flow. An AHI of 10 or more is likely to cause clinical problems.
Sleep apnoea treatment
Sometimes, diet and lifestyle advice is all that’s needed, and some of these approaches will help to lower a high blood pressure, too. The following tips can help to improve obstructive sleep apnoea:
- Lose any excess weight
- Avoid alcohol
- Avoid sleeping tablets
- If you smoke, do your utmost to quit
- Take regular exercise
- Learn to play the didgeridoo
- Use anti-snoring devices and sprays
- Raise the head of your bed 10 cm to help stop your tongue flopping back
- Sleep on your side rather than your back
- Treat acid reflux and heartburn to reduce spasm of airway
- Use a humidifier (if your airways are dry) or an air purifier (if you have allergies) in your bedroom to make breathing easier.
Weight loss and physical activity can improve muscle tone and reduce obstructive sleep apnoea – a 10% weight loss, for example, can improve the AHI assessment by 26%.
Playing a didgeridoo can tone up your throat muscles
If you’ve always wanted to play the didgeridoo, you now have an excellent excuse to take it up. Regularly playing the didgeridoo can improve snoring and sleep apnoea by strengthening throat muscles in the upper airway so they are less likely to collapse.
A study involving 25 people with sleep apnoea (AHI score between 15 and 30) and snoring, involved taking didgeridoo lessons with daily practice at home for four months. Those taking part played the didgeridoo, for 25 minutes, 6 days a week. Compared to a control group who remained on the waiting list to start didgeridoo lessons, daytime sleepiness reduced, and their AHI score reduced by 6.2 and their partners reported less sleep disturbance.
Mild to moderate sleep apnoea may respond to wearing an oral dental appliance. These are worn in the mouth at night rather like a sports’ mouth guard, and are of three main types:
- mandibular repositioners which move the jaw forwards to help stop the tongue falling backwards
- tongue retainers which hold your tongue to keep it forwards
- equalisers which lift your soft palate or uvula (the dingly-dangly blob-on-a-stalk hanging the back of your throat) to help keep your airway open.
In more severe cases, treatment involves continuous positive airway pressure (CPAP) in which a special mask forces air into your nose to keep the airway open. Not everyone tolerates wearing these masks well, however.
Surgery is sometimes needed to enlarge the airway and correct anatomical obstructions such as a deviated nasal septum, nasal polyps, enlarged tonsils/adenoids, a floppy soft-palate, enlarged uvula or tongue.
In some countries the stimulant drug, modafinil, is licensed to treat excessive sleepiness in people with obstructive sleep apnoea (OSA).