Hypertension and Sleep Apnoea

Each time your heart beats, it pumps blood through arteries and blood vessels and around your body. With each pulse of blood, the pressure in the arteries rises.  This is called systolic blood pressure.  Between each heart beat, your heart relaxes and refills with blood ready for the next push.

At this time the pressure in your arteries drops.  This lower pressure is called diastolic blood pressure. 

Blood pressure is quoted as two numbers, the systolic and diastolic pressure.  A normal blood pressure is 120/80 (‘120 over 80’).  It’s measured in mmHg or millimetres of mercury.

If your blood pressure is high, it puts extra strain on your arteries and on your heart.  High blood pressure, or hypertension, is defined as a blood pressure higher than 140/90.  This measurement must be taken at rest and repeated over a few weeks before hypertension is diagnosed.

Hypertension often does not produce any obvious signs or symptoms; it is not something you can usually feel.  The only way to know your blood pressure is to have it measured.

Hypertension is one of the most important factors that can increase your chance of developing heart disease, stroke or other serious conditions.  The higher the blood pressure, the greater the strain on the heart and the greater the risk of developing a serious condition. 

Sleep apnoea is known to cause hypertension1.

When someone with sleep apnoea suffers an apnoea or hypopnoea during sleep, the resulting arousal causes activation of the Sympathetic Nervous System (SNS). The activation of the SNS causes the blood vessels to narrow.  Since the heart is now pushing blood through narrowed blood vessels there is extra strain on the heart and the blood pressure is raised.   SNS activity also increases the heart rate which further increases blood pressure.  

In a sleep apnoea sufferer, this can happen hundreds of times during a night’s sleep. Sleep is supposed to be a time when the heart is resting, not running a marathon!  Since blood pressure is consistently increased during the night, it can result in sustained high blood pressure during the day, ie hypertension.

Studies show that about 35% of all people with hypertension have sleep apnoea2,3
About 80% of people taking three or more medications to control their blood pressure have sleep apnoea4.

It has been shown that in patients who are on three or more types of drugs to control their blood pressure, appropriate CPAP therapy reduced night time blood pressure by an average of 10mmHg over 9 weeks.  These patients also showed an overall decrease in blood pressure during the day.

Since these patients do not respond to medication, effective CPAP therapy was a very important addition to their treatment.

By treating sleep apnoea, you may significantly lower your blood pressure and subsequently improve the overall health of your heart.  This will reduce your risk of developing associated serious diseases.

 

References:

1.  JNC7
2. Sjostrom et al, 2002
3. Worsnop et al. Am J Respir Crit Care Med. 1998
4. Logan et al. J. Hypertension. 2001
5. Becker et al. Circulation 2003