The association between high blood pressure (hypertension) and increased risk of cardiovascular events, such as heart attacks and stroke, is well established. However, recent studies have highlighted a link between poor quality of sleep, hypertension and cardiovascular events, and challenge current diagnostic testing and potential treatments.
High blood pressure is a well-known risk factor for cardiovascular events. Diagnosis of high blood pressure (hypertension) and clinical decisions regarding its treatment have typically been based upon daytime blood pressure measurements. However, as ambulatory 24-hour assessments of blood pressure became more accessible, it became increasingly apparent that high blood pressure during the night, could be even more detrimental to cardiovascular health 1 . Blood pressure displays a rhythmic (circadian) change over the day-night period that is controlled by the biological clock and sleep 2 3 . Thus, blood pressure is usually high during the day and normally decreases by 10% or more during night time sleep (‘dipping’). Some people are defined as ‘non-dippers’ because their blood pressure does not decrease enough during sleep. Higher-than-normal overnight blood pressure may lead to injury to blood vessels of the brain, eye, kidney, and heart and to the development of cardiovascular disease.
Other studies have looked into possible reasons for hypertension and came up with a seemingly surprising observation that short sleep duration and even more so, poor sleep quality, greatly increase the risk for developing high blood pressure 4 5 . For example, short sleepers with poor sleep quality had a 63% higher risk of cardiovascular disease and a 79% higher risk of coronary heart disease compared to normal sleepers with good sleep quality 5 . Additional studies have confirmed that insomnia patients are 59% more prone to coronary artery disease, 36% more prone to myocardial infarction (heart attack), and 22% more prone to stroke compared to good sleepers 6 .
If people with poor quality of sleep are at greater risk of hypertension and cardiovascular disease, is a hypertensive patient more likely to suffer from insomnia? Indeed epidemiological studies showed that insomnia and hypertension are linked: patients with hypertension are 2-3 times more likely to have insomnia than patients with normal blood pressure and also that patients with insomnia are 2-3 times more likely to have high blood pressure compared to good sleepers 7 .
It was assumed that treating daytime high blood pressure would also resolve high nighttime blood pressure. However, studies showed that ‘non-dipping’ is linked to a higher chance of developing cardiovascular disease, even in patients who take antihypertensive drugs. Such findings challenge long-held practices of treating hypertension.
How should we treat patients with hypertension and insomnia?
The emerging data led scientists and clinicians to consider bedtime ingestion of antihypertensive drugs (angiotensin-converting enzyme inhibitors or angiotensin receptor blockers) to reduce blood pressure during sleep 1 . However, this change in treatment paradigm may not be sufficient as long as problems with the biological clock and sleep that are associated with nighttime ‘non-dipping’, are not managed. Therefore, simultaneous treatment of insomnia and high blood pressure may be better suited to improve blood pressure rhythm and reduce cardiovascular risk in hypertensive patients with insomnia.