High blood pressure

We seek to understand the relationship between blood pressure and the brain, and in particular, how managing blood pressure can improve cognitive health.

Blood pressure is the amount of force that is exerted on the arterial walls by blood as it is pumped around the body by the heart. High blood pressure, also known as hypertension, occurs when blood is pumping with more force than normal through arteries.

High blood pressure is common, affecting around one in seven Australians. This figure increases in older Australians, who may experience an increase in blood pressure due to their arteries becoming more rigid (less elastic).

Blood pressure is very variable and can be elevated transiently by stress, emotional state, recent physical activity, smoking, caffeine and even talking. A diagnosis of hypertension is only given if a blood pressure reading from an instrument called a sphygmomanometer is higher than 140/90 mmHg after several visits to a GP. If the first figure is higher than 140, or the second figure is higher than 90, this is considered to be an indicator of high blood pressure. It is recommended that you measure your own blood pressure with an automatic blood pressure monitor first thing in the morning, while you are still in bed; blood pressure monitors can be purchased at most chemists.

Contributing factors

Some drugs and an unhealthy lifestyle can also result in hypertension. It is important to have your blood pressure checked regularly (preferably yearly) by your GP as there are no symptoms for hypertension and it can be a risk factor in many diseases such as heart attack, kidney failure or stroke.

Lifestyle changes to improve blood pressure include increasing cardiovascular fitness by undertaking regular physical activity, cessation of smoking, a reduction in alcohol intake, and reducing fat and salt in the diet. Nevertheless, if blood pressure remains high than antihypertensive medications are required to maintain your blood pressure in a healthy range. Your GP will need to monitor your blood pressure regularly because if the dose of your antihypertensive medication is too high your blood pressure will fall, leading to dizziness and fainting on standing.

Our research approaches

Our research interest in this area is the role of the brain in controlling blood pressure. By inserting a fine needle (microelectrode) into a peripheral nerve we can record the spontaneous bursts of muscle sympathetic nerve activity (MSNA) that originate in the brain and cause constriction of blood vessels in muscle. High levels of MSNA can lead to hypertension. By recording MSNA at the same time as performing fMRI of the brain we can identify sites in the brain responsible for generation of MSNA.

Using this same approach, we have studied patients with renovascular hypertension, before and after treatment with renal angioplasty. The goal of this is to increase our understanding of how sensory signals from the kidneys to the brain can lead to high blood pressure.

Our research discoveries

In a previous NHMRC-funded grant we showed that certain areas of the brain coupled to the production of MSNA increased their activity in people with Obstructive Sleep Apnoea (OSA), in which MSNA and blood pressure are greatly elevated. These changes were reversed following six months of Continuous Positive Airway Pressure (CPAP).

We have also previously explored how high blood pressure and cholesterol affect the risk of developing cognitive decline or dementia, and found that high blood pressure in midlife is a risk factor for cognitive decline and dementia. Historically, high blood pressure, cholesterol and dementia have all been treated as separate medical issues but our research brought a holistic perspective.