Hypertension – High Blood Pressure
Hypertension – high blood pressure – is a ‘silent’ killer, and a problem that is common in the general population, but even more common in people with diabetes. As many as one in five New Zealanders may have high blood pressure, and up to half of people with diabetes are estimated to have high blood pressure.
What is “Blood Pressure”?
The term ‘Blood Pressure’ relates to the pressure in the arteries, which are the main blood vessels taking blood away from the heart to the rest of the body.
Heart muscle contracts and pumps blood around the body in a rhythmic fashion that we know as the ‘heart beat’. When the heart beats, blood is forced through the arteries and the pressure rises to a maximum, called the systolic pressure. In between each heart beat the pressure falls to a minimum, called the diastolic pressure.
Pressures are measured in millimeters of mercury (mmHG), but we express blood pressure verbally as the systolic pressure “over” the diastolic pressure. For example, a blood pressure of “one twenty over seventy” would be written as 120/70 and refers to a systolic pressure of 120 mmHg and a diastolic pressure of 70 mmHg.
How is BP Measured?
Blood pressure is usually measured in the upper part of the arm with the aid of a sphygmomanometer (sfig-mo-manometer what a mouthful!). This consists of an inflatable cuff, a measuring unit (the ‘manometer’ bit), a tube that connects these, and, in older models that do not inflate automatically, a bulb that the health professional uses to inflate the cuff. The cuff is usually placed around the upper left arm, at roughly the same vertical height as the heart. A stethoscope is placed on the inside of the elbow, where a pulse can be felt and the health professional listens to the sounds of the blood in the artery as the heart pumps…
The cuff is inflated until the pressure temporarily stops blood flow. Listening with the stethoscope to the brachial artery at the elbow, the health professional slowly releases the pressure in the cuff. As the pressure in the cuffs falls, a “whooshing” or pounding sound is heard (see Korotkoff sounds) when bloodflow first starts again in the artery. The pressure at which this sound is heard is recorded as the systolic pressure. The pressure is then slowly reduced until the sound can no longer be heard; this is recorded as the diastolic pressure.
Automated machines are now more commonly used to measure blood pressure, and from this technology a new era of home BP monitoring is evolving.
What is an Acceptable BP?
Hypertension is usually defined as a BP above 140/90 mmHg – however having diabetes complicates matters…
Target levels for blood pressure in people with diabetes are currently being debated. The threshold value above which treatment for hypertension should be started is lower than in people who do not have diabetes. This is because of the additive effects of diabetes and high blood pressure (see below).
Most of the treatment benefit occurs if blood pressure can be reduced to lower than 130/70 mmHg and the American Diabetes Association suggest that this is “reasonable if it can be safely achieved” (1). New Zealand guidelines are in support of this target (2).
Blood Pressure Numbers
Hypertension is generally defined as:
Target for people with diabetes:
Note: Your specific BP target may be lower than this, depending on the presence of complications, especially kidney disease.
Home BP Monitoring
There are a number of home blood pressure monitors currently available in New Zealand. Cheaper models may be less reliable, but this is not always the case. It’s a good idea to double check your monitor against one at the doctor’s surgery – ask your nurse – this will help to make sure that you are using the monitor correctly, and verify that it is giving you accurate results.
Ambulatory (24-hour) Blood Pressure Monitoring
White Coat Hypertension
Sometimes the stress of visiting the doctor or hospital can significantly increase your blood pressure; this is termed ‘white coat’ hypertension (I have also seen it referred to as ‘isolated office’ hypertension). In such cases, a true, accurate blood pressure reading may only be obtained in the home environment, and home blood pressure monitoring may be recommended (see above).
The possibility that people who suffer from white coat hypertension may be at an increased risk of complications resulting from high blood pressure is still being debated.
Relationships between Hypertension, Diabetes, and Complications
In Type 2 diabetes, high blood pressure is often present as part of the ‘metabolic syndrome’ of insulin resistance (which also includes apple shaped obesity and disordered levels of blood fats… See ‘What is Diabetes‘ for more on this).
In Type 1 diabetes, high blood pressure may reflect the onset of nephropathy – diabetic kidney disease.
Having hypertension increases the risk of developing macrovscular disease – heart disease and circulatory problems in the legs and feet (the latter is often termed ‘peripheral vascular disease‘ or ‘peripheral arterial disease’ (PAD)).
It is commonly cited that high blood pressure is associated with heart disease, however adding diabetes into the equation may double the risk: People with both diabetes and hypertension may have double the risk of heart disease, compared with nondiabetic people with hypertension.
THE IMPORTANCE OF BLOOD PRESSURE
The UKPDS, a landmark study carried out in the UK over 20 years, demonstrated that in people with Type 2 diabetes, controlling blood pressure is just as important as controlling blood glucose levels when it comes to developing complications of diabetes(3).
What causes High Blood Pressure?
How does High Blood Pressure cause so much damage?
High pressure in the arteries damages the lining of the blood vessels and accelerates the development of atheroma, leading to ‘hardening of the arteries‘.
*Note: Relationships between high blood pressure and diabetes-related nerve damage have not yet been demonstrated and reported in the medical and scientific literature to such an extent as to provide a good evidence base for sweeping or generalised statements.
Treating Hypertension in Diabetes
The essential dietary factor, when it comes to blood pressure, is salt – essentially sodium. An acceptable low sodium intake is less than 2g (2000mg) per day. Many processed foods are high in salt, as are crisps, salted peanuts, other savoury snacks and biscuits, and canned and smoked foods – consumption of these should be reduced. Use Lite salt, and try alternatives such as herbs and spices to enhance flavour in cooking. (More dietary and recipe advice is available from Diabetes New Zealand.)
Weight loss can also help to improve blood pressure, independent of sodium intake, and this will help with blood glucose control and blood lipid (fat) levels too.
Moderation of alcohol intake (maximum of 1 or 2 drinks daily) is also recommended.
The DASH (Dietary Approaches to Stop Hypertension) eating plan is frequently referred to in the literature. This is an eating style, rather than a specific diet, or weight-loss plan, which has been well-researched and proven to reduce high blood pressure.
DASH lays the emphasis on eating the following types of foods:
…with some of the following:
… and only occasional servings of:
The beneficial effects of exercise are frequently overlooked when it comes to prescribing treatments for hypertension.
Moderate-intense physical activity for 30 minutes every day is recommended for good health and fitness. For people aged over 35 years, stress-testing may be advisable before starting a vigorous exercise program, depending on general level of fitness.
Walking is always a good place to start; try investing in a pedometer, and build up the daily exercise gradually.
Note: Footwear is important when exercising; see section on footwear in ‘Legs and Feet‘.
Stress is now well recognised as a significant factor associated with hypertension. So, in addition to other lifestyle changes (diet and exercise), you may need to find ways of better coping with stress in your daily life.
There are two things to consider when it comes to day-to-day stress management:
- Sources of stress – work, family life, and so on
- Ways of dealing with stress – coping and relaxation methods
Take a look at the page ‘Coping with Stress‘ in the Healthy Living section of this website.
Drug treatment of hypertension has been shown in clinical trials to reduce both macrovascular (notably heart disease) and microvascular complications of diabetes (notably retinopathy and nephropathy).
There are a number of different types of drugs that are used to lower blood pressure (see table). The general rule is to keep adding medication in order to keep blood pressure levels down – so you may end up on a number of different drugs, all “for blood pressure”.
Summary Table of Antihypertensive Agents
|Name and Type
|How the drug works
|Angiotensin-converting enzyme (ACE) inhibitors
Generic names end in “-pril” e.g. captopril, lisinopril
The drugs of first choice are usually ACE Inhibitors; there are a number of these and some appear to be better suited to some people than others, so sometimes you may try one or two before finding one that suits you.
Second choice are usually ARBs – these are angiotensin receptor blockers
Explore this section: Long Term Complications