Health & beauty

Health numbers

Updated: 03 Dec 2008
Health-numbers-hero

Introduction

Many numbers are used to measure your health. We explain the top 5, and what to aim for as a healthy adult.

From blood pressure to cholesterol to BMI, our health is often described by numbers. You need to know what the numbers mean: what's normal, what's optimal, what's to be avoided, and most importantly how to stop them from going bad.

Knowing your health numbers - and whether they need to go up or down - could save your life.

Blood pressure

Blood pressure

Blood pressure is the force of the blood pushing against the walls of your arteries as it moves around your body. It's always given as two numbers.

The top number - systolic pressure - indicates the pressure in the arteries when the heart beats and pumps blood.

The bottom number - diastolic pressure - represents the pressure as the heart relaxes between beats. If your systolic pressure is greater than 140 or your diastolic pressure is greater than 95 on several tests you have high blood pressure.

Untreated, high blood pressure can lead to serious problems such as heart attack, stroke and kidney disease. It's sometimes called the silent killer because it usually has no warning signs - you can have high blood pressure and feel perfectly well. The only way to find out if you have high blood pressure is to have it checked.

Risk factors

Smoking, physical inactivity, being overweight or obese, poor nutrition and excessive alcohol consumption can all increase your risk of high blood pressure.

The numbers:

  • Aim for: Less than 130/80mmHg. Lower is usually better, although very low blood pressure can sometimes be a cause for concern and should be checked by a doctor.

  • Check it: Every 2 years from age 18 if it's normal. More frequently if you have a personal or family history of high blood pressure ("hypertension"), stroke or heart attack.

Jargon buster

mm/Hg: millimetres of mercury - the height of a column of mercury that's supported by the pressure created by the heart pumping blood through the arteries.

Cholesterol

Cholestrol

Cholesterol is a lipid (a fat-like substance) that occurs naturally in the body. It's essential to help you function properly, but your body generally makes all it needs.

Cholesterol is transported in the blood by carriers called lipoproteins. There are two main types: low-density lipoprotein (LDL) is usually referred to as "bad" cholesterol because it can clog up your arteries; high-density lipoprotein (HDL) is known as "good" cholesterol because it helps take cholesterol out of the bloodstream.

Triglycerides form much of the fat stored by our body. High triglyceride levels have been linked to many diseases including heart disease and stroke.

High cholesterol doesn't produce any symptoms and many people first learn they have it only when they have a heart attack or stroke. Certain lipid rates are also risk factors for other conditions (see "Blood glucose"), so it's useful to know your numbers.

You'll usually be asked not to eat for 9 to 12 hours before your test - so that your food has had time to be digested and won't affect the results. The lipid profile from a blood test after fasting gives a breakdown of total cholesterol, LDL, HDL and triglycerides, and the ratio which is used to check your risk. A finger-prick cholesterol test (such as what's offered by some pharmacies) gives you total cholesterol only.

Risk factors

Eating too much saturated fat leads to excessive cholesterol in your blood, which can increase your risk of heart disease and stroke. Being overweight and excessive alcohol drinking are also risk factors.

The numbers:

Aim for:

  • Total cholesterol (TC) below 4 mmol/L
  • LDL below 2.0 mmol/L
  • HDL above 1 mmol/L
  • TC/HDL ratio below 4.0
  • Triglycerides below 1.7 mmol/L.

Any lowering of total and LDL levels and any raising of HDL cholesterol can be beneficial even if you're not reaching the targets.

  • Check it: Every 5 years from age 45 for men, 55 for women (but from 10 years younger if you're in a high-risk group). It requires a blood test.

Jargon buster

mmol/L: millimoles per litre - a measure of concentration using molecular count.

Blood glucose

Blood glucose

The level of glucose (sugar) in your blood is controlled by insulin, and when your body can't use or make enough insulin this can result in low blood glucose (hypoglycaemia) or high blood glucose (hyperglycaemia).

Chronic hypoglycaemia can lead to brain and nerve damage. Chronic hyperglycaemia indicates diabetes - which if left untreated can cause progressive damage to body organs such as the kidneys, eyes, heart, blood vessels, and nerves and can increase your risk of heart attack or stroke.

A blood glucose test after fasting can determine if your blood glucose level is within a healthy range.

If your fasting blood glucose is greater than 7mmol/L on two tests you have diabetes.

If it's between 6.1 and 6.9mmol/L you may have a condition called pre-diabetes or impaired-fasting glycaemia. Pre-diabetes is a stage when blood glucose levels are higher than normal but not high enough for a diagnosis of type 2 diabetes.

If you have pre-diabetes you can and should do something about it. Studies have shown that changes to your lifestyle - moderate weight loss and regular exercise - can prevent or delay the onset of type 2 diabetes.

Risk factors

You are at risk for diabetes if you are overweight and aged 40 or older, or 30 years or older if you're of Maori, Pacific, Middle Eastern or Asian descent. Other risk factors include high blood pressure, low HDL cholesterol and high triglycerides, a family history of diabetes or giving birth to a baby weighing more than 4 kg.

The numbers:

  • Aim for: 3.0 to 5.4 mmol/L. Important: these numbers are intended for screening healthy individuals. They are not appropriate target levels for people with diabetes.

  • Check it: Every 3 years from age 55. Start younger and check more frequently if you have a high risk of type 2 diabetes.

Jargon buster

mmol/L: millimoles per litre - a measure of concentration using molecular count.

Waist circumference and BMI

Waist circumference

Waist circumference

Waist circumference is a measure of abdominal fat. Having fat around your abdomen ("apple" shape), regardless of your body size, has been linked to an increased risk of diseases such as heart disease and type 2 diabetes. Fat predominantly deposited around the hips and buttocks ("pear" shape) doesn't appear to carry the same risk.

The numbers:

  • Aim for: A waist circumference of less than 100cm (men) or 90cm (women).

  • Check it: As often as you like - all you need is a tape measure. Measure your waist at its narrowest point while standing up with your stomach relaxed.


Body mass index

Body mass index (BMI)

Body mass index (BMI) is a measure of your weight adjusted for height. It gives an approximate measure of your total body fat and indicates whether you're overweight or obese. If you are, you're at risk of developing other conditions such as diabetes, heart disease, high blood pressure, osteoarthritis and some cancers.

The numbers:

  • Aim for: 18.5 to 24.9. Less than 18.5 is underweight, 25 to 30 is overweight, higher than 30 is considered obese.

  • Check it: Divide your weight (in kilograms) by your height (in metres) squared. A person who weighs 60kg and is 1.65m tall, for example, has a BMI of 22 (60 divided by [1.65 x 1.65]). This is in the normal range.

Some cautions: The BMI does not distinguish between weight associated with fat and weight associated with muscle so it has its limitations.

  • It may over-estimate body fat in pregnant women, athletes and others who have a muscular build. Conversely, it may under-estimate body fat in the elderly and others who have lost muscle mass.

  • It can be misleading in children as body fat changes as they grow. Boys and girls also differ in their body fat as they grow.

Stop your numbers going bad

Lifestyle can have a huge impact on your numbers. You've heard it all before ... but health professionals think these messages are worth repeating:

Stop smoking + Eat nutritious food + Exercise regularly + Drink in moderation.

  • If you're a smoker get help to stop.
     
  • Eat a wide variety of nutritious foods - plenty of plant- and cereal-based foods with some lean meat, fish, poultry, dairy or alternatives; limit your saturated fat intake; consume only moderate amounts of total fats and sugars; choose food low in salt; drink plenty of water.
     
  • Exercise regularly. Aim to do at least 30 minutes of moderately intense activity on most days of the week.
     
  • If you drink alcohol, do so in moderation.
     
  • If you're a man over 45, or a woman over 55, ask your GP or practice nurse for a heart health check.

National health numbers

In the 2006/2007 New Zealand Health Survey:

  • One in 7 adults (13.6 percent) were taking medication for high blood pressure.
  • One in 12 adults (8.4 percent) were taking medication to lower their cholesterol levels.
  • One in 3 adults (36.1 percent) of adults were overweight and a further 1 in 4 (26.5 percent) were obese.
  • One in 20 adults (5 percent) had doctor-diagnosed diabetes. Almost all had type 2 diabetes.

 

More information

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