Why do I need evidence-based medicine?

In this section
Key points about evidence-based medicine
Why evidence from research is so important
How to weigh up other sorts of evidence

In the past, doctors didn’t always have access to the latest medical research. They often used to decide how to treat patients using only their own judgement and experience, and what they learnt at medical school. We now know that this is not the best way to practise medicine. This is because what doctors think is best for a patient is not always what is best when you actually look at the research.

When researchers study a disease or a condition, they look at many more patients than a doctor will ever treat. Also, medical knowledge changes all the time. And what doctors used to think was the best thing to do, even a few years ago, might actually be considered harmful today.

Only by looking at all the evidence and judging it fairly can you work out what the research really says about a treatment. This is called practising evidence-based medicine.¹

Best Health is based on information from Clinical Evidence, a publication for doctors written by experts from all over the world. These experts look at all the evidence for a treatment. They weigh it up carefully and decide which treatments work and which don't work. They include research studies that have been published and those that haven't been published.

Key points about evidence-based medicine

• All evidence is not alike. Some evidence is better than other evidence.
• When doctors look at the research before recommending a treatment, they are using evidence-based medicine.
• Evidence-based medicine looks at all the research that there is about a disease or treatment.
• When researchers look at whether a treatment works, they look at many more patients than your doctor will ever treat.
• Sometimes the evidence can't tell you which treatment is best for you, so it's important that you weigh up the benefits and harms of treatment carefully.

Why evidence from research is so important

All evidence is not alike. It can be dangerous to rely on what your neighbours or friends tell you. For example, just because a cancer drug worked for them, that does not mean it will work for you. Also, there have been many ways of doing things in medicine that were later found to be useless or even harmful when studies were done.

Here are some examples:

• Fifty years ago, women were often given an enema while they were in labour. This is uncomfortable and unpleasant. But doctors thought that enemas would reduce the risk of infection for the woman and her baby. Some hospitals gave soapy enemas, which were painful for women. When doctors studied the results from the research, they found there was no evidence that enemas prevented infections. Two studies showed that enemas made more of a mess, and women felt embarrassed by the enema.² Women no longer have enemas while they're in labour.
• Resting in bed used to be recommended for many conditions. But now we know that it can often do more harm than good. People who have had a heart attack, for example, do better both physically and mentally if they begin exercising as soon as they feel well enough.
• Many children used to have their tonsils removed to stop them from getting throat infections. The operation is rare now, because the risk of complications from surgery makes it likely to do more harm than good.

Sometimes research has proved that a treatment works, but doctors have been slow to start using the treatment. For instance, tens of thousands of premature babies died because a treatment that could help them breathe better was not widely used. In 1972, the first of several studies was published showing that giving drugs (called corticosteroids) to women about to have a premature baby could help the baby's breathing.³ But it was another 20 years before obstetricians (doctors who specialise in pregnancy and childbirth) began using these drugs regularly.

How to weigh up other sorts of evidence

What friends and family say

When you aren't well, your family and friends often give you advice and tell you about their experiences. These stories can be very powerful. If your mother says that your daughter has had so many sore throats that she needs to have her tonsils taken out, you may believe what she says because she is your mum. She may say that when you had your tonsils out you stopped missing school and started eating better and growing more.

But many thousands of children have their tonsils out each year, and there is no evidence from research studies that it does them any good at all. Some even get complications from the surgery, such as bleeding. Your mum means well, but one person's story is just that. It is the story of one person who had a treatment. It is not the story of thousands of others who have also had it.

For example, you often hear stories of people who have survived cancer because they went on strict diets. However, you are less likely to hear about people who went on strict diets and died. They are not around to tell their stories. It can be hard to follow a strict diet if you have cancer and find it hard to eat. It may keep you from enjoying your life. You should think carefully before you start a diet that is difficult and unpleasant to follow, and do it only if you will get some real benefits from it.

But you can learn a lot from one person's experience of treatment. Research studies do not always look at the things that matter to you. What friends and neighbours and other people with your condition say is important. But you shouldn't use this information on its own when you make decisions about treatment.

What your doctor says

It's tough for busy health professionals to keep up to date with advances in medical knowledge. A doctor would have to read 17 articles in medical journals every day of the year to keep up with new information in his or her area of medicine.⁴

More medical information is now summarised to make it easier for doctors to keep up to date. But not all doctors use this type of information. That means there is a big difference in how conditions are treated across the country.⁵

Sometimes there is more than one treatment for a condition. This is why what you want out of your treatment and your life are so important when deciding which one to have.

For example, if men have prostate cancer the choice of treatments is complicated. Some doctors recommend surgery, others recommend radiotherapy and some think men will do just as well without any treatment.⁶

When there is no right answer, you need to make sure you understand the risks and benefits of the treatments being offered to you.

What the experts say

Your doctor may be an expert in his or her field. Oryour doctor may decide how to treat you based on what other experts in the field say. Much of what doctors learn at medical school is based on what experts think. Doctors like to ask their colleagues for advice.

But experts don't always get it right. It is safer to rely on the results of good research studies than on one person's opinion, no matter how well known they are.

A few decades ago, medical experts said that all pregnant women should have X-rays to measure the bones in their pelvis. Doctors wanted to do this to make sure the babies had enough room to get out. We now know this does more harm than good. It is not good to give X-rays, which are done using radiation, to an unborn baby.

What the media say

Every day there are stories in newspapers or on television about the latest discoveries in health care. One day you may hear that drinking alcohol stops you getting heart disease. The next day you may hear that it can increase the risk of getting breast cancer. What should you do?

There are also a lot of sites on the internet that provide health information. But it can be hard to know which ones to trust.

The media often report on the results of just one study. There may have been other studies that had different results, and the reporter may not know about these. Usually, any one study just adds a brick into a growing wall of evidence. The results of one study cannot tell you the whole story. It is only after other groups of researchers repeat the study and find the same results that answers become reliable.

You do not need to make a decision on the basis of one study

The media also tend to be optimistic about advances in medicine. A study that looked at how the media reported on drug treatment for osteoporosis and high cholesterol found that the benefits were stressed but the problems the drugs could cause were barely mentioned.

What tradition says

Just because something has been used for years doesn't mean it works or can't hurt you. Many complementary and alternative medicines (such as herbal products or vitamins) have been used for years. But there isn't always good evidence that they do more good than harm.

One study looked at seven reference books.⁷ It found that more than 100 different complementary medicines were recommended for asthma. But there was no good evidence that they worked.

Traditional remedies may have been used for centuries, but they may not be safe when taken with modern medicines. St. John's wort, for example, is a herbal remedy for depression. Unfortunately, it stops some other drugs, such as the contraceptive pill and blood-thinning tablets, from working properly.

Questions to ask your doctor

Here are some questions that might help you weigh up the information you find in the media or on the Internet about treatments. You could show these questions to your doctor.

• How could this treatment help me? Has it been studied in people like me?
• Is it likely that this drug will harm me? Am I more likely to get side effects than other people? (For example, older people sometimes have more side effects.)
• Who is telling me about this treatment? Is there a reason they want to tell me how good it is? (Sometimes doctors are paid by companies to say good things about their drugs and products.)
• How strong is the evidence that this treatment works? Are the results of a study published in a medical journal? Is just one person telling their story on television?
• What are the alternatives to the treatment being offered?
• What are the costs of the treatment? (These can include such things as inconvenience, not just financial costs.)