We often hear news reports linking diabetes to a higher risk of a particular health problem. Or that certain lifestyle choices can increase or reduce your risk of developing type 2 diabetes. And often the headlines around diabetes and the risks linked with it can make for a worrying read.
- “Diabetes doubles risk of heart failure”.
- “Sleeping less than six hours triples risk of type 2 diabetes”.
- “People with diabetes three times more likely to die with Covid-19”.
But when it comes to interpreting risk, and what it really means for you, headlines like this never tell us the full story.
It’s not all relative
Risk is the possibility of something happening. And in order to understand it we need to keep in mind two common statistical ways of looking at risk – relative risk and absolute risk.
Relative risk is the likelihood of something happening in one group of people compared to another group, and this is what we usually see hitting the headlines. Scientists can calculate relative risk in order to find out if people with diabetes are more or less likely to experience an outcome compared to people without diabetes.
This can help us work out where improvements in care are needed. For example, we know people with diabetes are at greater risk of developing heart disease than people without diabetes. This is why people with diabetes have regular health checks and receive advice, support and medications to keep their risk as low as possible.
But while it can be important to look at relative risk, alone it doesn’t give us the full picture. What it doesn’t tell us is how likely we are to experience something in the first place. That’s where absolute risk comes in.
The absolute risk tells us what our risk is to begin with. If we don’t know absolute risk, relative risk is meaningless. And it’s very important to consider the size of absolute risk when thinking about relative risk. Let’s take a completely made up example.
Let’s say scientists have calculated that anyone’s absolute risk of slipping on a banana skin is 1%. In other words, taking the population of their study as a whole, 1 in every 100 people will have a slip in their lifetime.
But they find out that the likelihood for people with diabetes, compared to a group of people without diabetes, is double. This is the relative risk. It tells us that people with diabetes have an extra risk on top of the initial absolute risk. This means 2 of every 100 people with diabetes will have a banana mishap.
So while the media might choose to tell us “Diabetes doubles your risk of banana skin peril”. Another way of reporting this would be: your chance of slipping on a banana skin without diabetes is 1%, which increases to 2% if you have diabetes.
Yes, the risk for people with diabetes is higher. But, crucially, when we put it into context we see the risk for people with diabetes remains low.
And if absolute risk is very small (e.g. happens to 0.001% people), even a huge increase in relative risk for people with diabetes may not make much difference to their overall risk. Whereas if we start with a higher absolute risk (e.g. happens to 20% people), smaller increases in relative risk can have a big impact.
Risk is individual to you
Another important caveat to remember is that your risk is individual to you. When we read “people with diabetes are two times more likely to develop heart failure”, you’d be forgiven for thinking that applies directly to you. But this is the average risk for the particular group of people with diabetes in a given study.
Not everyone with type 1 or type 2 diabetes is the same. An individual’s risk will often depend on a host of other factors, like age, weight, ethnicity or where we live. Studies will usually take the main differences between people into account when calculating risks. But they can’t factor in everything unique about you that could potentially raise or lower your risk.
For example, a calculation of relative risk might overlook differences in peoples’ HbA1c, or medications they take, or how active they are. These, and many more factors, could all slightly bump up or chip away at your risk.
Diabetes is serious
Bottom line, diabetes is a serious condition that can cause real harm to physical and mental health. We have to accept that people with diabetes live with an increased risk of experiencing some health problems. But it’s so important to make full sense of that risk and keep in mind that while relative risks on the face of it may sound scary, absolute risks could remain tiny.
And our scientists are working tirelessly to make the risks people with diabetes face even lower. You can explore the research projects we’re funding and how they will lead to better care, better treatments and better lives.
