Risks and causes of chronic lymphocytic leukaemia (CLL)
Chronic lymphocytic leukaemia (CLL) is not clearly linked to any preventable causes. We don’t know what causes CLL but there are some 
that can increase your risk of developing it. These are:
- being older
- being male
- having a family history of CLL
What is a risk factor?
Anything that can increase your risk of getting a disease is called a risk factor.
Different cancers have different risk factors. Having one or more of these risk factors doesn't mean you will definitely get that cancer.
Risk factors for CLL include:
Age
Your risk of developing CLL increases as you get older. It is very rare in people younger than 40.
Sex
Men are more likely to develop CLL than women. We don't know why that is.
Family history
We know that there is some kind of genetic change in some people with CLL. But most people with CLL do not have a family history of it.
You have a higher risk of developing CLL if a close family member (parent, sibling, child) has CLL. But most people with a family history of CLL do not develop it themselves.
Where there isn't clear evidence
Some factors might increase the risk of CLL but there is not enough evidence to be sure.
Exposure to chemicals
Some studies suggest that certain hair dyes might increase the risk of developing CLL. But we need more research to clarify if hair dye use today increases the risk of CLL.
Living on a farm,or being exposed to herbicides and pesticides may be linked to an increased risk of CLL.
Other possible causes
There are often stories about potential causes in the media. It isn’t always clear which ideas are supported by evidence. There might be things you have heard of that we haven’t included here. This is because either there is no evidence about them or it is less clear.
Reducing your risk
There are ways you can reduce your risk of cancer.
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