Risks and causes of chronic lymphocytic leukaemia (CLL)

Your risk of developing cancer depends on many factors. This includes things like whether you smoke and have a healthy balanced diet, as well as genetic and environmental factors. 

Anything that can increase or decrease your risk of cancer is called a risk factor. 

We don't know what causes most cases of chronic lymphocytic leukaemia (CLL). But there are some factors that may increase your risk of developing it.  

Having one or more risk factors doesn't mean that you will definitely get leukaemia. 

Risk factors for CLL include:


Your risk of developing CLL increases as you get older.  It is very rare in people younger than 40.


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 inherited 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.

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    B Eichorst and others.
    Annals of Oncology, 2021, Volume 32 Issue 1 pages 22-33

  • Elevated risk of chronic lymphocytic leukemia and other indolent non-Hodgkin's lymphomas among relatives of patients with chronic lymphocytic leukemia
    LR Goldin and others
    Haematologica, 2009, Volume 94, pages 647-53

  • Familial predisposition and genetic risk factors for lymphoma. 
    JR Cerhan and SL Slager
    Blood 2015, Volume 26, pages 2265–73 

  • Personal use of hair dyes and risk of leukemia: a systematic literature review and meta‐analysis
    K Towle and others
    Cancer Med. 2017, Volume 6, issue10, pages 2471–2486.

  • Medical History, Lifestyle, Family History, and Occupational Risk Factors for Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma: The InterLymph Non-Hodgkin Lymphoma Subtypes Project
    S Slager and others
    J Natl Cancer Inst Monogr. 2014 Volume 48, pages 41–51.

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. If you need additional references for this information please contact patientinformation@cancer.org.uk with details of the particular issue you are interested in.

Last reviewed: 
17 Sep 2021
Next review due: 
17 Sep 2024

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