Chronic lymphocytic leukaemia is the most common type of chronic leukaemia. Read about the risk factors and causes.
How common is chronic lymphocytic leukaemia?
In total, counting all types, there are around 8,600 cases of leukaemia diagnosed in the UK each year. Around 3,500 of these are chronic lymphocytic leukaemia.
CLL is by far the most common type of chronic (slowly developing) leukaemia.
CLL is more common in people over 60 and is very rare in people under 40. Men are more likely to develop CLL than women. We don't know why that is.
Although leukaemia is the most common type of childhood cancer, leukaemia in children is nearly always acute leukaemia – either acute myeloid leukaemia or acute lymphoblastic leukaemia. Chronic leukaemia is very rare in children.
We don't know the cause of most cases of leukaemia but there are some risk factors that may increase your risk of developing chronic leukaemia.
A risk factor is something that may make you more likely to develop a particular condition or disease.
We know that there is some kind of inherited genetic change in some people who develop CLL. Studies show that people with a parent or sibling with CLL have a 6 to 9 times increased risk of developing it themselves. So far, we don't know of any specific gene changes that are linked to CLL.
CLL is most common in Australia, the USA and Europe. It is very uncommon in people from China, Japan, or Southeast Asian countries.
It is more common in white people than black people. The reasons for these differences are not known.
Other medical conditions
Results of a large European study showed that men with diabetes had double the risk of B cell chronic lymphocytic leukaemia.
Women with diabetes did not have an increased risk. We need more research to find out why this is.
Some studies have shown that people who have had certain medical conditions have a slightly increased risk of developing CLL.
The conditions include:
- pneumonia (chest infection)
- shingles infection
- auto immune haemolytic anaemia
- chronic osteoarthritis
- inflamed prostate (prostatitis)
It is possible that some of these conditions are due to reduced immunity in the early stages of CLL, rather than the cause.
One study has shown that first degree relatives of people diagnosed with Hodgkin lymphoma have double the risk of CLL. Although there is some evidence of CLL running in families, it is important to remember that most cases of CLL do not have a family link.
One study has shown a doubled risk of CLL in people who have a first degree relative diagnosed with a blood disorder called monoclonal gammopathy of undetermined significance. Having a first degree relative with lymphoplasmacytic lymphoma (also called Waldenström's macroglobulinaemia) has been shown in one study to triple the risk of CLL.
Electromagnetic fields are often talked about as a possible risk factor for developing leukaemia. We are all exposed to electromagnetic radiation.
Some research has suggested that electromagnetic fields might be a risk factor for leukaemia.
No increase in the risk has ever been found in adults who are exposed to the normal background levels people generally have in their own homes.
An overview of published evidence has shown that people with low immunity due to HIV or AIDS are three times more likely than the general population to develop leukaemia.
People treated with medicines to lower their immunity after an organ transplant have a risk that is double that of the general population.
Possible risk factors
Two studies have shown an increased risk of CLL in women who have used hair dye.
In one of these studies, they found that only women who had used permanent black hair dye had an increased risk of CLL. The other study showed an increase in risk only for women who used hair dyes before 1980. We need more research to clarify if hair dye use today increases the risk of CLL.
Research has looked at being overweight and your risk of CLL. One study that combined the results of four previous studies showed that people who are very overweight (obese) have a slightly increased risk of CLL. But we need more research to be sure that being overweight really does increase the risk of CLL.
Radiation is known to increase the risk of other types of leukaemia but has not generally been linked to an increased risk of CLL.
There is one study that showed an increased risk of CLL in Czech uranium miners who had high exposure to radon (a radioactive gas).