Study: Childhood leukemia and socioeconomic status

Children in Canada's poorest neighbourhoods are somewhat less likely to get leukemia than those in the richest neighbourhoods, according to a new study of childhood leukemia patterns by neighbourhood income.

This study, which has been published in the July 2005 edition of the journal Epidemiology, was based on data from Canada's 10 provincial cancer registries, analysed by researchers from the British Columbia Cancer Agency, Statistics Canada and the Electric Power Research Institute.

It found a slightly lower relative risk of childhood leukemia in the poorest one-fifth of neighbourhoods, compared to the richest one-fifth.

The lower risk in the lowest income neighbourhoods was mainly restricted to acute lymphoid leukemia. This effect was slightly stronger in urban areas.

According to other studies cited, one possible explanation could be early contact with infectious agents and consequent development of antibodies which are thought to confer some protection against the development of leukemia. This contact might be more prevalent in neighbourhoods with lower income and poorer living conditions.

Leukemia is one of the most common potentially fatal illnesses in Canadian children. For the most part, its causes are not well understood.

This study was undertaken to determine whether there is a difference in incidence of childhood leukemia for different levels of socioeconomic status, measured by neighbourhood income.

All cases of invasive childhood leukemia, that is, in children up to the age of 19, diagnosed between 1985 and 2001 were identified from the 10 provincial cancer registries in Canada. Postal codes for the place of residence at the time of diagnosis were used to assign cases to census neighbourhoods.

Quintiles of population by neighbourhood income, as well as the population at risk by sex and five-year age groupings, were constructed from census population data using the census year closest to the year of diagnosis.

Definitions, data sources and methods: survey number 3207.

The study "Childhood leukemia and socioeconomic status in Canada," was published in Epidemiology 2005 July; 16(4): 526-531. An abstract of the article is available free online (http://www.ncbi.nlm.nih.gov/entrez) in English only.

For more information about the concepts, methods or data quality of the study, or to obtain a copy, contact Russell Wilkins (613-951-5305; russell.wilkins@statcan.gc.ca), Health Analysis and Measurement Group, or Marilyn Borugian (604-675-8058; mborugia@bccancer.bc.ca), Cancer Control Research, British Columbia Cancer Agency.