About the research
Many cancers are more prevalent among lower socio-economic communities; this could possibly be due to higher rates of exposure to cigarette smoke and environmental carcinogens. But there could be a reverse association in the case of childhood leukaemia. Record-based studies have indicated that childhood leukaemia is more prevalent among the affluent, but recent findings have been less consistent. This research aimed to quantify this association for England and Wales, and assess any change over time.
The findings suggest that there was a persistent socio-economic gradient in recorded childhood leukaemia incidence in England and Wales. In three successive decades, the leukaemia rate among the poorest fifth of children was approximately 90 per cent of the rate among the most affluent. Possible explanations for the socio-economic gradient include associations with unusual patterns of exposure to infection, and other hypothesised risk factors related to relatively affluent lifestyles. However, a further study using clinical data suggests that under-diagnosis of leukaemia in children from poorer communities may be a contributing factor.
This finding has potential implications for studies aimed at understand the underlying causes for this association, and perhaps also for clinical practice in Britain and elsewhere.
Methodology
Records from the National Registry of Childhood Tumours (N=11940) were grouped by year of diagnosis in decades centred on census years 1981, 1991 and 2001. The socio-economic status of each case was measured by the Carstairs deprivation index of the census ward that contained the postcode of the address at diagnosis, using the ward boundaries and Carstairs index from the appropriate census. Childhood leukaemia rate ratios, in fifths of socioeconomic status relative to the most deprived, were estimated by Poisson regression for each decade and overall. The Census Dissemination Unit (now part of the UK Data Service) provided the Geoconvert system for allocating postcodes to census wards, Casweb (for accessing age-specific census populations by ward), and the 1991 Carstairs deprivation index.
Publications
Kroll, M. E., Stiller, C.A., Murphy, M.F.G., and Carpenter, L.M. (2012) ‘Childhood leukaemia and socioeconomic status in England and Wales 1976-2005: evidence of higher incidence in relatively affluent communities persists over time’, British Journal of Cancer, 105(11), pp. 1783-1787. doi:10.1038/bjc.2011.415 Retrieved 28 August 2013 from http://www.nature.com/bjc/journal/v105/n11/full/bjc2011415a.html
Kroll, M.E., Stiller, C.A., Richards, S., Mitchell, C., and Carpenter, L.M. (2012) ‘Evidence for under-diagnosis of childhood acute lymphoblastic leukaemia in poorer communities within Great Britain’, British Journal of Cancer 106(9), pp. 1556-1559, doi:10.1038/bjc.2012.102 Retrieved 28 August 2013 from http://www.nature.com/bjc/journal/v106/n9/full/bjc2012102a.html
Further information see the Childhood Cancer Research Group website.