Urbanisation and incidence of acute lymphocytic leukaemia among United States children aged 0–4

Abstract

Acute lymphocytic leukaemia (ALL) incidence among children under 5 years of age was examined, utilising data from 24 United States cancer registries. County-based incidence rates among white children were compared across four levels of urbanisation: large and small metropolitan counties, and adjacent and nonadjacent rural counties. In metropolitan areas, the incidence of ALL was lower among blacks (rate ratio (RR) ¼ 0.38, confidence interval (CI) ¼ 0.33 -0.44) and among Asians/Pacific Islanders (RR ¼ 0.78, CI ¼ 0.63 -0.97) than among whites. Among white children, the incidence of ALL decreased across the four strata of urbanisation, from 67 to 62 to 65 to 54 cases per million person-years at-risk (two-sided trend P ¼ 0.009), such that rates were significantly lower in the most remote rural counties than in the most populous metropolitan counties (RR ¼ 0.80, 95% CI ¼ 0.70 -0.91).

Population mixing, socioeconomic status and incidence of childhood acute lymphoblastic leukaemia in England and Wales: analysis by census ward

“…Previous studies in Britain have also found a higher incidence of ALL in rural or isolated areas (Alexander et al, 1990b;Dickinson and Parker, 1999). This contrasts with findings of higher incidence in urban areas in several other countries, including Greece (Petridou et al, 1997), Taiwan (Li et al, 1998), Sweden (Hjalmars et al, 1999) and the United States (Adelman et al, 2005). None of these studies controlled for socioeconomic status, however, and patterns of socioeconomic status in relation to urbanisation may differ between countries.…”

Residential mobility and risk of childhood acute lymphoblastic leukaemia: an ecological study

“…The lower incidence among blacks is well known (Greenberg and Shuster, 1985;Parkin et al, 1988;Rechavi et al, 1992;Smith et al, 1998Smith et al, , 1999Adelman et al, 2005) and is conceivably due in part to socioeconomic disparities within the US. However, our data set cannot test this possibility and the ratio between the highest and lowest rates of the quartiles for income X$5000 (an SES measure) was not large enough to account for race completely.…”

“…Except for our previous finding of a rural-urban gradient among white males (but not females) (Adelman et al, 2005), few published studies have examined the role of sex directly in conjunction with other risk factors for childhood ALL, as we have done, in part because most studies of risk factors for ALL have either matched on or adjusted for sex. One previous study examining birth weight as a risk factor found that both birth weight over 3000 g and male gender were risk factors for childhood ALL in a multivariate model (Paltiel et al, 2004).…”

“…UK studies (Alexander et al, 1990b(Alexander et al, , 1996Gilman and Knox, 1998;Dickinson and Parker, 1999) have found higher rates of childhood ALL or non-Hodgkin's lymphoma (NHL) in rural areas. However, studies elsewhere (McWhirter and Bacon, 1980;Muirhead, 1995;Petridou et al, 1997;Li et al, 1998;Hjalmars and Gustafsson, 1999;Adelman et al, 2005) have found higher ALL incidences in urban or highdensity regions.…”

“…The nonmetropolitan counties were divided into subgroups based on adjacency to metropolitan areas as well as percentage of population residing in urban areas. For comparability to a study published previously (Adelman et al, 2005) and to obtain reasonably precise point estimates of incidence rates, we opted to emphasise the proximity of nonmetropolitan counties to metropolitan areas while collapsing the subcategories of urban population among the nonmetropolitan counties. Counties in this study were grouped into four strata in order of decreasing urbanisation: metropolitan counties with population X1 000 000 (codes 0 and 1), metropolitan counties with population o1 000 000 (codes 2 and 3), nonmetropolitan counties, adjacent to a metropolitan area (codes 4, 6, and 8), and nonmetropolitan counties, not adjacent to a metropolitan area (codes 5, 7, and 9).…”