Evidence of population mixing based on the geographical distribution of childhood leukemia in Ohio.
BACKGROUND
This ecologic study examined the geographic distribution of childhood leukemias in Ohio, 1996-2000, among children aged 0-19 for evidence that population mixing may be a factor.


METHODS
(1) State incidence rates were compared to Surveillance, Epidemiology and End Results (SEER) rates for each year and for the 5-year period, 1996-2000; (2) incidence rates for each of Ohio's 88 counties were compared to statewide rates; and (3) county incidence rates were compared based on population density, population growth, and rural/urban locale. SEER*Stat version 5.0 was used to derive age-specific and 0-19 age-adjusted rates. Expected values, standardized incidence ratios (SIRs), and Poisson P-values were calculated with Excel using the indirect method of standardization.


RESULTS
Of the 585 cases, 73.3% were acute lymphocytic leukemia (ALL), 16.6% acute myelogenous leukemia (AML), 3.2% acute monocytic leukemia (AMoL), and 2.6% chronic myelogenous leukemia (CML). Rates for total leukemia burden were significantly below national levels for all races (P = 0.00001), likely due to poor ascertainment of cases. Yearly incidence rates for 1996-2000 were stable for ALL and AML; CML rates declined over the period. Based on 2000 Census and intercensal population estimates for 1996-2000, statistically higher rates for ALL were noted for counties experiencing >10% population change 1990-2000 (P < 0.05), especially for ages 1-4 (P < 0.03) in counties with 10-20% growth. Counties 67.9-99.2% urban experienced fewer than expected cases of AML + AMoL (P < 0.06).


CONCLUSIONS
Data support Kinlen's theory of population mixing and warrant further studies in Ohio, the US and other countries.
Clark
Brenda R
BR
Division of Health Behavior and Health Promotion, School of Public Health, The Ohio State University, Ohio 43210, USA. bclark@sph.osu.edu
Ferketich
Amy K
AK
Fisher
James L
JL
Ruymann
Frederick B
FB
Harris
Randall E
RE
Wilkins
John R
JR
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000453:epidemiology*; D015470:Leukemia, Myeloid, Acute / Q000453:epidemiology*; D008297:Male; D009820:Ohio; D011156:Population Density; D011157:Population Dynamics; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000453:epidemiology*; D012189:Retrospective Studies; D012424:Rural Population; D014505:Urban Population