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An examination, with a meta-analysis, of studies of childhood leukaemia in relation to population mixing.

ABSTRACT: BACKGROUND: Marked influxes of people into rural areas, termed rural population mixing (PM), have been associated with excesses of childhood leukaemia (CL), consistent with mini-epidemics of a mainly immunising, subclinical infection to which CL is a rare response. For such situations of rural PM would promote contacts between infected and susceptible individuals, the latter tending to have a higher than average prevalence in rural or isolated areas. Confusion has arisen from some workers applying the term PM to non-rural situations lacking known recent change. METHODS: Available PM studies using the original definition of influxes were examined, a meta-analysis carried out of studies of CL in relation to exposure to high levels of rural PM, and also a detailed analysis by age group. RESULTS: The meta-analysis of 17 studies shows a significant CL excess in association with rural PM: overall relative risk (RR) at ages 0-14: 1.57; 95% confidence interval 1.44-1.72; at 0-4 years 1.72 (1.54-1.91). This contrasts with the absence of an excess of CL in similarly exposed urban areas (RR 1.00; 0.93-1.07), pointing to a high level of immunity there. The mixed results of studies using other definitions of PM were summarised. The excess associated with rural PM below age 2 years (RR 1.51; 1.17, 1.92) was not appreciably different from that at later childhood ages. CONCLUSION: Much of the inconsistency among studies ostensibly about CL and PM reflects the use of definitions other than that originally proposed. The broad similarity of the CL excess below age 2 with that at older childhood ages is inconsistent with the Greaves' delayed infection hypothesis, since any infection underlying the former is difficult to consider as delayed.

SUBMITTER: Kinlen LJ

PROVIDER: S-EPMC3461174 | biostudies-other | 2012 Sep

REPOSITORIES: biostudies-other

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Project description:ObjectivesSurvival among children diagnosed with acute lymphoblastic leukaemia (ALL) has increased considerably. However, morbidity in survivors constitutes a potential increasing burden not limited to secondary health care. Our objectives were to compare health care utilisation, including both primary and secondary health care, between childhood ALL survivors and matched references up to 15 years after curative treatment. Moreover, to increase knowledge on survivors' health service seeking behaviour as time from treatment elapsed.Design and settingA Danish population-based matched cohort study linking multiple nationwide registries.Participants675 cases, diagnosed with childhood (1.0-17.9 years) ALL between 1994 and 2015, and 6750 matched references sampled randomly from the source population (matched on age, gender and geographical region).Primary outcome measuresRepeated consultations in general practice and hospital (outpatient and inpatient) estimated as yearly rates from 2.5 years after diagnosis and onwards. We compared cases and references with yearly incidence rate ratios (IRRs) from negative binomial regression models.ResultsSurvivors of childhood ALL had a mean number of yearly daytime contacts in general practice of 4.75 (95% CI 4.41 to 5.11) the first year, corresponding to an IRR of 1.85 (95% CI 1.71 to 2.00); decreasing to 1.16 (1.01 to 1.34) after 15 years, and without significant impact of gender (p=0.894) or age (p=0.399). For hospital contacts, ALL survivors had a mean number of yearly contacts of 14.21 (13.38-15.08) the first year, corresponding to an IRR of 31.50 (28.29-35.07); decreasing to 2.42 (1.59-3.68) after 15 years. No differences were found across calendar time.ConclusionsALL survivors used significantly more health care services across sectors than the reference population. Decreasing use over 15 years illustrated the dynamics of health care needs; this knowledge may inform the future organisation of integrated follow-up programmes.Trial registration numberNCT03985826.

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An examination, with a meta-analysis, of studies of childhood leukaemia in relation to population mixing.

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