Childhood cancer mortality and socioeconomic position in South Korea: a national population-based birth cohort study

Widening Social Inequalities in Cancer Mortality of Children Under 5 Years in Korea

BACKGROUND

To investigate the effect of parental social class on cancer mortality in children under 5 in Korea, two birth cohorts were constructed by linking national birth data to under-5 death data from the Statistics Korea for 1995-1999 (3,323,613 births) and 2010-2014 (2,297,876 births).

METHODS

The Cox proportional hazards model adjusted for covariates was used in this study.

RESULTS

Social inequalities of under-5 cancer mortality risk in paternal education and paternal employment status were greater in 2010-2014 than in 1995-1999. The gap of hazard ratio (HR) of under-5 cancer mortality between lower (high school or below) and higher (university or higher) paternal education increased from 1.23 (95% confidence interval, 1.041.46) in 1995-1999 to 1.45 (1.11-1.97) in 2010-2014; the gap of HR between parents engaged in manual work and non-manual work increased from 1.32 (1.12-1.56) in 1995-1999 to 1.45 (1.12-1.89) in 2010-2014 for fathers, and from 1.18 (0.7-1.98) to 1.69 (1.03-2.79) for mothers. When the parental social class was lower, the risk of under-5 cancer mortality was higher in not only adverse but normal births.

CONCLUSION

Social inequalities must be addressed to reduce the disparity in cancer mortality of children under 5 years old.

Role of Parental Social Class in Preterm Births and Low Birth Weight in Association with Child Mortality: A National Retrospective Cohort Study in Korea

PURPOSE

We explored the role of parental social class in preterm birth (PTB) and low birth weight (LBW) in association with child mortality in Korea.

MATERIALS AND METHODS

A total of 7,302,732 births in Korea between 1995 and 2007 were used for designing the national retrospective cohort study. Kaplan-Meier survival curves and Cox proportional hazard models were used to determine the risk of child death after adjusting for covariates.

RESULTS

Parental social class was associated with adverse birth outcomes and child mortality in Korea. Parental social class increased the strength of the relationship of adverse birth outcomes with child mortality. Child mortality was higher among PTB and LBW infants from parents with a lower social class than normal births from parents with a higher social class. In particular, the disparity in child mortality according to parental social class was greater for LBW and PTB than intrauterine growth retardation births. When one of the parents had a middle-school education or lower, the disparity in child mortality due to adverse birth outcomes was large regardless of the other spouse's educational status. Inactive economic status for the father, as well as an occupation in manual labor by the mother, increased the risk of child mortality.

CONCLUSION

Strong relationships for social inequalities and adverse birth outcomes with inequalities in child mortality in South Korea were found in this study. Tackling social inequalities, as well as reducing adverse birth outcomes, are needed to reduce the disparities in child mortality in South Korea.

Rural/urban residence and childhood and adolescent cancer survival in the United States

BACKGROUND

To the authors' knowledge, no previous study has examined the relationship between rural/urban residence and childhood or adolescent cancer survival in the United States. Using the Surveillance, Epidemiology, and End Results 18 registries database, the authors examined childhood and adolescent cancer survival by rural/urban residence as defined by Rural-Urban Continuum Codes (RUCCs).

METHODS

The authors obtained data from Surveillance, Epidemiology, and End Results 18 registries for individuals diagnosed at ages birth to 19 years with a first primary malignant cancer from 2000 through 2010. Rural/urban residence at the time of diagnosis was defined using both metropolitan/nonmetropolitan county classifications and individual RUCC categories. Cox proportional hazards regression was used to compute adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the association between rural/urban residence and cancer survival. The authors also examined effect modification by age group, sex, race/ethnicity, and cancer type.

RESULTS

Among 41,879 cancer cases, approximately 54.7% were non-Hispanic white, 54.3% were male, and 90.4% lived in a metropolitan county. Individuals living in nonmetropolitan counties versus metropolitan counties had a similar risk of cancer death (HR,  1.03; 95% CI, 0.94-1.13) as did those living in nonmetropolitan rural counties with <2500 individuals nonadjacent to a metropolitan area versus those living in metropolitan counties of ≥1 million individuals (HR,  0.98; 95% CI, 0.71-1.37). Evidence for effect modification largely was absent.

CONCLUSIONS

The results of the current study suggest that childhood and adolescent cancer survival in the United States does not vary by rural/urban residence at the time of diagnosis as defined by RUCCs. The widespread availability of public health insurance for children and adolescents and a nationwide network of pediatric cancer providers may explain this finding.

Socioeconomic disparities in childhood cancer survival in Switzerland

In this study, we investigated whether childhood cancer survival in Switzerland is influenced by socioeconomic status (SES), and if disparities vary by type of cancer and definition of SES (parental education, living condition, area-based SES). Using Cox proportional hazards models, we analyzed 5-year cumulative mortality in all patients registered in the Swiss Childhood Cancer Registry diagnosed 1991-2006 below 16 years. Information on SES was extracted from the Swiss census by probabilistic record linkage. The study included 1602 children (33% with leukemia, 20% with lymphoma, 22% with central nervous system (CNS) tumors); with an overall 5-year survival of 77% (95%CI 75-79%). Higher SES, particularly parents' education, was associated with a lower 5-year cumulative mortality. Results varied by type of cancer with no association for leukemia and particularly strong effects for CNS tumor patients, where mortality hazard ratios for the different SES indicators, comparing the highest with the lowest group, ranged from 0.48 (95%CI: 0.28-0.81) to 0.71 (95%CI: 0.44-1.15). We conclude that even in Switzerland with a high quality health care system and mandatory health insurance, socioeconomic differences in childhood cancer survival persist. Factors causing these survival differences have to be further explored, to facilitate universal access to optimal treatment and finally eliminate social inequalities in childhood cancer survival.

Understanding why children die in high-income countries

Many factors affect child and adolescent mortality in high-income countries. These factors can be conceptualised within four domains-intrinsic (biological and psychological) factors, the physical environment, the social environment, and service delivery. The most prominent factors are socioeconomic gradients, although the mechanisms through which they exert their effects are complex, affect all four domains, and are often poorly understood. Although some contributing factors are relatively fixed--including a child's sex, age, ethnic origin, and genetics, some parental characteristics, and environmental conditions--others might be amenable to interventions that could lessen risks and help to prevent future child deaths. We give several examples of health service features that could affect child survival, along with interventions, such as changes to the physical or social environment, which could affect upstream (distal) factors.

The association between socioeconomic status and survival among children with Hodgkin and non-Hodgkin lymphomas in a universal health care system

BACKGROUND

The association between socioeconomic status (SES) and cancer survival has been studied extensively in adults. However, little is known about this relationship in the pediatric population, specifically in jurisdictions with universal health care insurance programs. Our aim was to determine whether lower SES is associated with poorer survival in pediatric Hodgkin (HL) and non-Hodgkin lymphoma (NHL) patients in Ontario.

PROCEDURE

All incident cases of HL and NHL in children between 0 and 14 years old diagnosed in Ontario between January 1st, 1985 and December 31st, 2006 were identified through the Pediatric Oncology Group of Ontario Networked Information System. Neighborhood income quintile and material deprivation quintile at diagnosis were used as proxies for SES. Cox proportional hazards regressions were used to assess the association between SES and the risk of event-free or overall survival.

RESULTS

A total of 692 patients were included in the analysis: 302 HL and 390 NHL. SES was not associated with survival (overall or event-free) among HL and NHL patients (P > 0.05 for all four comparisons, i.e., HL/NHL, EFS/OS) after adjustment for age, sex, period of diagnosis, and disease stage. There were no differences in the distribution of disease stage across SES strata at the time of diagnosis. Similarly, the distribution of deaths among long-term survivors (survived ≥5 years from diagnosis) did not differ across SES strata (P > 0.05).

CONCLUSIONS

SES was not associated with risk of death among pediatric HL and NHL patients in Ontario. This was consistent through the cancer trajectory, including diagnosis, treatment, and survivorship.

Korean Environmental Health Survey in Children and Adolescents (KorEHS-C): survey design and pilot study results on selected exposure biomarkers

For the first nationwide representative survey on the environmental health of children and adolescents in Korea, we designed the Korean Environmental Health Survey in Children and Adolescents (KorEHS-C) as a two-phase survey and planned a sampling strategy that would represent the whole population of Korean children and adolescents, based on the school unit for the 6-19 years age group and the household unit for the 5 years or less age group. A pilot study for 351 children and adolescents aged 6 to 19 years in elementary, middle, and high school of two cities was performed to validate several measurement methods and tools, as well as to test their feasibility, and to elaborate the protocols used throughout the survey process. Selected exposure biomarkers, i.e., lead, mercury, cadmium in blood, and bisphenol A, metabolites of diethylhexyl phthalate and di-n-butyl phthalate and cotinine in urine were analyzed. We found that the levels of blood mercury (Median: 1.7 ug/L) and cadmium (Median: 0.30 ug/L) were much higher than those of subjects in Germany and the US, while metabolites of phthalates and bisphenol A showed similar levels and tendencies by age; the highest levels of phthalate metabolites and bisphenol A occurred in the youngest group of children. Specific investigations to elucidate the exposure pathways of major environmental exposure need to be conducted, and the KorEHS-C should cover as many potential environmental hazards as possible.

Childhood cancer mortality and birth characteristics in Korea: a national population-based birth cohort study

To examine the relationship between birth characteristics and childhood cancer mortality, a retrospective cohort study of Korean children was conducted using data collected by the national birth register between 1995 and 2006, which were then individually linked to death data. A cohort of 6,479,406 children was followed from birth until their death or until December 31, 2006. Poisson regression analyses were used to calculate rate ratios of childhood cancer deaths according to birth characteristics. A total of 1,469 cancer deaths were noted and the childhood cancer mortality rate was found to be 3.43 per 100,000 person-years in Korea during the period of 1995-2006. The birth characteristics examined in this study (i.e. , birth weight, gestational age, multiple births, parental ages, and number of siblings) were generally found to be not significantly associated with childhood cancer mortality, and the associations did not vary meaningfully with gender nor with cancer sites. However, among children aged 5-11 yr, higher birth weight was associated with elevated childhood cancer mortality (rate ratio = 1.28, 95% confidence interval 1.04-1.58). Our results offer no overall associations between childhood cancer mortality and birth characteristics, but suggest that the association may be specific to age group.