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.

Femur Fractures in Parkinsonism: Analysis of a National Sample Cohort in South Korea

BACKGROUND AND PURPOSE: Falling with a femur fracture is a serious event that negatively affects the quality of life of elderly individuals as well as patients with parkinsonism. This study investigated the association between parkinsonism and femur fracture and compared the risk of femur fracture between subjects with and without parkinsonism. METHODS: This study examined a population-based matched cohort constructed using the National Sample Cohort data set, which comprises approximately one million subscribers to medical insurance and aid in South Korea. Subjects with parkinsonism during 2003–2013 were identified as the exposed group, and up to five individuals matched for age, sex, and index years were identified as the controls for each parkinsonism subject. The risk of femur fracture for parkinsonism was evaluated using Cox regression. RESULTS: The incidence of femur fracture according to age, sex, and body mass index varied significantly between subjects with parkinsonism and controls (p<0.001). The presence of parkinsonism was associated with a higher risk of femur fractures for males [hazard ratio (HR)=2.85, 95% confidence interval [CI]=1.87–4.34], subjects younger than 65 years (HR=2.89, 95% CI=1.64–5.11), and underweight subjects (HR=3.90, 95% CI=1.82–8.35). The adjusted HR for femur fracture with parkinsonism was highest within 2 years of the disease diagnosis (HR=3.10, 95% CI=2.12–4.53). CONCLUSIONS: Our study found that the presence of parkinsonism is more strongly related to femur fracture in males, and increases the influence of traditional risk factors on femur fracture. It is necessary to consider how factors associated with the amount of ambulatory activity–even in an early diagnosed state–can play an important role in femur fracture in subjects with parkinsonism.

Trends of Social Inequalities in the Specific Causes of Infant Mortality in a Nationwide Birth Cohort in Korea, 1995–2009

The relationship between social disparity and specific causes of infant mortality has rarely been studied. The present study analyzed infant mortality trends according to the causes of death and the inequalities in specific causes of infant mortality between different parental social classes. We analyzed 8,209,836 births from the Statistics Korea between 1995 and 2009. The trends of disparity for cause-specific infant mortality according to parental education and employment were examined using the Cox proportional hazard model for the birth-year intervals of 1995–1999, 2000–2004, and 2005–2009. Adjusted hazard ratios were calculated after adjusting for infants' gender, parents' age, maternal obstetrical history, gestational age, and birth weight. An increasing trend in social inequalities in all-cause infant mortality according to paternal education was evident. Social inequalities in infant mortality were greater for “Not classified symptoms, signs and findings” (International Classification of Diseases 10th revision [ICD-10]: R00–R99) and “Injury, poisoning and of external causes” (S00–T98), particularly for “Ill-defined and unspecified causes” (R990) and “Sudden infant death syndrome (SIDS)” (R950); and increased overtime for “Not classified symptoms, signs and findings” (R00–R99), “Injury, poisoning and of external causes” (S00–T98) and “Conditions in perinatal period” (P00–P96), particularly for “SIDS” (R950) and “Respiratory distress syndrome of newborns (RDS)” (P220). The specific causes of infant mortality, in particular the “Not classified causes” (R00–R99 coded deaths) should be investigated more thoroughly to reduce inequality in health.