The Relationship between Breastfeeding and Parental Socioeconomic Status: an analysis of the Korea National Health and Nutrition Examination Survey ( 2013 ~ 2017 )


 Background: The importance of breastfeeding is well known. One of important factors affecting breastfeeding is socioeconomic status. We investigated the relationship between socioeconomic status and breastfeeding to promote future breastfeeding projects.Methods: Data were collected from the 2013 - 2017 Korea National Health and Nutrition Examination Survey (KNHANES). We evaluated the demographic information and parents’ socioeconomic status of 814 children, aged 12 ~ 60months.Results: Of the 814 children, 743 (92.2%) were breastfed. In univariate analysis, parents’ age and education level were related to breastfeeding (P < 0.05). In logistic regression analysis, mothers’ education level (≤ 13 years: odd ratio[OR], 8.57; 95% confidence interval [CI], 2.73-26.87), mothers’ income level (third quartile: OR, 2.94; 95% CI, 1.2-7.23), fathers’ age (20s: OR, 0.3; 95% CI, 0.09-0.98), fathers’ education level (10-12years: OR 4.85; 95% CI, 1.4-16.76 and 13years: OR, 18.55; 95% CI, 5.23-65.81), fathers’ income (third quartile: OR, 2.72; 95% CI 1.02-7.22) were associated with breastfeeding (P < 0.05).Conclusion: Higher parental income and education level and fathers’ age were positively associated with breastfeeding in Korea. The establishment of future breastfeeding projects should be considered target parents in Korea and other countries.

However, despite the recommendation to breastfeed exclusively for about the first 6 months, less than 50% of infants were exclusively breastfed in the first 3 months, and 24.9% were exclusively breastfed in the first 6 months. 9tween 1985 and 1995, the global rates of exclusive breastfeeding increased by 2.4% per year on average (increasing from 14% to 38% over 10 years). 10The Global Breastfeeding Collective, led by UNICEF and the WHO, set a target to increase the global rate of exclusive breastfeeding in the first 6months of life: at least 50% by 2025 and at least 70% by 2030. 10,11 Korea, the rates of breastfeeding at 6months of age increased to 60.8% in 2010 and 62.3% in 2013; however, it decreased to 55.6% in 2016.The Korean Ministry of Health and Welfare's Fourth National Health Plan aims to increase to 66.8% by 2020. 12though the socioeconomic factors associated with breastfeeding have been broadly reported, scant studies have examined these variables in Korea.Therefore, we explored the relationship between socioeconomic factors and breastfeeding in Korea using data from the Korean National Health and Nutrition Examination Survey(KNHANES).Information from this study will help increase breastfeeding practice and the overall breastfeeding rate.

Data source
This study was conducted using the raw data from the KNHANES of the sixth (2013 ~ 2015) and the seventh term (2016 ~2017).The KNHANES is a statutory survey on people's health behavior, prevalence of chronic diseases, and food and nutrition practices.KNHANES was conducted in a threeyear period from the first (1998) to the third period (2005), and has since been reorganized into a year-round survey system, and has been conducted annually from the fourth term (2007-2009) to the present day.KNHANES consisted of a cross-sectional survey composed of a health interview survey and a health examination survey, and a nutrition survey.All survey protocols were approved by the Korea Centers for Disease Control & Prevention (KCDC) Institutional Review Board.Written informed consent was obtained from all participants before the survey commencement.
In this study, we included 1,534 children over 12 months under 60 months out of 31,098 participants in the sixth and seventh terms.Of these, we excluded 718 participants who were no information of breastfeeding(n = 365), did not provide socio-economic data(n = 41), and were raised by single parents(n = 312).The remaining 814 participants were included in the final analysis (Fig. 1)

Study design
This study employed a cross-sectional design.All data are available from the KNHANES database (http://knhanes.cdc.go.kr/knhanes).We categorized data into two groups (non-breastfed, breastfed).

Data analysis
Statistical Package for the Social Sciences (SPSS) complex sample procedures were employed since KNHANES data were collected through a representative, stratified, and clustered sampling method.
Participants' characteristics are presented as a percentage and a 95% confidence interval.
Differences between the breastfeeding and non-breastfeeding groups are reported using chi-square test.We conducted a logistic regression analysis to identify the relationships between factors and breastfeeding.We first adjusted for maternal education level and income level (model 1) and then for the variables in model 1 plus paternal age, education level and income level.Statistical analysis was conducted using SPSS version 21.0 (SPSS Inc.Chicago, IL, US).For all analyses, p-values were twotailed, and a P value < 0.05 was considered significant.

Participants' characteristics
As shown on Table

Discussion
In this study, we revealed that the higher parents' income and education level, the higher the breastfeeding rate; and the younger fathers' age, the lower the breastfeeding rate.
Multiple factors influence breastfeeding.These factors were classified into four groups: demographic, biological, social, and psychological.Demographic factors that affect the breastfeeding rate include race, maternal age, marital status, socioeconomic status, and education level. 13In this study, we examined demographic variables that affect breastfeeding.
In this study, most parents were in their 30s and most breastfed their infants; however parental age did not affect breastfeeding.Other studies showed same results. 14,157][18] Oakely et al 19 reported that the younger the mother was, the less likely she was to breastfeed or to stop breastfeeding within 6 weeks.We posit that younger mothers lack knowledge and awareness of breastfeeding.
Banu et al 20 stated that the higher the parents' education level, the higher the exclusive breastfeeding rate and longer duration of the exclusive breastfeeding.In this study, parents' education level was also related to breastfeeding.The higher the mother's education level, the higher the breastfeeding rate.In model 1, maternal education level (≥ 13years) revealed highest breastfeeding rate.2][23][24][25] Even for mothers with a job, breastfeeding rate is estimated to be high, because the higher the level of education, the higher the occupational status, the better the working environment and the better knowing the benefits of breastfeeding.In middle-and low-income countries, the relationship between breastfeeding and mothers' education level varies.Some studies have reported a negative relationship between mothers' education level and the breastfeeding rate owing to quick return to work. 18,26Another study showed a higher parental education level was associated with a higher breastfeeding rate and exclusive breastfeeding. 27 found a positive association between father's education level and breastfeeding.Similar finding has been reported by Flacking et al 28 , who found that the lower the fathers' education level, the lower the breastfeeding rate.We posit that this is related to family income.Because higher education often results in a better income, mothers may not need to work and can focus on parenting.However, other study showed that mothers'-but not fathers'-education level was related breastfeeding, 17 or that parental education level was not related to breastfeeding. 29,30rther, in this study, there was no relationship between the mother's income and breastfeeding, however, the higher the income of the father, the higher the breastfeeding rate.This is believed that non-working mother (full-time housewives) composed 65.17%, father is main source of family income.
Therefore, the higher the father's income, the greater the mother's devotion to child care, and breastfeeding.Similar results have been reported that the lower the father's income level, the shorter the breastfeeding duration. 28This may be related to easy finding a job for mother.
On the contrary, Wallby et al 31 reported that higher breastfeeding rate in low-income households.This is believed to be due to the fact that there are no economic condition to choose a different formula besides breast milk and no easy finding a job for mother.Victoria et al 4 stated that highincome, better-educated women breastfeed more commonly in high-income countries.Due to economic benefits, the lower the household's gross income, the higher the breastfeeding in lowincome and middle-income countries.However, in other studies, household income did not affect breastfeeding. 15,29 ernal job status is variable that has been associated with breastfeeding.Previous studies 14,18,24 revealed that full-time houseswives have higher breastfeeding rates than mothers with work and the shorter the time to return to work after childbirth, the shorter the breastfeeding period.It is estimated that they stop breastfeeding because they have less time to care for the child while working.However, we did not find a significant association between breastfeeding and parental job status.Importantly, our results shed light on some socioeconomic factors associated with breastfeeding; however, this study has some limitations.The utilized data were collected through self -report, and this is a source of recall bias which may have either underestimated or overestimated the relationship between the breastfeeding and socio-economic status.Further, causal relationships cannot be confirmed owing to the cross-sectional design of the KNHANES.Also, because it is a survey study, it was not possible to analyze the factors affecting breastfeeding according to the duration of breastfeeding.In addition to the factors used in this study, it is considered that studies on various social factors such as breastfeeding education, use rooming-in, use of postpartum care center, parental leave, and establishment of a breastfeeding room in the workplace are necessary.

Conclusion
This large population-based study demonstrated that parents' income and education level and fathers' age were positively related to breastfeeding.Our results are especially helpful in establishing evidence-based health policies on breastfeeding in Korea and other countries.To increase the breastfeeding rate and exclusive breastfeeding, further research should explore the reasons why parents stop breastfeeding.

Flow
chart of the sample selection process of the study population

Table 3
The association between breastfeeding and socioecon