The growth status of North Korean refugee adolescents in South Korea: comparison with South Korean adolescents

Abstract Aim To assess the growth status of North Korean refugee adolescents (NKRA) living in South Korea (SK) and compare their growth status with that of SK adolescents (SKA). Subjects and methods NKRA were interviewed from 2017 to 2020, whereas the data for SKA were from the 2016 to 2018 Korea National Health and Nutrition Examination Surveys. SKA and NKRA were matched by age and gender in a 3:1 ratio and 534 SKA and 185 NKRA were enrolled. Results After adjusting for the covariates, NKRA had greater prevalences of thinness (odds ratio [OR], 11.5; 95% confidence interval [CI], 2.9–45.6) and obesity (OR, 12.0; 95% CI, 3.1–46.1) than SKA, but were not of short stature. In comparison with SKA in low-income families, NKRA had similarly greater prevalences of thinness and obesity, but not of short stature. As the length of stay of NKRA in SK increased, the prevalence of short stature and thinness did not decrease, while the prevalence of obesity increased significantly. Conclusion Although they had lived in SK for several years, NKRA had greater prevalences of thinness and obesity than SKA and the prevalence of obesity increased significantly with the length of stay in SK.


Introduction
The great North Korean (NK) famine in the mid-1990s resulted in hundreds of thousands of refugees (Lankov 2006), some of whom entered South Korea (SK).The Ministry of Unification reported that 33,826 NK refugees (NKRs) had entered SK by March 2022, of which 5107 (15.1%) were under the age of 19 (Ministry of Unification 2022).Since this number includes only children and adolescents born in NK, if those born in a third country or SK were included, the number of NKR adolescents living in SK might be much higher (Choi 2020).
NKR adolescents showed growth faltering and weight loss due to extreme stress and lack of food during their escape from NK to SK (Baek et al. 2007;Choi and Kang 2017), and their growth status has not improved after settling in SK (Lee and Park 2013).
Adolescence is a sensitive period when individuals are exposed to various risks before becoming adults.It is the growth period with the highest nutritional demands, so it is important to have a nutritionally appropriate diet during this period and it is an especially important time to form healthy eating habits that can last a lifetime (Jung et al. 2020).Therefore, it is necessary to actively intervene to identify the growth status of NKR adolescents and maintain good nutritional status.
Several studies have evaluated the growth status of NKR adolescents (Chang et al. 2000;Pak 2004Pak , 2010;;Kim 2005;Lee et al. 2011).Those authors reported that NKR adolescents had greater prevalences of stunting, underweight, and wasting than SK adolescents.However, most studies measured small numbers of subjects (Kim 2005;Lee et al. 2011) or used screening data immediately after they defected (Pak 2004(Pak , 2010)).Therefore, we assessed the growth status of NKR adolescents settled in SK and compared their status with that of SK adolescents.To determine whether there is a gap in the growth status of NK and SK adolescents after excluding the impact of the low socioeconomic status (SES) of NKRs, we compared the growth status of NKR adolescents with that of SK adolescents from low-income families.

NKR adolescents
This study enrolled NKR adolescents aged 13-18 years who had at least one parent who was an NKR.From June 2017 to May 2019, 198 subjects were surveyed through regional Hana Centres, alternative schools and non-governmental organisations.A Hana Centre is a public centre that supports the adaptation and stable independence of NKRs living in local communities.The investigators used structured questionnaires to interview participants face-to-face.Of the 198 NKR adolescents, seven were excluded due to missing height and weight data and six were born in SK.Ultimately, this study included 185 NKR adolescents.
Before the survey, the trained investigators explained the purpose of this study, that the collected data would not be used for any purpose other than the study and that participants could participate voluntarily and drop out at will.Informed consent was obtained from both the NKR adolescents and their guardians.This study was approved by the institutional review board of Chosun University (IRB No. 2-1041055-AB-N-01-2017-0025).

SK adolescents
For SK adolescents, the data from the 2016-2018 Korea National Health and Nutrition Examination Surveys (KNHANES) were used.KNHANES is an annual national survey conducted by the Korea Disease Control and Prevention Agency (KDCA) that produces reliable representative data at the national level through interviews, blood tests and nutrition surveys.Detailed information on KNHANES is available in Kweon et al. (2014).There were 24,269 participants in the 2016-2018 KNHANES, of which 1433 were aged 13-18 years.From these, 573 SK adolescents were selected by age-and gender-matching with NKR adolescents in a 3:1 ratio.Thirtynine were excluded due to missing height and weight data.Ultimately, 534 SK adolescents were included in this study.

General characteristics
For the NKR adolescents, sex, age, birth country, length of stay in SK and nationality of the birth mother and birth father were surveyed.Height was measured after taking off shoes, pulling in the chin and keeping the gaze level using an InKids ultrasonic portable extensometer (InLab S50; InBody, Seoul, Korea) that can measure height up to 200 cm in 0.1 cm units.Weight was measured using a digital scale (CAS HE-58; CAS, Yangju, Korea) to 0.1 kg without wearing outerwear or accessories.Body mass index (BMI) was calculated as body weight (in kg) divided by height squared (in m 2 ).
For SK adolescents, using the 2016-2018 KNHANES, sex, age, height, weight and quartiles of monthly household income were acquired.The quartiles of monthly household income were reclassified into high and low (highest and second highest vs. second lowest and lowest).

Growth status
The growth status was estimated using the 2017 Korean National Growth Charts for children and adolescents jointly developed by the Korea Paediatrics Society and KDCA (2017).Korean National Growth Charts are percentile curves showing the distribution of anthropometric measurements, including the height and weight of children and adolescents in Korea.Short stature was defined as a height-for-age z-score (HAZ) of less than À2 standard deviations (SD).Thinness was defined as a BMI-for-age z-score (BMIZ) of less than À2 SD.Obesity was defined as a BMIZ of greater than 2 SD.

Statistical analysis
Statistical analyses were performed using SPSS 23.0 (IBM, Armonk, NY, USA).The general characteristics of the participants are presented as a number (%) or the mean ± SD.Differences between NKR and SK adolescents were evaluated using the v 2 test or Student's t-test.The odds ratios (ORs) with 95% confidence intervals (CIs) for the prevalence of short stature, thinness and obesity were compared using a multiple logistic regression model adjusted for sex, age and birth country.The level of statistical significance was set at p < .05for all statistical tests.

General characteristics of NKR adolescents and SK adolescents
Table 1 summarises the general characteristics of the 719 adolescents (185 NKR and 534 SK).NKR adolescents were significantly shorter (p ¼ .001),thinner (p < .001),more obese (p < .001)and had a lower HAZ (p < .001)and higher WHZ (p ¼ .003)than SK adolescents.However, there were no significant differences in age, weight, BMI, WAZ, or BMIZ between NKR and SK adolescents.The countries of birth of NKR adolescents were China (67.8%) and NK (32.2%).The most common nationality of the birth mother was NK (98.9%), while those of the birth father were China (64.3%),NK (32.4%) and SK (3.3%).The monthly household income of SK adolescents was low in 33.5% and high in 66.5%.
The growth status among NKR adolescents by the lengths of stay in SK Figure 1 shows the ORs of the prevalences of short stature, thinness and obesity among NKR adolescents by the length of stay in SK.The adjusted ORs show that the prevalence of obesity (OR, 3.4; 95% CI, 1.0-11.0) of NKR adolescents with a length of stay ! 5 years was significantly higher than in those with a shorter length of stay, while there were no differences in the prevalences of short stature and thinness.

Discussion
We assessed the growth of NKR adolescents living in SK and compared it with that of SK adolescents.Our results showed that after adjusting for covariates, NKR adolescents had significantly higher prevalences of thinness and obesity than SK adolescents, but not short stature.A previous study reported that 63.8% of NKR adolescents experienced life-threatening food shortage while escaping NK (Baek et al. 2007).Another study of NKR adolescents living in China found that most were stunted (62.3%) and underweight (60.6%) (Lee and Lee 2013).While these previous studies assessed the growth of NKR children and adolescents immediately after escaping from NK, our study found that the growth of NKR adolescents showed a significant gap from that of SK adolescents, even after settling in SK for several years.NKR adolescents are under tremendous stress to adapt to a new culture and experience feelings of inferiority, isolation, frustration and social discrimination (Yoo et al. 2004).These psychological stresses may have influenced the increased growth faltering of NKR adolescents.Moreover, they had harsh childhoods and this experience was embodied and thus it would have been difficult to overcome after they moved to SK.We found that the prevalences of thinness and obesity among NKR adolescents were significantly higher than in SK adolescents in low-income families.Previous studies of growth status according to SES in Korea showed that subjects with low SES had a higher risk of growth faltering than those with high SES (Yoon 2002;Kim et al. 2007Kim et al. , 2015;;Jang et al. 2011).In a settlement survey of NKRs in SK (Korea 1.1-72.6)11.1(1.3-93.2) Obesity SK adolescents in low-income families 1.0 1.0 NKR adolescents 12.3(1.6-96.0)10.8(1.3-88.1)OR: Odds Ratio; NKR: North Korea refugee; SK: South Korea.a Adjusted by sex, age, birth country.

Figure 1 .
Figure 1.ORs (95% CI) of the prevalences of short stature, thinness and obesity among North Korea refugee adolescents by the length of stay in SK (Reference: <5 years stay in South Korea).

Table 1 .
General characteristics of NKR adolescents and SK adolescents.

Table 2 .
Comparisons of the prevalence of short stature, thinness and obesity between NKR adolescents and SK adolescents.Adjusted by sex, age, birth country.
OR: Odds Ratio; NKR: North Korea refugee; SK: South Korea.a

Table 3 .
Comparisons of the prevalence of short stature, thinness and obesity between NKR adolescents and SK adolescents in low-income families.