Marriage-based immigration, predominantly of female immigrants, has been a major driver of intra-Asian migration, especially in Japan, Taiwan and South Korea (hereafter Korea) [1]. In Korea, marriage-based immigration began in the 1980s, majority of which were between Japanese women and Korean men. Subsequently, it expanded to women from China and South-East Asia [2]. Marriage-based immigrant women (MIW) generally face difficulties, such as social prejudice, linguistic and cultural differences, child-rearing, and financial hardships [3]. A systematic review study reported that MIW in Korea showed relatively poor health outcomes [4].

The “healthy immigrant effect” is observed when immigrants tend to be healthier than the majority population in host countries [5]. However, those health benefits are not consistent. As the length of immigrants’ stay increase, their health status becomes similar to that of the natives; further, in old age, they show poorer health status than the locals [5, 6]. Recently, more than 45% of MIW in Korea reached the age of 40 or older [7]. The Korean government has provided targeted policies for MIW to effectively fulfill their expected social reproductive roles [8]. As the aging of MIW becomes visible, more attention is needed not only on their social reproductive but also on a more comprehensive health-related quality of life (HRQOL). HRQOL is a multi-dimensional concept that includes domains related to physical, mental, emotional, and social functioning [9]. Midlife transitions, such as menopause, negatively affect their quality of life [10].

In Korea, there has been a sharp increase over the past decade in research on the health of MIW [4, 11]. A recent meta-analysis showed that various studies attempted to identify the factors affecting the quality of life of MIW [11]; these factors included physical and mental health (depression, perceived health status) and psychosocial variables (social support, acculturation). However, the study subjects of most studies were young MIW in their 20s or 30s. Studies on the health of middle-aged MIW are, thus, scarce.

Japanese MIW occupy a unique position among MIW in Korea. Both counties have a relatively homogeneous race and culture and a socio-cultural background influenced by Confucianism [3]. Additionally, while other MIW came from developing countries for financial reasons, Japan was a developed country, with most Japanese migrating for religion-related reasons [3]. Furthermore, Japanese MIW perceived their quality of life to be lower than other MIW [12]. Indeed, the previous studies [12] reported that Japanese MIW were more vulnerable than others, with a low quality of life. However, sample in the previous studies [12, 13] were numerically small, with younger age groups that did not encompass the adequate scope of middle-aged Japanese MIW. It is important to note that Japanese women are a representative group of early MIW in Korea, with most being over the age of 40. Thus, further studies on middle-aged Japanese MIW can be the references to predict the HRQOL of the younger-generation MIW.

Therefore, the purpose of the present study was to identify the extent to which physical and mental health, as well as psychosocial variables can predict HRQOL among Japanese middle-aged MIW in Korea. The study can provide the evidence necessary for future interventions and policymaking to improve the HRQOL of middle-aged MIW.

Most countries are increasingly being affected by international migration. Core industrialized countries in East Asia, including Korea, have now emerged as new migration destinations [1]. With the first generation of MIW in East Asia now reaching middle or old age, focused investigations into their HRQOL have become necessary. This study demonstrates that depression is the strongest predictor of HRQOL. Social support, perceived health status, and household income also accounted for significant independent variances in the model. However, menopausal symptoms, disease morbidity, and acculturation did not provide any additional value in predicting HRQOL in Japanese MIW.

Depression is a common mental disorder and a major contributor to the overall global burden of diseases, especially in women [22]. Recent studies have consistently emphasized the importance of mental health interventions in relieving depression, especially for improving HRQOL in older immigrants [22, 23]. In a study of Lee et al. on Korean-Chinese male and female immigrants [24], depression was also the strongest predictor of HRQOL. Among marriage immigrants, 33.4% in their 50s and 42.8% in their 60s reported having experienced depression in the previous year [7]. This is about three to four times higher than that reported by native Koreans in the same age group [25]. This study’s participants were also more depressed than Japanese middle-aged women living in their home countries [26]. In a previous study comparing the prevalence of depression in the first-generation immigrants aged 50 years or older and residents without a history of migration in 11 European countries, the odds ratio for depression in immigrants was 1.42 [22]. Moreover, it should be noted that 37.1% of this group scored 16 or above on the J-CES-D scale, which is indicative of clinically significant depression. This is similar to an earlier study [27], which reported that 30% of elderly Korean immigrants living in the United States had depressive symptoms. While migration may provide opportunities for a better life, the risk of failure, loss, decrease in personal networks, and social values dissimilar to those in the country of origin could negatively affect mental health in immigrants [22]. The process of aging may pose an additional burden for immigrants, which may place them at increased risk for mental health problems.

Our study’s findings indicate that social support is a key protective factor in HRQOL. This is consistent with a systematic review study [4]. In the 2018 Korean National Survey of Multicultural Families [7], 30~40% of the respondents answered that there is no one in Korea to discuss it with or to ask for help, expect for their family members, so there is a high probability that it will be difficult to mobilize appropriate social resources when necessary because social relationships are not developed. One interesting finding is that the social support enjoyed by Japanese MIW was higher than that of middle-aged Korean women [28]. This is contrary to a previous study, which reported that immigrants’ social support is generally weak [27]. It should be noted that most of our study participants were recruited from churches. Agyekum and Newbold reported that the church is important for the quality of life of immigrants, and that religious activities, such as praying, affect the spiritual quality of life [29]. Middle-aged South Asian women who emigrated to Canada reported that attending community support programs facilitated their midlife transition, while limited support from their social circle became a barrier [30]. Therefore, community organizations play a pivotal role in providing strong social solidarity to immigrants for settling and adapting to host countries [29].

Perceived health status was also found to be a significant predictor of HRQOL. This is consistent with a previous study [31]. In a study of HRQOL in Japanese and Australian middle-aged women, physical and mental symptoms were reported to have a negative effect on physical function [31]. While 65.7% of migrant workers who had resided in Korea for more than 10 years perceived their general health as good [6], only 11.8% of this study participants self-reported good health. Among our study’s participants, 65.9% were in their 50s or older, while in Chae et al.’s study, this figure was 43.1%, and 52.7% were male [6]. We assume that majority of this study participants perceived their health to be poor might be related to old age, female gender, and high rates of depressive symptoms.

Household income emerged as a significant predictor of HRQOL. HRQOL of MIW with a monthly household income of less than 2,000,000 KRW was significantly lower than that of MIW with a monthly household income of 3,000,000 KRW or more. Forty percent of the study participants had a monthly household income of less than 2,000,000 KRW-an amount less than half of Korea's average monthly household income [32]. Zou et al. suggest that being employed and possessing adequate life skills can facilitate midlife transition [30]. Although the Korean government has introduced various programs to assist MIW access the labor market, more comprehensive and effective employment and education programs should be prioritized to help MIW integrate into society, as well as to prevent poverty in old age [8, 30].

Although menopausal symptoms and acculturation were not significant in the final regression model, these had a significant relationship with HRQOL in univariate analysis. Acculturation in this study participants was higher than in Korean immigrants living in the United States for 21.7 years [21]. It is known that acculturation starts in early life, and high education level, voluntary migration, and cultural proximity are associated with positive adaptations [33]. In addition, as MIW migrate alone to form families with Koreans, they are fully exposed to the culture of the host country. Similarly, Lee et al. [24] reported that acculturation did not affect the HRQOL of Korean-Chinese immigrants. As acculturation phenomena result from contact between two or more cultures, research on acculturation is complex and must be comparative [33]. Further studies are needed to compare the acculturation of immigrants from diverse ethnic backgrounds and to understand the relationship between acculturation and HRQOL.

Although regular exercise was not a significant predictor of HRQOL, we found a severe lack of exercise among middle-aged MIW. Most of the study participants (84.2%) did not exercise regularly. Anderson and Yoshizawa reported that 36.3% of Japanese middle-aged women did not exercise regularly, and the amount of activity was a significant predictor of HRQOL [31]. Exercise is consistently reported as having an antidepressant effect [34]. It is thus logical that the lack of exercise among our study participants might be associated with a high rate of depressive symptoms.

This study had some limitations. First, only Japanese women living in the two regions were surveyed. Japanese women who voluntarily participated in community activities might have been more active and socially connected. Furthermore, the convenience sample limits the generalizability of our results. Another limitation was that two data collection modes, face-to-face and mail surveys, were used in this study. A preliminary survey was used to confirm that there would be no difficulty in completing the self-administered questionnaire. However, the return rate of the mail survey was only 67.9%, and most data that could not be used in the analysis came from the mail survey due to item non-response. When using mail surveys with immigrants, greater attention should be paid to the questionnaire design stage. In addition, because the cross-sectional nature of the present study, it precludes understanding how the influencing factors of HRQOL among Japanese MIW were changed from immediately after immigrating to Korea to the time of the survey.

Despite these limitations, to the best of our knowledge, this is the first study to examine influencing factors on HRQOL among middle-aged MIW residing in Korea. This study highlights the need for greater attention to the mental health of MIW by nursing researchers, practicing nurses, and policy makers so that timely interventions are implemented and MIW can lead healthy and fulfilling life. Further nursing studies are needed to develop intervention programs for the management of depressive symptoms of immigrant women and evaluate their effectiveness.

Depression is the strongest predictor of HRQOL in Japanese middle-aged MIW. More than a third of MIW had depressive symptoms. Social support, perceived health status, and household income also accounted for significant independent variances in the model. In times of rapid growth in global migration and the aging of immigrants in new migration destination countries, nursing interventions and public health policies for MIW should prioritize improving mental health, building social support, and facilitating disease management. In addition, social and employment policies that can help MIW transition to a healthy midlife are needed.