Grandparenting has become a common social phenomenon due to the increase in overlapping lives between grandparents and grandchildren, as well as young mothers returning to the workforce[1–3]. In this context, the impact of grandparenting on their physical and mental health has drawn widespread scholarly attention[4, 5]. For example, life satisfaction is one of the hot spots in grandparenting studies and a significant association has been found[5–8]. Population migration is a key issue and a significant factor of Chinese population’s sustainable development. In statistics, there are 264 million elderly people, and 13.5 million elderly migrants in China[9, 10]. Prior studies have shown that migration is often accompanied with language and cultural differences, and unfamiliar living environments, which could lead to difficulties in the social integration[11, 12]. Due to the dual threats of aging and migration, elderly migrants suffer a worsen health and well-being than those with no migration experience[11, 13, 14]. Grandparenting is an important reason for the migration of elderly migrants. However, few studies have drawn attention to the impact of grandparenting on life satisfaction among elderly migrants and we know little about the underlying mechanisms. In China, with the population aging, migration and full opening of the two-child policy, there may be a significant expansion of the size for elderly migrants who will be involved in grandparenting. Thus, we conducted this study aimed at examining the impact of grandparenting on life satisfaction among Chinese elderly migrants, and attempted to explain the underlying mechanisms that link them.
1.1 Grandparenting and life satisfaction
Grandparenting refers to the behavior that grandparents provide care to their minor grandchildren, and invest time, energy, emotion, economy, material and other aspects of support. The role of grandparent is a crucial aspect in later life and most people aged ≥ 50 face this transition. In statistics, almost 50% of grandparents participate in the care for their grandchildren in China[15, 16]. And there is a similar proportion in Europe, although the proportions vary between countries. Life satisfaction reflects the comparison between one's life expectations and actual life situation[18, 19]. As an important indicator of subjective well-being, it also plays an important role in people's lives. Previous studies have found that grandparenting is significantly associated with grandparents’ life satisfaction. But the results have yielded inconclusive.
According to the theory of role accumulation, multiple roles can bring them more power, prestige and social identity, which may affect their health in a positive pathway. When elderly people become grandparents, they can derive satisfaction and emotional benefits from the grandparenting role. Several studies have found that grandparenting is beneficial to grandparents’ health and well-being, including lower depression, higher self-reported health[5, 23] and life satisfaction[5, 6, 8]. In contrast, the theory of role strain argues that when a person is in multiple roles, such as spouse, grandparent or colleague, role conflict can put strain on their role obligations. Grandparenting make them suffer negative health outcomes[25, 26]. In addition, some researchers argue that the level of care and regional cultural differences may also influence the effects of grandparenting on health and well-being[27, 28]. For example, in China and some other East Asian countries, multigenerational co-habitation is considered a desirable living arrangement that would promote filial piety and family solidarity, and grandparents regard participating in the care of their grandchildren as a responsibility. Researchers often found that grandparenting is positively associated with health and well-being in studies of East Asian countries[8, 22, 27]. However, in the USA, grandparents would not assume the responsibilities of grandchildren care unless their adult child was in a period of crisis, such as poverty, substance abuse and incarceration[7, 29, 30]. Custodial care is a relatively common phenomenon and is well investigated in these countries. Studies show that custodial care promotes negative effects on grandparents’ health and well-being[7, 25]. A recent systematic review shows that custodial grandparents are more likely to report poorer perceived health and higher levels of psychological distress than non-custodial caregivers and non-caregivers in the USA. Furthermore, the intensity of care varied may also influence the effects of grandparenting on health and well-being. For example, (Tang et al., 2016) found that low to medium levels of care were positively associated with life satisfaction compared to high levels of care and no care. (Xu et al., 2012) found that the intensity of grandparenting was positively associated with grandparents’ life satisfaction.
1.2 Grandparenting, loneliness, self-esteem and life satisfaction
In addition to the direct impact of grandparenting on grandparents’ life satisfaction, it is of great interest to examine the potential mechanisms involved in this pathway. Loneliness is the subjective feeling of inadequate social relations. Up to one-third of elderly people suffer varying degrees of loneliness[36, 37]. In past studies, researchers have found that the feeling of loneliness is a core factor affecting the overall health and well-being of all age groups, especially elderly people, such as higher levels of depression, anxiety, and lower levels of life satisfaction[40–42]. Grandparenting facilitates the interaction between grandparents and their grandchildren. Previous studies have confirmed that grandparenting is negatively correlated with loneliness. For example, Tang et al.(2016) found that Chinese grandparents who participate in grandchild care had a lower level of loneliness than non-caregivers. Similar result was also found in a German study. Overall, grandparenting may alleviate loneliness and further improve life satisfaction. So, we speculate that loneliness mediates the relationship between grandparenting and life satisfaction among elderly migrants.
Self-esteem can be conceptualized as “self-regard, an evaluation of one's worthiness” and it is an important indicator of a successful life. Several studies have found that there is a significant correlation between self-esteem and life satisfaction[41, 46–48]. This holds for different cultures. For example, a study involving six European countries - the United Kingdom, Sweden, the Netherlands, Luxembourg, Austria, and Italy - showed that self-esteem was significantly associated with life satisfaction on elderly people. Similar results have been found among elderly people in China, Poland and Germany. In addition, several studies have shown that loneliness is negatively associated with self-esteem[49–53].  found that people with a high level of loneliness tended to report lower levels of self-esteem. (Çivitci et al., 2009) found that self-esteem can mediate the relationship between loneliness and life satisfaction. In China, due to the "family continuity" complex embedded in traditional culture, grandparents usually regard grandparenting as their responsibilities and an expression of self-worth in later life. A study of 429 Chinese older people found that intergenerational support was associated with life satisfaction, with loneliness and self-esteem playing a partially mediating role. Thus, we speculate that self-esteem may be another important mediator in the relationship between intergenerational care and life satisfaction.
1.3 The current study
From what has been discussed above, we can find that there might be some relationships between grandparenting, loneliness, self-esteem and life satisfaction among elderly people. In addition, loneliness and self-esteem may play crucial roles between grandparenting and life satisfaction. However, few studies have paid attention to elderly migrants who face the dual threat of aging and migration. This study aims to examine whether these relationships also exist in elderly migrants. To answer this question, we implemented this study and proposed the following four hypotheses:
Grandparenting was positively correlated with life satisfaction among elderly migrants.
Loneliness played a mediating role between grandparenting and life satisfaction among elderly migrants.
Self-esteem played a mediating role between grandparenting and life satisfaction among elderly migrants.
Loneliness and self-esteem co-played a serial mediating role between grandparenting and life satisfaction among elderly migrants.