We observed that rural-to-urban elderly female (but not male) migrants exhibited a better cognition level than their non-migrant counterparts. These differences were evident in the overall level of cognitive function but not the rate of cognitive decline, and were partly explained by variations in psychosocial factors. This work indicated the direction of specific interventions for internal elderly migrants, and revealed the population that require more attention.
In our study, the difference in the rate of cognitive decline between migrants and non-migrants was not significant, and this finding might be explained by the following reasons. First, given the fact the both rural-to-urban migrants and rural non-migrants had rural life experiences, differences in the rates of cognitive decline between rural-to-urban migrants and rural non-migrants were not as significant as those observed between rural and urban residents [18]. Second, the effects of rural-to-urban migration on cognitive function may involve a slow and complex process that might not be detectable in the relatively short four-year follow-up period of CHARLS. According to Cattell’s categorization of cognitive abilities, cognition can be divided into two dimensions, namely fluid and crystallized abilities [29]. Some researchers claimed that fluid abilities, such as memory, tend to decline linearly from early adulthood and are more difficult to improve or otherwise change in older adults [30, 31]. This was consistent with our observation that the effect of migration on episodic memory was not significant.
Our results confirmed that more than half of rural-to-urban migrants lived with their adult children, suggesting that the older adults had moved to follow their adult children. And we observed that living with children was associated with a worse cognitive function performance, indicating that some elderly individuals who were disabled or could not perform self-care may have moved to the cities to receive help from their adult children. However, our results also revealed that some older adults may have migrated to provide help (e.g., voluntary care of grandchildren) to their adult children.
Although both female and male migrants were more likely to provide intergenerational care than non-migrants, according our findings, this activity only provided cognitive benefits in terms of the mental status among female migrants. Previous studies claimed that providing voluntary care to grandchildren might have a positive effect on the elderly caregiver’s cognitive function by enhancing the caregiver’s senses of self-esteem and self-worth and providing a new purpose in later life [32–34]. However, this effect may be somewhat sex-specific and more benefit female caregiver [13, 14]. Our study yielded similar results, this outcome may be partly attributable to traditional social norms in China, where women are typically expected to be responsible for domestic affairs and family life, play a nurturing role and serve as kin-keepers, whereas men are expected to fulfil the role of breadwinner. Accordingly, grandfathers who migrate to urban areas specifically to provide care for grandchildren would deviate from this traditional social norm. Therefore, female rural-to-urban elderly migrants would more easily benefit from caring for grandchildren.
Our findings also suggested other explanations regarding the sex-specific difference in cognitive function between migrants and non-migrants. We observed that female elderly migrants performed better in terms of social attachment than female non-migrants, particularly in leisure activities. This finding was inconsistent with those of previous studies, which reported problem of poor social adaptation and integration faced by migrants [6, 20, 35]. This inconsistency may be related to the selection of the control group, which comprised non-migrant rural elderly in our study, however, local citizens in other studies. Compared with rural areas, urban areas feature a wealth of community activities and facilities for leisure activities [36, 37], which provide migrants with more opportunities for participation. Consequently, rural-to-urban migrants had more opportunities for leisure activities. However, increased participation in leisure activities was only observed in female migrants. This may be explained by following reasons, compared to men, women tend to have more larger and varied social networks and to exchange support with a greater number of members in their networks [38]. In contrast, men often depend solely on their spouses and may be less likely to participate in social activities in the community [39].
Our study has some limitations that should be acknowledged. First, although we used the Hukou status to classify participants into rural and urban populations, in accordance with the Chinese special background and previous research [37, 40, 41], detailed information about migration, such as the migration time, process and reasons, were not available. Further studies should be conducted based on different reasons for migration. Second, it was difficult to match rural-to-urban migrants with rural non-migrants who shared same residential location information in Hukou. Given the significant development gap between different regions of China, it would be more reasonable to compare populations from the same region. Third, although this analysis covered a four-year period, this might not have been sufficient to enable the development of differences in the rates of cognitive decline. Fourth, rural-to-urban migration was associated with the level of cognitive function performance, but not the rate of cognitive decline. Although possible confounders were adjusted, reverse causation may have existed within those relationships. Further studies are needed to investigate the mechanisms underlying those associations.