Based on the panel data of China's prefecture-level cities in 2000, 2010, and 2020, this paper examines the spatial effects of population ageing on technological innovation and explores the heterogeneous impacts of ageing on technological innovation at different stages of social and economic development. The analytical results of the spatial Durbin model exhibit a robust inverted U-shaped relationship between population ageing and local technological innovation, as well as a U-shaped relationship between population ageing and neighbors' innovation. Furthermore, the threshold regression models indicate that, at the stage of low urbanization rate and insufficient supply of health services, population ageing imposes a significantly negative impact on technological innovation. With higher urbanization and a more adequate supply of health services, population ageing would stimulate innovation. Therefore, against the backdrop of the irreversible ageing process, promoting the urbanization process and improving the health care system will effectively attenuate the discouraging effects of ageing on innovation.

Using the data of 2014 baseline survey of the China Longitudinal Ageing Social Survey (CLASS), which provides a sample of Chinese older adults who have grandchild younger than 18 years old, this study examines the associations among grandchild care, social networks, and depressive symptoms among Chinese older adults. The older adults are divided into three groups basing on the frequency of grandchild care provision, including ‘no care’,‘providing care occasionally’ and ‘providing care frequently’ respectively. The mediating and moderating effects of social networks between grandchild care and depressive symptoms are tested. Results show that older adults who provide grandchild care report larger social networks and better mental health than those who dont provide grandchild (reference group). After controlling other variables, the older adults who provide grandchild care occasionally benefit more than those who take care of grandchild frequently. Grandchild care is related to larger social networks, and the association between grandchild care and depressive symptoms is fully mediated by social networks.