Association of Environmental Factors and Aging Levels Under Different Urbanization Levels in China

In China, the processes of population aging and urbanization are persistently accelerating. To gain insights into the association of environmental factors and aging levels under different urbanization levels, this study examined how these factors correlate with aging levels across varying degrees of urbanization in China. County-level data encompassing aging levels and 22 pertinent factors were collated for the years 2010 and 2020. Aging levels were quantified by the proportions of elderly population aged 65+ and 85+ within the total population. The counties were categorized into three urbanization levels: high, medium, and low. Fixed effect models and random forest models were established to scrutinize the impacts and significance of independent variables on aging levels under different urbanization levels. Notably, the aging levels across all urbanization levels rose by a factor of 1.5-2.1 from 2010 to 2020. The results of the two models indicate that there are urbanization gradient differences in the impact factors: in low-urbanization areas, resident savings and PM_2.5 are the important variables; in medium-urbanization counties, resident savings and air pollution such as CO, SO₂, PM_2.5, and O₃ are the important variables; in high-urbanization counties, climate factors such as average temperature in January and July are the important variables. Moreover, air pollutants show age-specific associations, and medical resources only have a significant supporting impact on LA85+. The study reveals the transformation rule of the aging driving mechanism in the urbanization process from "economic foundation support" to "life quality adaptation," providing a scientific basis for formulating differentiated health aging policies.