## 4 Results
### Influencing Factors of the Change in Life Expectancy
#### 4.4.3 Natural Environment  
The average altitude is significantly positively related to the change in life expectancy overall. The higher the average altitude, the greater the growth of life expectancy because the areas with higher altitude are mostly mountainous areas with a lower initial level of life expectancy, so there is more room for growth. The regression coefficient decreases gradually from the eastern coast to the inland, indicating that for the same altitude, the increase in life expectancy in the east is greater than that in central and west China, indicating that economic development can compensate for the restriction of natural conditions on the improvement of life expectancy (accessibility of transportation and availability of medical facilities). This also reminds us that in order to narrow the gap in health development among regions and to realize Healthy China 2030, we need to focus on improving life expectancy and vigorously developing the economy in the western region, especially in the mountainous areas (Figure 5).  
The impact of air quality on the change in life expectancy illustrates a significant East-West difference, with a negative impact in the East and a positive impact in the West. The worse the air quality in the East, the smaller the increase in life expectancy, which is basically consistent with common sense [40]. Rapid economic development in eastern China has had a significant negative impact on the environment; at the same time, a fast pace of life, increased psychological stress and anxiety driven by rapid economic development are also not conducive to health improvement. However, the economic development level in western China is relatively low. The positive effects of rapid urbanization on health may exceed the negative effects mentioned above, which is conducive to health improvement overall. This suggests that different measures for improvement of the health status should be taken in regions at different stages of economic development, such as paying more attention to people's living environments and mental health in economically developed areas, while the key measure to improving overall life expectancy is to improve the level of economic development in underdeveloped areas.  
Figure 5: _Cont_.  
The average slope is positively connected with the change in life expectancy except for the Northeast China. This is because the areas with higher slopes are mostly mountainous areas with lower initial levels of life expectancy, so there is more room for growth. The regression coefficient shows a gradual increase trend from east to west, indicating that for the same slope, the increase in life expectancy in the western region is greater. Since development of the western region in China began, investment in funds and preferential policies for this region have been strengthened. In addition, its urban and rural medical and health system has gradually been fully covered, health resources have been fully utilized, the health service level (maternal and child health care) has been significantly improved, and the health service level is increased.  
Figure 5: Regression results of the GWR model: (**a**) Average altitude (ln); (**b**) Average level of air quality for many years; (**c**) Average slope; (**d**) Perennial mean temperature.  
considerable progress has been made in medical and health services, and people's health conditions have continuously improved.  
The impact of temperature on the change in life expectancy illustrates a significant south-north difference, indicating that the higher the temperature in the south, the smaller the increase in life expectancy; and the higher the temperature in the north, the greater the increase in life expectancy, especially in Northeast China. This may have a significant relationship with the initial temperature level. The perennial mean temperature in Northeast China is generally low, and with the increase in temperature, it is beneficial to health.