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Background: Physical activity (PA) is generally encouraged. Studies from developed countries in the West have shown that maintenance of ade-quate PA or increasing PA are associated with lower mortality risk. It is unclear whether these associations apply to an older Chinese population. Hence, we examined the changes in PA prospectively among a middle-aged and older Chinese population over an average of 4 years and explored their subsequent mortality risks. Methods: Metabolic equivalent scores of PA among participants in the Guangzhou Biobank Cohort Study were calculated. Participants were divided into 3 groups related to PA level, and changes in PA were classified into 9 categories. Information on vital status and causes of death from March 2008 to December 2012 (the first repeated examination) until December 31, 2017, was obtained via record linkage with the Death Registry. Results: Of 18,104 participants aged 61.21 ± 6.85 years (mean ± SD), 1461 deaths occurred within 141,417 person-years. Compared to partici-pants who maintained moderate PA, those who decreased PA from moderate or high levels to a low level had increased risks for all-cause mortal-ity (hazard ratio (HR)=1.47, 95% confidence interval (95%CI): 1.11-1.96). Participants who maintained a high level of PA (HR=0.83, 95%CI:0.70-0.98) or increased PA from low to high levels (HR=0.71, 95%CI: 0.52-0.97) showed lower all-cause mortality risks. Those who main-tained low PA levels showed a higher all-cause mortality risk, whereas those who increased their PA levels showed a non-significantly lower risk. Similar results were found for cardiovascular disease risk. Conclusion: Even at an older age, maintaining a high PA level or increasing PA from low to high levels results in lower mortality risks, suggest-ing that substantial health benefits might be achieved by maintaining or increasing engagement in adequate levels of PA. The increased risk of maintaining a low PA level or decreasing PA to a low level warrants the attention of public health officials and clinicians.