Breaks in Sedentary Time, Brain Health, and Cognitive Function in Rural-Dwelling Older Adults: A Population-Based Study

Background: To examine associations of accelerometer-measured sedentary parameters with structural brain markers and cognitive function, and further to explore the mediation role of brain markers in the associations between sedentary parameters and cognitive function.Methods: This population-based study included 2019 rural-dwelling older adults (age ≥60 years, 59% women) who were free of dementia derived from the baseline participants of MIND-China. In 2018-2020, we used an accelerometer to assess sedentary parameters (e.g., uninterrupted bouts and breaks) and a neuropsychological test battery for cognitive function. In a subsample (n=1009), structural brain markers were assessed on 3T brain MRI. Data were analyzed using the general linear, isotemporal substitution, and mediation models.Findings: In the total sample, adjusting for multiple confounders and moderate-to-vigorous physical activity, longer mean sedentary bout duration was linearly associated with lower z-scores of global cognition, memory, and verbal fluency (P<0.05), whereas the linear association of greater total sedentary time with poorer global cognition, memory, and verbal fluency existed only among older adults with long sedentary time (>10 hours/day) (P<0.05); Replacing sedentary time with the same amount of LPA was significantly associated with higher memory and verbal fluency z-scores (P<0.05). In the MRI subsample, simultaneously or separately entering multiple structural brain markers into the mediation models substantially attenuated the associations between mean sedentary bout duration and cognitive z-scores.Interpretation: Prolonged uninterrupted sedentary time is associated with poor global cognition, memory, and verbal fluency among rural-dwelling older adults, in which the association is partially mediated by structural brain markers. Trial Registration Details: MIND-China was registered in the Chinese Clinical Trial Registry (registration no.: ChiCTR1800017758).Funding Information: This work was supported in part by grants from the National Natural Science Foundation of China (grants no.: 82171175, 81861138008, and 81772448), the Alzheimer’s Association Grant (grant no.: AACSFD-22-922844), the National Key R&D Program of China Ministry of Sciences and Technology (grant no.: 2017YFC1310100), the Natural Science Foundation of Shandong Province (grant no.: ZR2021MH005), the Academic Promotion Program of Shandong First Medical University (2019QL020), the Integrated Traditional Chinese and Western Medicine Program in Shandong Province (YXH2019ZXY008), and the Brain Science and Brain-like Intelligence Technology Research Projects of China (2021ZD0201801 and 2021ZD0201808). CQ received grants from the Swedish Research Council (grants no.: 2017-05819 and 2020-01574), the Swedish Foundation for International Cooperation in Research and Higher Education (grant no.: CH2019-8320), and Karolinska Institutet, Stockholm, Sweden. LJL is supported by the Intramural Research Program, National Institute on Aging, Maryland, USA.Declaration of Interests: The authors declare no financial or other conflicts of interest.Ethics Approval Statement: The Ethics Committee of Shandong Provincial Hospital approved the MIND-China protocol. Written informed consent was obtained from all participants.