AUTHOR=Sun Xueshan , Sun Danyi , Zhou Zhongliang , Lu Jiao 
  
TITLE=Joint trajectories of online and offline social activity, cognitive decline, and frailty progression among middle-aged and older adults in China
  
JOURNAL=International Journal of Public Health
  
VOLUME=Volume 71 - 2026
  
YEAR=2026
  
URL=https://www.ssph-journal.org/journals/international-journal-of-public-health/articles/10.3389/ijph.2026.1610116
  
DOI=10.3389/ijph.2026.1610116
  
ISSN=1661-8564
  
ABSTRACT=ObjectivesTo identify joint trajectories of online and offline social activity and examine their associations with cognitive decline and frailty progression among middle-aged and older adults in China.MethodsData from 14,340 adults aged ≥45 years in CHARLS (2011–2018) were analyzed; outcome-specific samples included 10,323 participants for cognition and 13,960 for frailty. Group-based multi-trajectory modeling identified trajectories. Linear mixed-effects models estimated associations with annual changes in cognition and frailty.ResultsThree trajectories were identified: persistently low social activity engagement (G1, 47.8%), offline social activity dominant (G2, 47.0%), and online social activity increasing (G3, 5.2%). Compared with G1, G2 showed slower cognitive decline (0.010 SD units/year, 95% CI [0.002, 0.018]) and frailty progression (−0.014 SD units/year, 95% CI [−0.020, −0.007]); G3 showed stronger associations for cognition (0.044 SD units/year, 95% CI [0.029, 0.060]) and frailty (−0.041 SD units/year, 95% CI [−0.055, −0.026]).ConclusionThe Offline Social Activity Dominant Group was associated with slower cognitive decline and frailty progression, with stronger associations for the Online Social Activity Increasing Group. Integrating online and offline social participation may support healthy aging.