Age at Diabetes Diagnosis and Cognitive Function Among Older Adults in the China Health and Retirement Longitudinal Study, 2011–2018

Background This study examines the dynamic relationship between age at diabetes diagnosis and cognitive function in middle-aged and elderly Chinese adults using longitudinal data (2011–2018) from the China Health and Retirement Longitudinal Study (CHARLS). Methods A total of 39,110 participants aged ≥ 45 years were included in the analysis. Generalized linear mixed models (GLMM) were employed to assess relationships between diagnostic age groups (45–59 years, 60–74 years, ≥ 75 years) and standardized cognitive scores. Results At baseline, individuals with diabetes demonstrated significantly higher cognitive scores than non-diabetic individuals (12.71 ± 3.25 vs. 12.48 ± 3.26; p < 0.001), with diabetes status showing a modest protective effect (β = 0.127; p = 0.022). Age stratification revealed substantial heterogeneity in this association: diabetes was positively correlated with cognitive scores in participants under 60 years, while accelerated cognitive decline was observed in the ≥ 75-year group. Longitudinal trajectories diverged significantly over time - diabetic patients experienced progressive cognitive decline, whereas non-diabetic individuals showed steady improvement. This trend narrowed the between-group difference in cognitive scores from 0.23 points in 2011 to 0.05 points in 2018. Conclusion Diabetes manifests a dual impact on cognitive function in China’s elderly population, characterized by short-term protection effects but long-term impairment. Age at diagnosis critically determines the direction of this association, providing crucial evidence for the development of age-stratified strategies for cognitive health management in diabetic populations.