Trends in cognitive function before and after diabetes onset in China

Abstract Background Individuals with prevalent diabetes were reported to have higher risk of dementia and lower cognitive function. However, the trends of cognitive function before diabetes and in the years following diabetes onset remain unclear. Methods and Findings This study included 12422 participants aged >45 years without baseline diabetes from the China Health and Retirement Longitudinal Study (CHARLS). Cognitive function was assessed at baseline (Wave 1, 2011), and at least one time from Wave 2 (2013) to Wave 4 (2018). During the 7-year follow-up, 1207 (9.7%, 59.1 ± 8.6 years, 39.9% males) participants developed new-onset diabetes. The cognitive function of both the without-diabetes group and the diabetes group declined annually during the follow-up. The annual decline rate of the diabetes group before diabetes onset was similar to that of the without-diabetes group during the follow-up. After diabetes onset, participants experienced accelerated rates of cognitive decline in global cognition (β, −0.023 SD/year; 95% CI, −0.043 to −0.004) and visuospatial abilities (−0.036 SD/year; −0.061 to −0.011), but not in orientation abilities (0.001 SD/year; −0.018 to 0.020). We also observed a tendency that episodic memory (−0.018 SD/year; −0.041 to 0.004) and attention and calculation abilities (−0.017 SD/year; −0.037 to 0.003) declined faster after new-onset diabetes, although the results did not meet our threshold of significance. In subgroup analysis, compared with those who developed diabetes between 45–54 years old, those developing diabetes older showed similar increments in cognitive decline rate after diabetes. Conclusions Individuals experienced faster rate of cognitive decline after diabetes onset, but not during the pre-diabetes period. Age did not modify the effect of diabetes on future cognitive decline. Future studies are needed to learn the mechanisms of cognitive decline in a few years after new-onset diabetes.