INTRODUCTION: China has the world's largest number of older adults with cognitive impairment (CI). We aimed to examine secular trends in the prevalence of CI in China from 2002 to 2018.

METHODS: Generalized estimating equations (GEE) was used to assess changes in CI trend in 44,154 individuals (72,027 observations) aged 65 to 105 years old.

RESULTS: The prevalence of CI increased from 2002 to 2008 and then decreased until 2018. The age-standardized prevalence increased from 25.7% in 2002, 26.1% in 2005, to 28.2% in 2008, then decreased to 26.0% in 2011, 25.3% in 2014, and 24.9% in 2018. Females and those ≥ 80 years old had greater CI prevalence.

DISCUSSION: The prevalence of CI showed an inverted U shape from early 2000s to late 2010s with a peak in 2008. Follow-up studies are needed to confirm the decreasing trend after 2008 and examine the contributing factors and underlying mechanisms of this trend.