Background <p>Cardiovascular–kidney–metabolic (CKM) syndrome is increasingly linked to cognitive impairment, yet its association with cognitive trajectories at early stages remains unclear in Chinese adults.</p> Methods <p>We analyzed 6,982 adults (≥ 45 years) without baseline clinical cardiovascular disease from the China Health and Retirement Longitudinal Study. Participants were classified into early CKM stages (0–3). Cognitive trajectories (standardized z-scores) over 7 years were evaluated using linear mixed-effects models. Cox proportional hazards models assessed the risk of substantial cognitive decline (≥ 1 SD decrease from baseline).</p> Results <p>Individuals in stage 3 showed significantly lower baseline cognitive scores than those in stage 0. All groups experienced cognitive decline during follow-up, but decline was faster in stage 3, whereas stages 1–2 showed trajectories similar to stage 0. Stage 3 was also associated with a higher, borderline significant risk of substantial cognitive decline after adjustment for demographic, behavioral, and clinical factors.</p> Conclusions <p>CKM stage 3 was associated with poorer cognitive performance and accelerated cognitive decline. Early identification and comprehensive management of CKM syndrome may help preserve cognitive health.</p>