AbstractIntroductionDecreased renal function is a potential risk factor for dementia.MethodsThis retrospective cohort study of 2.8 million adults aged ≥50 years used the IMRD‐THIN database, representative of UK primary care, from January 1, 1995 to February 24, 2020. The associations between estimated glomerular filtration rate (eGFR) and urine albumin creatinine ratio (ACR) with incident all‐cause dementia were analyzed using Cox regression.ResultsIn the eGFR cohort (n = 2,797,384), worsening renal dysfunction was associated with increased hazard of all‐cause dementia, with greatest hazard at eGFR 15–30 ml/min/1.73min² (hazard ratio [HR] 1.26, 95% confidence interval [CI] 1.19–1.33). In the ACR cohort (n = 641,912), the hazard of dementia increased from ACR 3–30 mg/mmol (HR 1.13, 95% CI 1.10–1.15) to ACR > 30 mg/mmol (HR 1.25, 95% CI 1.18–1.33).DiscussionWorsening eGFR and albuminuria have graded associations with the risk of dementia, which may have significant implications for the care of patients with kidney disease.