Kidney disease and risk of dementia: a Danish nationwide cohort study

OBJECTIVES: It is unclear whether kidney disease is a risk factor for developing dementia. We examined the association between kidney disease and risk of future dementia. DESIGN AND SETTING: Nationwide historical registry-based cohort study in Denmark based on data from 1 January 1995 until 31 December 2016. PARTICIPANTS: All patients diagnosed with kidney disease and matched general population cohort without kidney disease (matched 1:5 on age, sex and year of kidney disease diagnosis). PRIMARY AND SECONDARY OUTCOME MEASURES: All-cause dementia and its subtypes: Alzheimer’s disease, vascular dementia and other specified or unspecified dementia. We computed 5-year cumulative incidences (risk) and hazard ratios (HRs) for outcomes using Cox regression analyses. RESULTS: The study cohort comprised 82 690 patients with kidney disease and 413 405 individuals from the general population. Five-year and ten-year mortality rates were twice as high in patients with kidney disease compared with the general population. The 5-year risk for all-cause dementia was 2.90% (95% confidence interval: 2.78% to 3.08%) in patients with kidney disease and 2.98% (2.92% to 3.04%) in the general population. Compared with the general population, the adjusted HRs for all-cause dementia in patients with kidney disease were 1.06 (1.00 to 1.12) for the 5-year follow-up and 1.08 (1.03 to 1.12) for the entire study period. Risk estimates for dementia subtypes differed substantially and were lower for Alzheimer’s disease and higher for vascular dementia. CONCLUSIONS: Patients diagnosed with kidney disease have a modestly increased rate of dementia, mainly driven by vascular dementia. Moreover, patients with kidney disease may be underdiagnosed with dementia due to high mortality and other comorbidities of higher priority.