Association between different dementia diagnosis and kidney function decline: A Swedish registry study

Abstract Background Population studies have shown that chronic kidney disease(CKD) and CKD progression are associated with dementia, particularly Alzheimer’s dementia(AD) and vascular dementia(VD). However, the impact of different brain pathogenesis on these associations is not known. Method Observational study of patients with recently diagnosed dementia disorders from the Swedish Dementia Registry(SveDem) 2007‐2018 linked with complete information of kidney function tests [estimated glomerular filtration rate(eGFR)] over time from the Stockholm CREAtinine Measurements(SCREAM) registry. The study exposure were different dementia diagnosis [AD, VD, mixed dementia, dementia with Lewy Bodies(DLB) and Parkinson’s disease dementia(PDD), frontotemporal dementia(FTD), unspecified dementia(UNS) and other dementia types]. The study outcome was CKD progression, defined as the composite of a sustained eGFR decline of>30% from baseline, initiation of kidney replacement therapy or death attributed to kidney disease. We performed competing risk analyses where death from non‐renal causes was considered as competing events for CKD progression. Confounders included demographics, comorbidities, and baseline kidney function. Result We included 20,618 patients, of whom, 6,452(31%) had AD, 7,012(34%) had mixed dementia, 3,987(19%) had VD, 764(4%) had DLB or PDD, 312(2%) had FTD, and 2,091(10%) patients were diagnosed with unspecified or other dementia diagnoses. The mean age was 80 years (60%female). During median follow‐up time of 2.5 (IQR1.0‐4.5) years, 2,225(11%) events of CKD progression occurred, along with 8,684(42%) non‐renal deaths. After adjusting for confounders and accounting for competing risks, a higher risk of CKD progression compared to patients with AD was observed for patients with VD [sub‐HR, 95%CI 1.19;1.05‐1.34], mixed (1.13;1.02‐1.26), UNS or other dementia types (1.13;0.96‐1.32), while patients with DLB or PDD dementia had 46% lower risk of CKD progression (0.54;0.39‐0.76), and those with FTD showed no difference compared to AD (0.99;0.64‐1.51). Conclusion VD and mixed dementia (vs AD diagnosis) were associated with a higher risk of CKD progression, whereas DLB or PDD dementia were associated with lower risk of CKD progression. Since DLB and PDD dementia involve less and VD and mixed dementia more vascular pathology, this suggests that vascular mechanisms may play an important role in the brain‐kidney axis. Future studies are needed to explore this hypothesis.