The global health burden of chronic kidney disease is rapidly rising, and chronic kidney disease is an important risk factor for cerebrovascular disease. Proposed underlying mechanisms for this relationship include shared traditional risk factors such as hypertension and diabetes, uremia-related nontraditional risk factors, such as oxidative stress and abnormal calcium-phosphorus metabolism, and dialysis-specific factors such as cerebral hypoperfusion and changes in cardiac structure. Chronic kidney disease frequently complicates routine stroke risk prediction, diagnosis, management, and prevention. It is also associated with worse stroke severity, outcomes and a high burden of silent cerebrovascular disease, and vascular cognitive impairment. Here, we present a summary of the epidemiology, pathophysiology, diagnosis, and treatment of cerebrovascular disease in chronic kidney disease from the Kidney Disease: Improving Global Outcomes Controversies Conference on central and peripheral arterial disease with a focus on knowledge gaps, areas of controversy, and priorities for research.

Chronic kidney disease (CKD) has a rapidly rising global prevalence, affecting as many as one-third of the population over the age of 75 years. CKD is a well-known risk factor for cardiovascular disease and, in particular, there is a strong association with stroke. Cohort studies and trials indicate that reduced glomerular filtration rate increases the risk of stroke by about 40% and that proteinuria increases the risk by about 70%. In addition, CKD is also strongly associated with subclinical cerebrovascular abnormalities, vascular cognitive impairment and dementia. The mechanisms responsible for these associations are currently unclear. CKD is associated with traditional risk factors such as hypertension, diabetes mellitus and atrial fibrillation, but non-traditional risk factors such as uraemia, oxidative stress, mineral and bone abnormalities, and dialysis-related factors, such as changes in cerebral blood flow or cardiac structure, are also postulated to play a role. Kidney disease can also impact and complicate the treatments used in acute stroke and in secondary prevention. In this review, we will outline our current understanding of the epidemiology and pathophysiology of cerebrovascular disease in CKD.

Hypertension affects more than one in four adults. The brain is an early target of hypertension-induced organ damage, and may manifest as stroke, subclinical cerebrovascular abnormalities and dementia. Hypertension-related small vessel disease can cause vascular dementia and can potentiate Alzheimer’s pathology, lowering the threshold at which signs and symptoms manifest. Many hypertensive emergencies may also have a neurological presentation, such as hypertensive encephalopathy, haemorrhagic stroke or pre-eclampsia. Here we highlight the importance of blood pressure in maintaining brain health and the brain’s role in controlling blood pressure.

Background and Objectives: Chronic kidney disease (CKD) increases the risk of stroke, but the extent through which this association is mediated by hypertension is unknown. We leveraged large-scale genetic data to explore causal relationships between CKD, hypertension and cerebrovascular disease phenotypes. Methods: We used data from genome-wide association studies (GWAS) of European ancestry to identify genetic proxies for kidney function (CKD diagnosis, estimated glomerular filtration rate [eGFR], and urinary albumin-to-creatinine ratio [UACR]), systolic blood pressure (SBP), and cerebrovascular disease (ischaemic stroke and its subtypes, and intracerebral haemorrhage [ICH). We then conducted univariable, multivariable and mediation Mendelian randomization (MR) analyses to investigate the effect of kidney function on stroke risk and the proportion of this effect mediated through hypertension. Results: Univariable Mendelian randomization revealed associations between genetically determined lower eGFR and risk of all stroke (OR per 1-log decrement in eGFR, 1.77; 95% CI, 1.31-2.40; p<0.001), ischaemic stroke (OR, 1.81; 95% CI, 1.31-2.51; p<0.001), and most strongly with large artery stroke (LAS) (OR, 3.00; 95% CI, 1.33-6.75; p=0.008). These associations remained significant in the multivariable MR analysis, controlling for SBP (OR, 1.98; 95% CI, 1.39-2.82; p<0.001 for AS; OR, 2.16; 95% CI, 1.48-3.17; p<0.001 for IS; OR, 4.35; 95% CI, 1.84-10.27; p=0.001 for LAS), with only a small proportion of the total effects mediated by SBP (6.5% [0.7-16.8%], 6.6% [0.8-18.3%] and 7.2% [0.5-24.8%], respectively). Total, direct and indirect effect estimates were similar across a number of sensitivity analyses (Weighted median, MR-Egger regression). Discussion: Our results demonstrate an independent causal effect of impaired kidney function, as assessed by decreased eGFR, on stroke risk, particularly LAS, even when controlled for SBP. Targeted prevention of kidney disease could lower atherosclerotic stroke risk independent of hypertension.

Background: Proteinuria has emerged as an important vascular risk factor for adverse cardiovascular events including stroke. Hypertension has been proposed as the principal confounder of this relationship but its role has not been systematically examined. Aim: We aimed to determine if proteinuria remains an independent predictor of stroke after more complete adjustment for blood pressure. Summary of review: We performed a systematic review, searching MEDLINE and EMBASE (to February 2018) for cohort studies or randomized controlled trials that reported stroke incidence in adults according to baseline proteinuria ± glomerular filtration rate. Study and participant characteristics and relative risks were extracted. Estimates were combined using a random effects model. Heterogeneity was assessed by χ ² statistics and I², and by subgroup strata and meta-regression, with a particular focus on the impact of more complete adjustment for blood pressure on the association. The quality of cohort studies and post hoc analyses was assessed using the Newcastle–Ottawa Scale. We identified 38 studies comprising 1,735,390 participants with 26,405 stroke events. Overall, the presence of any level of proteinuria was associated with greater stroke risk (18 studies; pooled crude relative risk 2.00, 95%CI 1.63–2.46; p < 0.001) even after adjustment for established cardiovascular risk factors (33 studies; pooled adjusted relative risk 1.72, 1.51–1.95; p < 0.001), albeit with considerable heterogeneity between studies (p < 0.001; I²= 77.3%). Moreover, the association did not substantially attenuate with more thorough adjustment for hypertension: single baseline blood pressure measure (10 studies; pooled adjusted relative risk = 1.92, 1.39–2.66; p < 0.001); history or treated hypertension (four studies; pooled adjusted relative risk = 1.76, 1.13–2.75, p = 0.013); multiple blood pressure measurements over months to years (four studies; relative risk = 1.68, 1.33–2.14; p < 0.001). Conclusions: Even after extensive adjustment for hypertension, proteinuria is strongly and independently associated with incident stroke risk, possibly indicating a shared renal and cerebral susceptibility to vascular injury that is not fully explained by traditional vascular risk factors.