Brain blood flow reduction associated with kidney function
Brain health requires adequate cerebral blood flow. A study just published in the Journal of the American Society of Nephrology demonstrates that impairments in kidney function consistent with mild CKD (chronic kidney disease) are associated with reduced blood flow in the brain. The authors state:
"CKD is linked with various brain disorders. Whereas brain integrity is dependent on cerebral perfusion, the association between kidney function and cerebral blood flow has yet to be determined."
So they examined data from the population–based Rotterdam Study that included 2645 participants with an average age of 56.6 years, roughly half men and women. They used eGFR (calculated rate of kidney filtration) and the albumin-to-creatinine ratio to assess kidney function and phase–contrast magnetic resonance imaging of the basilar and carotid arteries to measure cerebral blood flow. The albumin-to-creatinine ratio didn't pan out when subjected to adjustment for cardiovascular risk factors, but every decrease in eGFR was associated with reduced brain blood flow:
"Participants had an average (SD) eGFR of 86.3 (13.4) ml/min per 1.73 m2 and a median (interquartile range) albumin-to-creatinine ratio of 3.4 (2.2–6.1) mg/g. In age- and sex-adjusted models, a higher albumin-to-creatinine ratio was associated with lower cerebral blood flow level (difference in cerebral blood flow [milliliters per minute per 100 ml] per doubling of the albumin-to-creatinine ratio, −0.31... The association was not present after adjustment for cardiovascular risk factors (P=0.10). Each 1 SD lower eGFR was associated with 0.42 ml/min per 100 ml lower cerebral blood flow (95% confidence interval, 0.01 to 0.83) adjusted for cardiovascular risk factors."
Implications for blood pressure management
This applies to the general population without overt kidney disease, and clinicians should bear in mind the importance of maintaining adequate cerebral blood flow when managing hypertension and the evidence documenting worse outcomes when blood pressure is medicated too aggressively. According to the authors' conclusion, even mild CKD may heighten the risk of adverse events such as cognitive impairment, falls and dizziness due to impairments of brain perfusion when blood pressure is forced too low.
"Thus, in this population-based study, we observed that lower eGFR is independently associated with lower cerebral blood flow."