Lowering blood pressure does not lead to kidney damage
In contrast to previous reports, scientists have determined, upon further research, that intensive blood pressure control does not lead to kidney injury in people who do not have chronic kidney disease (CKD). Elevated blood pressure is relatively common in the U.S. population and is a risk factor for heart disease, stroke, and CKD. The Systolic Blood Pressure Intervention Trial (SPRINT) was designed to test whether using medications to reduce systolic blood pressure to a lower goal than currently recommended would reduce cardiovascular disease in people with high blood pressure but not diabetes. (“Systolic” refers to the higher of the two numbers in a blood pressure reading; it measures the pressure in the arteries when the heart beats. “Diastolic” refers to the lower of the two numbers and measures the blood pressure when the heart rests between beats).
SPRINT researchers previously reported that, among the subset of study participants who did not have CKD at the start of the trial, those who received an intensive blood pressure control regimen were at a slightly higher risk of developing CKD than those who received standard care. They defined new-onset CKD as a minimum 30 percent reduction in the rate at which kidneys filter blood (filtration rate), to a level considered less than normal. This elevated CKD risk was generally outweighed by a reduced likelihood of cardiovascular events and death. However, because kidney filtration rates are dependent on blood pressure, the observed reduction in kidney function in these participants could simply reflect changes in blood flow, not necessarily underlying kidney damage. To explore this possibility, SPRINT researchers tested urine samples from study participants for the presence of several molecules known to be directly associated with various types of kidney damage (also known as “biomarkers” of kidney damage). Surprisingly, after 1 year of intensive blood pressure control, participants who developed CKD exhibited greater reductions in some urinary biomarkers of kidney damage than those who did not develop CKD. In addition, urine from study participants who did not receive intensive blood pressure control but nonetheless developed CKD had elevated kidney damage biomarkers compared with those who received the intensive blood pressure regimen. These results suggest that a blood flow effect, rather than a bona fide kidney injury, led to the mis-classification of CKD in these study participants. Patients and clinicians are now empowered by this new information to seek more intensive blood pressure control to reduce the risk of mortality.
Zhang WR, Kraven TE, Malhotra R,…Ix JH.; for the SPRINT Research Group. Kidney damage biomarkers and incident chronic kidney disease during blood pressure reduction. Ann Intern Med 169: 610-618, 2018.