For a long time, the control of blood pressure in patients with chronic kidney disease (CKD) has been strict.
The United States 2014 adult hypertension evidence-based management guidelines recommend that the blood pressure of adults under 60 years old and CKD patients of all ages should be controlled below 140/90mmHg, and those without CKD over 60 years old should be controlled below 150/90mmHg. KDIGO guidelines recommend that the blood pressure of CKD patients of all ages be controlled below 140/90mmHg, and that proteinuria patients be controlled below 130/80mmHg. Other guidelines recommend that specific complications such as diabetes or target organ damage should be controlled below 130/80mmHg.
However, there is a lot of evidence that strict control of blood pressure is not completely beneficial to CKD.
Nearly half of adult CKD patients are over 70 years old. A study that suggested that controlling blood pressure could reduce mortality, cardiovascular disease and stroke in the elderly also only controlled the systolic blood pressure below 160 mmHg, and supported that it was safe to control the systolic blood pressure of CKD patients at 130 mmHg, which did not include more than 70 elderly people.
Kovesdy et al. recently reviewed a group of CKD veterans and found a nonlinear relationship between blood pressure and mortality. This study found that the mortality rate of blood pressure higher than 160/100mmHg and lower than 120/80mmHg was higher than that controlled between 120~139/80~89mmHg.
For this reason, Weiss et al. from the University of Health and Science of Oregon, USA, conducted a retrospective study to explore whether there is a nonlinear relationship between blood pressure and mortality in patients with CKD. The article was published on the recent CJASN.
We included 21015 patients who were over 65 years old and had not been dialyzed in CKD3~5 within two years and registered with Northwest Health Administration from 2000 to 2010.
It was found that the relationship between systolic blood pressure and mortality varied with age. Among all age groups in the study, the mortality rate of systolic blood pressure between 131 and 140 mmHg was the lowest. The relationship between systolic blood pressure and mortality was U-shaped in the 65-70 age group. In the age group above 70, the mortality rate of systolic blood pressure<130mmHg is the highest, while the mortality rate of systolic blood pressure>130mmHg has no difference.
After adjusting for changes in diastolic blood pressure, the same conclusion can still be reached. Similar conclusions were reached by different genders. Except for the 65-70 age group>150 mmHg, this group had the highest mortality rate for men, but not for women.
This makes us rethink whether we should strictly control the blood pressure of elderly patients with CKD.
Controlling systolic blood pressure between 140 and 160 mmHg is particularly important for elderly people with CKD, because many people have basic hypertension. In this trial, 32.7% of patients had a basal systolic blood pressure higher than 140mmHg at the time of enrollment. The elderly have some complications more or less, which will lead to tissue hypoperfusion after lowering blood pressure. So it may be better to relax blood pressure control properly.
For all age groups in this study, there is a linear relationship between diastolic blood pressure and mortality. The lower the diastolic blood pressure, the higher the mortality. Different eGFR did not affect the relationship between systolic blood pressure and mortality. Therefore, CKD patients should consider age when controlling their blood pressure. Young people can control their blood pressure more strictly, but they should carefully consider whether the elderly still follow the guidelines.