Towards the end of 2013 the Eight Joint National Committee (JNC) released the latest guidelines for treatment of adult hypertension. The 14-page document along with 300 pages of online supplement could be summarized into 2 simple messages; keep blood pressure below 150/90 in people over 60 years but below 140/90 in all other adults and that treatment could begin with any one of mainstream anti-hypertensive medication. One could initiate treatment with a thiazide type diuretic, ACE inhibitor, angiotensin receptor blocker (ARB) or a calcium blocker.
The threshold for both diabetics and patients with impaired kidney function was set at 140/90 with the caveat that patients with chronic kidney disease (CKD) initial or add o therapy should be an ACE inhibitor or an ARB. The JNC 8 report came after a decade of JNC 7 published in 2003. The relaxing of treatment threshold in those above 60 years to 150 however stirred up a loud debate with 5 committee members actually writing to the Annals of Internal Medicine that they disapproved the loosening of the threshold. The authors clarified that their article was not intended as an attack on the JNC 8 guidelines but a clarification on the need to persist with 140 as the upper systolic blood pressure limit in elderly. The dissidents noted that raising the target would reverse decades of declining cardiovascular disease (CVD) rates, particularly stroke deaths. Increasing the systolic blood pressure target to 160 would expose the population group most susceptible to cardiovascular disease or already suffering from CVD. One of the authors noted that CVD mortality rate was 35 times higher in those above 60 than those below 60 years. The 2 trials taken into consideration by JNC 8 to justify relaxing systolic threshold (JATOS and VALISH) were not adequately powered.
The problem with blood pressure treatment so far has been that despite 50 years of randomized trials we still remain unclear of how low or how far we should treat it. Numerous rigorous trials have established that treating blood pressure prevent heart attacks, heart failure, strokes and deaths. There was a school of thought that firmly believed that blood pressure rises with age to ensure adequate blood supply to the brain while others were convinced that high blood pressure led to dementia and mini-strokes.
But now after so many years of confusion and debate a major study has been stopped prematurely by a year because it has conclusively demonstrated reduction in mortality, heart attack and stroke in a group of patients treated to systolic blood pressure below 120 as compared 140. The study has revealed that patients assigned to intensive treatment below 120 –far lower than current guidelines of 140 and 150- had risk of death reduced by almost 25% and risk of heart attack, heart failure and stroke by a third.
The Systolic Blood Pressure Intervention Trial (SPRINT) randomized 9361 high-risk hypertensive adults with systolic blood pressures of 130 or more. All participants were more than 50 years of age and had one other risk factor; known CVD, age more than 75 years, chronic kidney disease or having risk of CVD 15% or more over 10 years. The primary outcome was combined cardiovascular outcome of myocardial infarction, heart failure, stroke, acute coronary syndrome or death. Other outcomes such as affect of treatment on chronic kidney disease, dementia or MRI changes continue to be looked into.
Treatment in SPRINT was done with the 4 major anti-hypertensive medicines recommended but with emphasis on thiazide diuretics because of the ALLHAT study. Other drugs such as beta-blockers or spironolactone inhibitors could be used when required. SPRINT importantly was entirely funded by the National Institute of Health and not by the industry. SPRINT did not include diabetics because the ACCORD trial had not shown any advantage of lowering blood pressure below 120 as compared to below 140 in patients with diabetes. The primary outcome of mortality was not reduced in ACCORD albeit stroke was significantly less in the intensely treated group but this was a secondary outcome. Blood pressures achieved in SPRINT were almost as that achieved in ACCORD, an average of 134 in the standard group versus 119 in the intensively treated group.
The SPRINT trial includes a sub-study SPRINT-MIND that investigates effects whether the lower target blood pressure cuts down dementia, delays decline in cognition and effects on kidney function are also being explored. The results of lower blood pressure on the brain and kidney continue to be investigated. Getting to a pressure below 120 may have a flip side as elderly people already on other drugs for co-morbidities could be vulnerable to drug interaction or dizziness and falls. More than a quarter of patients in SPRINT were more than 75 years.
So how does the physician apply the results of the SPRINT trial in daily practice? Frankly because details of the study have still not been provided applying them will be difficult for now. Despite announcement of relative reduction of mortality and CV events the absolute reductions in clinical events have not been revealed as yet; we therefore cannot calculate the number of patients required to achieve clinical benefit by aggressive lowering of blood pressure. The information on which drug was most effective or whether all drugs were equally effective has also not been officially declared. We also are unaware about the various side effects borne by patients or which age group benefited the most by intensive treatment. We therefore will have to wait for the full paper to be published before striving to lower blood pressure under 120 with additional drugs. The study will be presented after some months and probably published early in 2016.
High blood pressure is the most common chronic medical ailment and more than a third of Indians from their thirties suffer from it. Surprisingly the rates in India are similar in rural and urban people. It is estimated that more than a billion have hypertension worldwide. It is hence important to analyze the raw data from SPRINT before administering additional drugs to achieve sub 120 blood pressure with the dangers of exposure to new side effects and added costs.