The SPRINT trial

SPRINT is the randomised trial that pushed blood-pressure targets down: in high-risk adults over 50, aiming for a systolic pressure below 120 rather than below 140 cut major cardiovascular events by about a quarter and deaths by 27%. The benefit was real but came with more fainting and kidney injury, it faded once the treatment eased off, and its much-quoted brain result is a reduction in mild cognitive impairment, not in dementia.

Read SPRINT as strong evidence that lower blood pressure saves lives in people at high risk, as long as the treatment continues. It is not proof that tight control prevents dementia, and its harms are a reason to report any faintness or light-headedness on a tight target.

What the trial tested

The Systolic Blood Pressure Intervention Trial (SPRINT) randomised 9,361 adults aged 50 and over at high cardiovascular risk to one of two systolic goals: below 120 mm Hg (intensive control) or below 140 mm Hg (standard control). Systolic pressure is the top number of a reading. Entry required a systolic pressure of 130 or higher plus at least one other cardiovascular risk factor. People with diabetes, a previous stroke or polycystic kidney disease were excluded. The trial was stopped early, after a median of about three and a quarter years (3.26).^[1]

The main result: fewer events and deaths

The intensive target cut major cardiovascular events by about 25%, from 2.19% of the standard group per year to 1.65% of the intensive group, and deaths from any cause by 27%. In absolute terms, one heart attack, stroke or similar event was prevented for every 61 people treated, and one death for every 90.^[2]

The over-75s did at least as well. Among participants aged 75 and over, the intensive target cut cardiovascular events by about a third and deaths by about a third: 27 people needed treating for three years to prevent one cardiovascular event and 41 to prevent one death, roughly half the numbers for the trial as a whole. The benefit held even in the frailest participants and those with the slowest walking speed.^[3] The European guideline notes that these participants probably had no more than mild frailty, so evidence for the very frail is thinner.^[4]

The harms

Per 100 people treated over the trial, the intensive group had roughly 1.8 more episodes of acute kidney injury, 1.4 more of seriously low blood pressure and 1.1 more faints. A measured drop in pressure on standing (orthostatic hypotension) was, unexpectedly, slightly less common in the intensive group.^[5] Injurious falls did not differ between the groups, even in people aged 85 and older.^[6]

The benefit lasted only as long as the treatment

After the trial ended and participants went back to usual care, their pressures drifted back up. Among the 2,944 whose routine clinic records were tracked, average systolic pressure in the intensive group rose from about 133 at five years to about 140 at ten. By a median of 8.8 years of total follow-up there was no longer any evidence of a benefit for cardiovascular or all-cause mortality.^[7] Blood-pressure control works as a lifelong habit, not as a course.

SPRINT-MIND: the brain result, read carefully

SPRINT-MIND followed the same participants for memory and thinking. Its main question, fewer cases of probable dementia, came back not significant; the investigators attribute that partly to the trial stopping early with fewer dementia cases than it was designed to detect. What did show up, on secondary outcomes, was a 19% lower rate of mild cognitive impairment and a 15% lower rate of mild cognitive impairment or probable dementia combined.^[8]

Brain scans, a few hundred of them out of the 9,361 randomised, showed a smaller increase in white-matter lesions, the imaging marker of damage to the brain's small vessels, though both groups still worsened. The same scans found slightly more total brain shrinkage with intensive treatment, a small difference whose meaning is unclear.^[9] Blood flow to the brain rose rather than fell, the opposite of the harm clinicians had long feared from pushing systolic pressure below 120.^[10]

At a median of seven years, the effect was still there but shrinking: mild cognitive impairment about 13% lower, the combined outcome about 11% lower, and probable dementia alone still not significantly reduced. Only 4,232 participants, 59% of those eligible, were assessed, and no scans were repeated, so "lasting" is the strongest word the data will carry.^[11] The first randomised trial to lower dementia itself was a later village-level programme in rural China, covered in Blood pressure.

What later trials added

SPRINT's exclusion of people with diabetes or a previous stroke was for a decade the main objection to applying it widely. Two later trials, both run in China, included many of those people. One, in 11,255 high-risk adults including thousands with diabetes or a past stroke, found major events in 9.7% on the tight target against 11.1% on the standard one, with the same benefit regardless of diabetes or stroke history.^[12] The other, in 12,821 adults with type 2 diabetes, also found fewer events on the lower target.^[13] Both benefits were smaller than SPRINT's, about an eighth and a fifth fewer events rather than a quarter, which is the more realistic expectation. The harms looked familiar: more fainting in the first, and more symptomatic low blood pressure and high potassium in the second, with overall serious side effects similar between the groups.

What to do

If you are at high cardiovascular risk, treat SPRINT as the reason a lower target is worth pursuing, and ask what target suits you; the guideline targets are in Blood pressure.
Report faintness or light-headedness on a tight target: that is where the trial's harms showed up.
Don't stop treatment once the numbers look good. The benefit disappeared when pressures drifted back.
Count the brain benefit as less mild cognitive impairment, not proven dementia prevention. The wider picture is in Dementia prevention.