How lowering blood pressure could prevent dementia, and why you shouldn’t wait until midlife to adopt a control regime
In new research revealed last week, people whose blood pressure was strictly controlled over several years were 15 per cent less likely to be diagnosed with mild cognitive impairment and subsequent dementia
For those with high blood pressure who hope to ward off dementia, doctors have the same advice for those looking to protect their hearts and kidneys: go lower.
In a comprehensive new study, researchers found that driving down systolic blood pressure to a new lower target level reduced their risk of developing mild cognitive impairment, or MCI, by close to 20 per cent.
MCI is a decline in memory and thinking skills that is slight, but noticeable, and it affects between 15 and 20 per cent of people over 65. For as many as half of those diagnosed with MCI, a diagnosis of dementia will come later.
The new research found that subjects whose blood pressure was more strictly controlled were 15 per cent less likely to be diagnosed with mild cognitive impairment and subsequent dementia.
The new findings, presented last week at the Alzheimer’s Association’s International Conference in Chicago, come a year after the American Heart Association and the American College of Cardiology adopted a new target for those with hypertension. Physicians groups had long considered blood pressure readings of 140/90 mmHG to be an acceptable target for those with hypertension, but in 2017, they urged physicians to get their patients with high blood pressure to 130/80 mmHG.
The new research suggests that there are powerful benefits to getting the first number in that reading – systolic blood pressure – to an even lower target: 120 mmHG.
Systolic blood pressure is the amount of pressure in a person’s arteries during the contraction of the heart muscle. Because it is the highest pressure to which the blood vessels are subjected, systolic blood pressure is thought to have the most detrimental impact on the delicate capillaries that nourish the brain, as well as the kidneys, heart and liver. In large populations, lowering that reading to 120 has already been found to reduce rates of cardiovascular disease and kidney failure.
The new findings emerge from a clinical trial called Sprint (short for Systolic Blood Pressure Intervention Trial), which began in 2010 and ran for less than five years. After trial subjects had been followed for an average of just over three years, the trial was shut down because the findings showed so strongly the benefits of the lower systolic blood pressure goal in protecting people’s hearts. In August 2015, a board of safety monitors said it could no longer justify maintaining some of the trial’s subjects at the systolic target level of 140 mmHG.
“What Sprint has shown is that what is good for your heart is also good for your brain,” said Dr Jeff Williamson of the Wake Forest School of Medicine, lead author of the Sprint Mind part of the study (Mind is short for Memory and Cognition in Decreased Hypertension), who presented the findings last week in Chicago.
Williamson called it “very encouraging” that even a brief period of more intensive blood pressure control would show such powerful protective effects for the brain as well. Had the trial run longer, he said, there is reason to believe that even more cases of mild cognitive impairment and dementia might be prevented.
The Sprint Mind trial’s 8,626 subjects ranged in age from 50 to 100. None had diabetes, but all were considered to be at increased risk of cardiovascular disease. After a year in the trial, those assigned to have their blood pressure treated to the stricter target had achieved an average systolic blood pressure reading of 121.4 mmHG. Those assigned to the “standard treatment group” had an average systolic blood pressure reading of 136.2 mmHG.
Dr Lon Schneider, an Alzheimer’s specialist at the University of Southern California’s Keck School of Medicine, hailed the findings. But he suggested that the average age of the trial’s subjects – 68 – may obscure an important point: that strict blood pressure control is likely to prevent dementia most effectively if it starts early and is followed through midlife.
That is because hypertension causes harm to blood vessels cumulatively over many years, Schneider said. Research suggests that decades before declines in memory and thinking skills are noticeable, high blood pressure may begin to damage the brain’s complex network of tiny blood vessels and set the stage for further damage.
Blood pressure control is important at all ages, Schneider added. But in midlife, stricter control may prevent the onset of blood vessel damage. If it does not begin until a person is already at a later age, it may be too late to stop that slide toward end-organ damage and, in the case of the brain, dementia.