Oct. 25 (UPI) -- A global study involving 28,000-plus people offers the strongest evidence to date that lowering high blood pressure in seniors can reduce the risk of dementia, researchers said Tuesday.
Without significant treatment breakthroughs for dementia, reducing the risk of developing the disease would be "a welcome step forward," Ruth Peters, associate professor at the University of New South Wales in Sydney, Australia, said in a news release.
"Our study provides the highest grade of available evidence to show that blood pressure lowering treatment over several years reduces the risk of dementia, and we did not see any evidence of harm," said Peters, who is program lead for dementia at The George Institute's Global Brain Health Initiative in Newtown, New South Wales, Australia.
What remains unknown is whether additional blood pressure lowering "in people who already have it well-controlled," or whether starting treatment earlier in life, would reduce the long-term risk of dementia, Peters said.
According to Peters, many clinical trials have examined the health benefits of lowering blood pressure. But not many trials included dementia outcomes and fewer still were placebo-controlled, a study design considered to provide the best level of evidence.
"Most trials were stopped early because of the significant impact of blood pressure lowering on cardiovascular events, which tend to occur earlier than signs of dementia," she explained.
The new study examined the relationship between blood pressure and dementia by analyzing five double-blind, placebo-controlled, randomized trials that used different treatments to lower blood pressure. Patients were followed until dementia developed.
Overall, the meta-analysis included 28,008 people from 20 countries who averaged 69 years old and had a history of high blood pressure. Across the studies, participants were followed for just over four years, on average.
"We found there was a significant effect of treatment in lowering the odds of dementia associated with a sustained reduction in blood pressure in this older population," regardless of which type of hypertension treatment was used, Peters said.
The researchers said they anticipate the results will help design public health measures to slow the advance of dementia and inform treatment, since "there may be hesitations around how far to lower blood pressure in older age."
Professor Craig Anderson, director of the Global Brain Health program at The George Institute, said the work may serve as a foundation for clinical trials "to provide reliable estimates of the benefits and risks of preventative treatments, and how best to apply them across different populations."
The research manuscript has been accepted for publication in the European Heart Journal.