“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 said. To examine the relationship between blood pressure and dementia more closely, researchers analysed five double-blind placebo-controlled randomized trials that used different blood pressure lowering treatments and followed patients until the development of dementia. A total of 28,008 individuals with an average age of 69 and a history of high blood pressure from 20 countries were included. Across these studies, the mid-range of follow up was just over four years.
“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,” said Dr Peters. “Our results imply a broadly linear relationship between blood pressure reduction and lower risk of dementia, regardless of which type of treatment was used.” Researchers hope the results will help in designing public health measures to slow the advance of dementia as well as informing treatment, where there may be hesitations around how far to lower blood pressure in older age.
“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 Dr Peters. “But what we still don’t know is whether additional blood pressure lowering in people who already have it well-controlled or starting treatment earlier in life would reduce the long-term risk of dementia,” she added.
Professor Craig Anderson, Director of the Global Brain Health program at The George Institute said, “this work is an important 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.”