New research suggests hypertension may protect against dementia in older individuals

Written by Martha Powell

A new study, published recently in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, has reported that the onset of hypertension in later life may lead to a reduced risk of dementia in those over 90 years of age. Understanding the mechanisms behind this association could uncover options for protecting against dementia in individuals in their 80s and 90s.

The researchers examined 559 individuals for an average of 2.8 years in order to assess the relationship between blood pressure and dementia. All participants were from The 90+ Study, a long-term, population-based study of those over 90years of age. Dementia was not present in any of the participants at enrollment; however, during the follow-up period a total of 224 individuals developed dementia.

The group observed that the onset of high blood pressure in later life may protect against dementia. Specifically, the team discovered that individuals who reported hypertension between 80 and 89 years of age were 42% less likely to develop dementia aged 90 or older, compared with those who had no history of high blood pressure.

Cardiovascular risk factors, such as hypertension, have previously been thought to increase the risk of dementia; however, these new results suggest that this relationship may not be as clear as first thought and could alter over the course of an individual’s lifetime.

Lead author Maria Corrada (University of California, Irvine; CA, USA) reported:  “In this first-of-its-kind study, we find that hypertension is not a risk factor for dementia in people age 90 or over, but is actually associated with reduced dementia risk.”

The researchers observed that this association was not affected by whether individuals were taking medication to treat their hypertension. In addition, they suggested that participants’ dementia risk appeared to decrease as the severity of hypertension increased, although the results supporting this were not statistically significant.

The team hypothesized that  blood pressure may need to reach a certain level to maintain adequate blood flow in the brain for normal cognition, and that as we age this level may increase.

Maria Carrillo, Chief Science Officer at the Alzheimer’s Association (IL, USA), commented:  “We need to understand the bigger picture of what protects brain health throughout our entire lives, including our later years. Looking at dementia in this group is critical since it is the fastest growing segment of the US population with the highest rate of dementia.”

However, this study does have some limitations: for example, it included a large proportion of women, and therefore the cohort may not be representative of the entire oldest old population. Further research is needed to investigate this association between hypertension and dementia, and to try and understand the mechanism behind it.

Corrada concluded: “Before we can make the leap to suggesting changes to blood pressure recommendations for reducing dementia risk in clinical care, we need more research to confirm and explain our findings. This includes investigations into the underlying biology of hypertension and brain function.”

Sources: Corrada MM, Hayden KM, Paganini-Hill A et al. Age of onset of hypertension and risk of dementia in the oldest-old: The 90+ Study. Alzheimers Dement. doi:10.1016/j.jalz.2016.09.007 (2017) (Epub ahead of print);