Blood pressure variability associated with increased risk of dementia, especially in men

Aug 30, 2021

High long term blood pressure variability (BPV) in older adults, particularly men, is associated with an increased risk of dementia and cognitive decline.

 

A new analysis of ASPREE data found a link between variability of blood pressure in older adults, particularly in men, and an increased risk of dementia and cognitive decline.

Hypertension (high blood pressure) in mid-life has previously been shown to be a strong risk factor for dementia in later life. This study showed that fluctuations in blood pressure (BPV), are also an indicator of possible decline in cognition (thinking and memory).

ASPREE investigators, Professor Mike Ernst from the University of Iowa and Associate Professor Joanne Ryan from the School of Public Health and Preventive Medicine, Monash University led the study, which analysed health data from 16,758 ASPREE participants, mostly aged over 70 years.

White man with greying beard, wearing a grey jumper sits in front of bookshelf lined with books.

Above: US-based ASPREE investigator, Prof Mike Ernst led this study with A/Prof Joanne Ryan.

Previous studies into BPV involved younger people or older adults already diagnosed with cognitive impairment, or used a single cognitive measuring tool.

Prof Ernst said ASPREE was uniquely suited to investigate the effect of BPV on cognition because participants were free of dementia at the start of the trial and they underwent standardised blood pressure and cognition measures for several years.

“Importantly, participants underwent a series of cognitive measures. This enabled us to capture detail on many facets of cognition and memory, including global cognition, delayed episodic memory, verbal fluency, and processing speed and attention.

“They also underwent a validated depression scale prior to annual cognitive exercises, which is important because depression may have an impact on cognitive function,” said Prof Ernst.

Blood pressure was recorded for all participants annually, and was done so in accordance with guidelines from the American Heart Association.

Researchers categorised participants into three BPV groups: low, medium and high, based on blood pressure measures recorded in the first three years of the study. At study entry, BPV was generally higher among women, but cognitive scores were similar in all groups.

Over an average of 4.7 years, differences emerged. Participants with the highest BPV were shown to be at significantly increased risk of dementia and cognitive decline compared with the group with the smallest fluctuations in blood pressure. Being male also increased the risk significantly, regardless of antihypertensive use and other dementia risk factors such as smoking.

Researchers found no association between systolic or diastolic blood pressure measures, or hypertension at study entry, and the risk of dementia/cognitive decline.

Woman with brown hair, fair skin wearing a red and white jacket stands with her arms crossed and smiling at the camera

Above: Australia-based ASPREE Investigator, A/Professor Joanne Ryan. 

These findings support the earlier studies that had suggested BPV may be a useful indicator of cognitive decline, expanding our understanding to include older, relatively healthy adults who had reached late life without significant cognitive impairment – a group that is not typically considered at high risk for dementia in their remaining lifespan.

The results also provide the first evidence of possible sex‐specific effects of BPV on cognition.

The biological mechanisms underpinning the relationship between BPV and cognitive decline remain unclear, which the researchers say should be a focus of further investigation.

Accumulating evidence suggests BPV is associated with structural brain changes, including increased lesions in the brain called white matter hyperintensities, increased small bleeds in the cerebrum, and enlarged fluid-filled spaces in the brain matter. Whether these changes are caused by BPV or vice versa is unknown.

While all ASPREE participants were without symptoms of cognitive impairment at study entry, it is possible that some may have had changes to brain structure without showing symptoms.

Professor Ernst said that it was tempting to speculate about the existence of different pathways towards cognitive decline in men and women, such as whether sex hormones such as oestrogen may have a protective effect for women.

“More study is warranted into this area to help determine the underlying reasons for these sex-specific differences, and into research to find out whether reducing BPV can preserve late-life cognitive function,” he said.

Published in the Journal of the American Heart Association, the findings may help doctors identify people at increased risk of cognitive impairment, allowing for closer monitoring, and pointing the way to new areas for research.

A/Prof Ryan said that dementia prevention remains a major public health priority.

“Any opportunity to identify early those at risk, and engage people in preventive therapies, is important.”

The paper, ‘Long-Term Blood Pressure Variability and Risk of Cognitive Decline and Dementia Among Older Adults’,  was published in the Journal of the American Heart Association.
DOI: 10.1161/JAHA.120.019613

This new paper is one of many important health findings yielded from the ASPREE (ASPirin in Reducing Events in the Elderly) dataset.  Further analysis of the extensive, high quality data from 19,114 Australian and Americans, continues to drive new findings in healthy older adults, mostly over the age of 70.

This post was adapted from this article.

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