Effect of blood pressure on the aging brain depends on genetics

July, 2012

For those with the Alzheimer’s gene, higher blood pressure, even though within the normal range, is linked to greater brain shrinkage and reduced cognitive ability.

I’ve reported before on the evidence suggesting that carriers of the ‘Alzheimer’s gene’, APOE4, tend to have smaller brain volumes and perform worse on cognitive tests, despite being cognitively ‘normal’. However, the research hasn’t been consistent, and now a new study suggests the reason.

The e4 variant of the apolipoprotein (APOE) gene not only increases the risk of dementia, but also of cardiovascular disease. These effects are not unrelated. Apoliproprotein is involved in the transportation of cholesterol. In older adults, it has been shown that other vascular risk factors (such as elevated cholesterol, hypertension or diabetes) worsen the cognitive effects of having this gene variant.

This new study extends the finding, by looking at 72 healthy adults from a wide age range (19-77).

Participants were tested on various cognitive abilities known to be sensitive to aging and the effects of the e4 allele. Those abilities include speed of information processing, working memory and episodic memory. Blood pressure, brain scans, and of course genetic tests, were also performed.

There are a number of interesting findings:

  • The relationship between age and hippocampal volume was stronger for those carrying the e4 allele (shrinkage of this brain region occurs with age, and is significantly greater in those with MCI or dementia).
  • Higher systolic blood pressure was significantly associated with greater atrophy (i.e., smaller volumes), slower processing speed, and reduced working memory capacity — but only for those with the e4 variant.
  • Among those with the better and more common e3 variant, working memory was associated with lateral prefrontal cortex volume and with processing speed. Greater age was associated with higher systolic blood pressure, smaller volumes of the prefrontal cortex and prefrontal white matter, and slower processing. However, blood pressure was not itself associated with either brain atrophy or slower cognition.
  • For those with the Alzheimer’s variant (e4), older adults with higher blood pressure had smaller volumes of prefrontal white matter, and this in turn was associated with slower speed, which in turn linked to reduced working memory.

In other words, for those with the Alzheimer’s gene, age differences in working memory (which underpin so much of age-related cognitive impairment) were produced by higher blood pressure, reduced prefrontal white matter, and slower processing. For those without the gene, age differences in working memory were produced by reduced prefrontal cortex and prefrontal white matter.

Most importantly, these increases in blood pressure that we are talking about are well within the normal range (although at the higher end).

The researchers make an interesting point: that these findings are in line with “growing evidence that ‘normal’ should be viewed in the context of individual’s genetic predisposition”.

What it comes down to is this: those with the Alzheimer’s gene variant (and no doubt other genetic variants) have a greater vulnerability to some of the risk factors that commonly increase as we age. Those with a family history of dementia or serious cognitive impairment should therefore pay particular attention to controlling vascular risk factors, such as hypertension and diabetes.

This doesn’t mean that those without such a family history can safely ignore such conditions! When they get to the point of being clinically diagnosed as problems, then they are assuredly problems for your brain regardless of your genetics. What this study tells us is that these vascular issues appear to be problematic for Alzheimer’s gene carriers before they get to that point of clinical diagnosis.

Recent posts at Mynd

A study involving 97 healthy older adults (65-89) has found that those with the “Alzheimer’s gene” (APOe4) who didn’t...

An Indian study involving 648 dementia patients, of whom 391 were bilingual, has found that, overall, bilingual patients developed dementia 4.5...

A study, involving 371 patients with mild cognitive impairment...

A study involving 206 spousal and adult children caregivers of dementia sufferers (mostly Alzheimer’s) has found that about 84% of...

A study involving 254 people with dementia living at home has found that 99% of people with dementia and 97% of their caregivers had one or more...

A new U.S. study suggests that Alzheimer's disease and other dementias are markedly under-reported on death certificates and medical records....

It’s often argued that telling people that they carry genes increasing their risk of Alzheimer’s will simply upset them to no purpose...

11 new genetic susceptibility factors for Alzheimer’s identified

The largest international study ever conducted on Alzheimer's...

Understanding a protein's role in familial Alzheimer's...

A brain imaging study of 162 healthy babies (2-25 months) has found that those who carried the ApoE4...

A gene linked to Alzheimer's has been linked to brain changes in childhood. This gene, SORL1, has two connections to Alzheimer’s: it...

Analysis of data from 237 patients with mild cognitive impairment...

Two studies indicate that young people carrying the “Alzheimer’s gene” (ApoE4...

Analysis of data from more than 8,000 people, most of them older than 60, has revealed that, among the 5,000 people initially tested cognitively...

Analysis of 700 subjects from the Alzheimer's Disease Neuroimaging Initiative has revealed a genetic mutation (rs4728029) that’s associated...

Analysis of brain scans and cognitive scores of 64 older adults from the NIA's Baltimore Longitudinal Study of Aging (average age 76) has found...