Late-Life Hypertension Linked to Lower Dementia Risk

Deborah Brauser

February 03, 2017

Late-life development of hypertension may be protective against dementia — at least if onset occurs after age 80 years — suggest new findings from the ongoing 90+ Study.

In a cohort of more than 500 participants with a mean age of 93 years, those who developed hypertension between the ages of 80 and 90 years had a 42% lower risk for dementia than those without hypertension, and those who developed it after age 90 had a 63% lower risk.

The latter association remained significant even after adjustment for use of any antihypertensive treatment.

The authors, led by María M. Corrada, ScD, professor of neurology and of epidemiology at the University of California Irvine, note that this is the first study to assess links between hypertension and dementia "in the oldest old" and highlights that some dementia risk factors may change over the life course.

"We found that age matters," Dr Corrada told Medscape Medical News. "What we learn about the younger elderly doesn't necessarily apply to older individuals and vice versa."

The findings were published online January 16 in Alzheimer's & Dementia.

Fastest-Growing Population Segment

"We've been interested in learning about what dementia looks like in the oldest old — who are the fastest-growing segment of the population in the US and in many other countries around the world," said Dr Corrada.

"Hypertension in midlife has been shown in other studies to be not good at all, and to increase the risk of dementia in later life," she noted. "So we wanted to investigate what happens to people who develop hypertension in later life. Would it be the same thing?"

The population-based 90+ Study consists of surviving members of the Leisure World Cohort Study, which was created to assess health in almost 14,000 members of a California retirement community.

The current analysis of the 90+ Study included 559 participants (71% women, 99% white) who did not have dementia at baseline and who participated in follow-up visits.

History of hypertension and age at onset were self-reported in questionnaires, and blood pressure measurements were conducted at baseline.

Cognitive assessments included the Mini-Mental State Examination (MMSE) and modified MMSE, the Clinical Dementia Rating Scale, the Functional Activities Questionnaire, the Dementia Questionnaire, and the telephone Cognitive Abilities Screening Instrument.

During a mean follow-up of 2.8 years, 224 of the participants developed dementia and 61% reported a hypertension diagnosis.

Of the cohort, 28% reported hypertension onset before turning 70 years of age, and 19% reported onset after age 80.

Although the risk for dementia development was significantly lower for the participants with hypertension onset between the ages of 80 and 89 years or after age 90 vs those with no history of hypertension, there were no significant associations for those with onset before age 80.

Table. Risk for Dementia by Age of Hypertension Onset

Age at Hypertension Onset (y) Adjusted Hazard Ratioa (95% Confidence Interval) P Value
<70 0.79 (0.56 - 1.11) .17
70 - 79 1.09 (0.69 - 1.73) .72
80 - 89 0.58 (0.34 - 0.98) .04
≥90 0.37 (0.19 - 0.73) .004

aAdjusted for age, sex, education, and heart disease vs those without hypertension.

 

After adjustment for use of antihypertensive medications, the hazard ratio for dementia for the oldest group was still a significantly lower at 0.38 (95% confidence interval, 0.19 - 0.76; P = .007).

Although not statistically significant, dementia risk also declined as the severity of hypertension increased.

"Whether hypertension in the oldest-old is a marker of better health or a necessary compensatory mechanism is not known," write the investigators.

"Individuals who develop hypertension very late in life may be successfully marshalling a physiological compensatory mechanism to maintain adequate cerebral perfusion in the face of age-associated vascular changes," they write.

But the researchers note that more mechanistic research is definitely needed.

Dr Corrada added that because of this, and the fact that theirs was an observational study, they are not suggesting that blood pressure recommendations should be changed in the clinical setting. Instead, it's important to better understand the big picture of brain health.

She added that some of the investigators are now assessing blood flow through imaging "to see how it relates to blood pressure in our participants."

Next Step?

"This was an interesting study from a really solid group of investigators," Heather M. Snyder, PhD, senior director of medical and scientific operations at the Alzheimer's Association, told Medscape Medical News when asked for comment.

"As we look at various risk factors and what they mean throughout the life course, whether it's early life or midlife or late life, really understanding the role they play in brain health is incredibly important," said Dr Snyder.

She noted that the hypotheses as to why the association was found between hypertension and lower dementia risk make sense, although "we don't exactly know" if they're correct.

That said, Dr Snyder pointed out that past research has found an association between higher body mass index in later life and a lower risk for dementia.

"Trying to understand what that means and what's changing in our underlying biology is really where new studies need to go. And it's really the next step now that we're seeing these types of associations," she said.

The study was supported by grants from the National Institutes of Health, the Earl Carroll Trust Fund, and Wyeth-Ayerst Laboratories. The study authors have disclosed no relevant financial relationships.

Alzheimers Dement. Published online January 16, 2017. Abstract

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