New Hypertension After 80 Linked to Lower Dementia Risk

Susan Jeffrey

July 14, 2014

COPENHAGEN, Denmark — New results from the 90+ Study show that new hypertension after 80 years of age is not only not a risk factor for dementia but is actually associated with reduced risk.

In a longitudinal study of participants aged 90 years and older without dementia at study entry, researchers report that those who developed hypertension between the ages of 80 and 89 years had a significantly lower risk of developing dementia than their peers without hypertension. Further, those with hypertension onset after 90 years of age had an even lower risk, a 55% reduction vs those without hypertension.

"It seems like for people at very old ages, developing hypertension may be beneficial for maintaining intact cognition," lead author Maria Corrada, MS, ScD, from the University of California, Irvine, concluded.

One hypothesis is that a certain level of blood pressure may be required to maintain adequate blood flow and oxygenation in the more elderly brain, Dr. Corrada speculated.

"But we need to actually do more research to understand better what this risk-benefit ratio of treating this new-onset hypertension at this age is in relation to dementia and other outcomes," she added, as well as to determine what the standard of care should be in those over 90 years of age, currently the fastest-growing segment of the population.

The results were presented here at the Alzheimer's Association International Conference (AAIC) 2014.

90+ Study

Dr. Maria Corrada

Many studies have shown that hypertension in midlife is associated with a higher risk for dementia in the elderly, Dr. Corrada explained. "But there's also evidence to suggest that that association changes with age," she said, such that among those at more advanced age, hypertension may lower the risk for dementia.

To look at this relationship more closely, the researchers investigated whether the risk for all-cause dementia in a cohort of the "oldest old" varies with the age at which hypertension was first diagnosed.

The 90+ Study is an ongoing population-based longitudinal study of people aged 90 and older who are surviving participants of the previous Leisure World Cohort Study initiated in 1981. In the Leisure World study, participants answered a mailed questionnaire about their health and lifestyle factors. Participants who survived and were 90 or older in 2003 or later were invited to take part in the 90+ Study, with principal investigator Claudia Kawas, MD, also at the University of California, Irvine.

As part of these studies, participants were asked whether they were ever diagnosed with hypertension and, if so, at what age. For this analysis, 625 participants without dementia at their 90+ Study baseline visit were followed every 6 months with a multidisciplinary assessment for up to 10 years, with a mean follow-up of 2.8 years. Most were women (69%), with an average age of 93 years at enrollment in the 90+ Study. The cohort was relatively highly educated, Dr. Corrada noted, with 43% having a college education or higher.

Of these, 259 developed dementia over follow-up, 41% of the cohort. For people who developed hypertension before age 80, their risk for dementia was not different from the risk in those without hypertension, Dr. Corrada noted.

"However, people that developed hypertension in their 80s, their risk was actually lower compared with people without hypertension, a 41% lower risk compared to that group," she said. "And for people who developed hypertension even later, in their 90s, the risk was even lower, 55% lower risk compared to people without a history" of hypertension.

Table 1. Risk for Dementia Relative to Hypertension Age at Onset vs No Hypertension

Age at Hypertension Onset (y) Relative Risk
<70 0.88
70-79 1.13
80-89 0.59
90+ 0.45

 

Dr. Corrada pointed out that these estimates are based on participant self-report, but they also had measured blood pressures taken at the time of enrollment in the 90+ Study. Relative to those with normal blood pressure, she said, "what we see is a trend with decreasing risk of dementia with increasing levels of blood pressure, with the lowest risk in the group with the highest levels of blood pressure, which here is stage 2 hypertension (P for trend = .05)."

Table 2. Risk for Dementia by Measured Blood Pressure at 90+ Study Baseline

Blood Pressure Category (mmHg) Relative Risk
<120 systolic or < 80 diastolic Reference
129-139 systolic or 80-89 diastolic 0.76
140-169 systolic or 90-99 diastolic 0.72
160+ systolic or 100+ diastolic 0.58

 

This analysis was adjusted for use of antihypertensive treatment, she noted, "so the association was not due to the medications that they may have been taking."

Further research on this phenomenon is planned, Dr. Corrada told Medscape Medical News. Some of the 90+ Study participants have agreed to donate their brain upon death, and the investigators are interested to find ways to study their cerebral blood flow. "There's a lot that needs to be done before any recommendations can be made," she said.

How Aggressively to Lower BP?

William Klunk, MD, PhD, distinguished professor of psychiatry and neurology at the University of Pittsburgh School of Medicine, Pennsylvania, and a member of the Alzheimer's Association's Medical and Scientific Advisory Council, moderated a press conference here that featured this new research.

Dr. William Klunk

Asked for comment on these findings, Dr. Klunk said, "I guess what I take home from that is it may be that one size does not fit all for hypertension." As people age, it's possible that what's "normal" isn't the optimal target of 120/80 mmHg put forward for those who are younger, he pointed out. "I think what we have to be careful of is, is the message of that study that we shouldn't take people who are at 150/90 and decrease them to 120/80 (mmHg)?"

"That's probably a safer interpretation than if I find somebody who's doing well at 90 at 120/80 and feed them salt and try to get them up to 150/90," Dr. Klunk told Medscape Medical News. "I don't think that's necessarily the implication of this study — that we want to be raising blood pressure — but I think it really questions how aggressively we want to lower blood pressure at that age."

The study was funded by the National Institutes of Health, the Alzheimer's Association, and the Earl Carroll Trust Fund. The authors have disclosed no relevant financial relationships.

Alzheimer's Association International Conference (AAIC) 2014. Abstract P2-083. Presented July 14, 2014.

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