Monday, October 28, 2013

Is High Blood Pressure In The Elderly Not As Risky?

The risks associated with hypertension, high blood pressure (BP) as it's commonly called, may be different for very old compared to younger adults. Paula Span, who writes the New Old Age Blog at the New York Times discussed this in her post:

For the Very Old, a Surprise in Blood Pressure Readings, New York Times, 8 August 2012

Span writes:
"I was startled to learn that in the very elderly - those over 85, say - high blood pressure may indicate better health while lower numbers could mean trouble ahead."
Span had been reading a study and an accompanying editorial published in the Archives of Internal Medicine last year:

Rethinking the Association of High Blood Pressure With Mortality in Elderly Adults, JAMA Internal Medicine, August 2012
Comment on “Rethinking the Association of High Blood Pressure With Mortality in Elderly Adults," Goodwin JS, JAMA Internal Medicine, August 2012

In his editorial, Goodwin offered some background:
"In 1988, Matilla et al reported that, among the very old, elevated systolic and diastolic blood pressure (BP) were associated with longer survival. The differences were not subtle. The 5-year survival of those with systolic BPs greater than 200 mm Hg were almost twice as high as those with levels of 120 to 140 mm Hg. Over the ensuing 25 years, a substantial number of population-based studies have reported the same findings: in those older than 85 years (or older than 80 years in some studies), high BP is an excellent prognostic sign.

Perhaps the most rigorous assessment came from the Framingham Study, which reported that the strong positive association of BP with cardiovascular mortality was reversed between the ages of 75 and 85. Importantly, no population-based study has found the opposite, that high BP is a marker for bad outcomes in octogenarians. Conversely, “normal” BP is bad. Perhaps the worst sign is falling BP."
Why does high BP appear to be a good sign in an older population? Goodwin explains that the old are a mixture of frail and more robust individuals.  High BP does not connote the same level of health in both groups.  Referring to Diehr et al. he said:
"[The very old] showed a steady decrease in BP in the 3 years before death. ... High BP is only a good sign in very old age because many of those with “normal” BP have it for bad reasons."
When is it advantageous to treat high blood pressure in an older person? Goodwin says:
"Many robust, very old individuals have hypertension. Antihypertensive treatment in those individuals is beneficial. Frail older individuals are less likely to have hypertension, and treating those who do may produce bad outcomes."
How do you measure robustness? One good test is walking speed.

In the study at the top of this post, those with hypertension who could walk a 20-foot corridor at an average pace of 1.8 mph or better had about the same risk of dying as younger adults. Those with high BP who walked slower did not have an increased risk. And those with high BP who couldn't complete the walk had a 60% lower risk of death:
"Higher systolic BP was associated with an increased risk of mortality only among elderly adults who had a medium to fast walking pace. In contrast, among slower-walking older adults, there was not an association between elevated systolic or diastolic BP and mortality. Strikingly, we found elevated systolic and diastolic BP was strongly and independently associated with a lower mortality risk in participants who did not complete the walk test."
The lead author of the study, Dr. Michelle Odden, said:
"The paradigm in medicine is, high blood pressure is bad, treating it is good. We’re saying, maybe we need to look more closely at the guidelines and tailor them more to older adults."