by Rebecca Hiscott
Middle-aged adults with elevated blood pressure may experience greater cognitive deficits in later years, according to a 20-year cohort study published in the August 4 online issue of JAMA Neurology. Past studies have reliably demonstrated a link between high blood pressure and increased risk of stroke and dementia, but the latest research suggests that even moderately elevated blood pressure can have an impact on cognition later in life.
The study, which collected blood pressure and cognitive data from 13,476 adults between 1990-1992 and 2011-2013, found that adults who had hypertension or prehypertension between the ages of 48 and 67 experienced greater declines in cognition two decades later.
“Basically the amount of decline we see associated with hypertension is pretty modest, but this amount is equivalent to being 2.7 years older at the start compared to not having it,” study author Rebecca F. Gottesman, MD, PhD, associate professor of neurology and epidemiology at the Johns Hopkins University School of Medicine, said in a recent interview. “Even having prehypertension, which often isn’t treated, was associated with some cognitive decline,” she added.
The study examined a subset of participants from the Atherosclerosis Risk in Communities (ARIC) Study, initiated in the late 1980s. Participants were tested for systolic and diastolic blood pressure and overall cognition at baseline. Adults with systolic blood pressure (SBP) of less than 120 millimeters of mercury (mm Hg) and diastolic blood pressure (DBP) of less than 80 mm Hg were characterized as having normal blood pressure; those with SBP of 120-139 mm Hg and DBP of 80-89 mm Hg were characterized as having prehypertension; and any participant with SBP higher than 140 mm Hg and DBP higher than 90 mm Hg was characterized as having hypertension.
Adults who had hypertension at baseline were twice as likely to have died by 2011 as adults with normal or slightly elevated blood pressure, the authors noted.
Over a median follow-up time of 19.1 years, the researchers evaluated participants’ global cognition and administered tests measuring verbal- and short-term memory, executive function and processing speed, as well as expressive language. Participants were given a baseline cognitive assessment between 1990 and 1992, and took the tests again in 1996-1998, and in 2011-2013.
Although all study participants saw some cognitive decline over two decades, those who had hypertension at baseline were associated with a 6.5 percent greater decline in cognitive function by the end of the study than those who had normal blood pressure at baseline. Adults with prehypertension at baseline were associated with a 4.8 percent greater decline in cognition. Interestingly, participants who had hypertension at baseline but were treating the condition with antihypertensive drugs had slightly better outcomes than adults with untreated hypertension, with cognition scores comparable to those of adults with prehypertension.
In contrast, developing high blood pressure later in life seemed to have no effect on global cognition, the authors observed. “The lack of an association between current (late-life) BP and prior cognitive change in our study…supports the view that, at the population, higher BP in later life may be less detrimental, perhaps because hypertension at a later age reflects new conversion or because of reverse causation,” they wrote.
The authors noted that although the extra cognitive decline associated with hypertension is modest, “it is enough to increase the public health burden of hypertension and prehypertension significantly.” In a news release, Dr. Gottesman added that, “we need to pay attention to hypertension at a relatively young age, long before the health problems of old age set in. People should really know what their blood pressure is and what their doctor plans to do if it’s elevated.”
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