Unstable blood pressure may have cognitive consequences in the elderly
medwireNews: Increased visit-to-visit blood pressure variability is associated with impaired cognition in elderly patients with risk factors for cardiovascular disease, shows a secondary analysis of a randomized, controlled trial.
The researchers say that the magnitude of effect found in their study is similar to that of the apolipoprotein E4 genotype on cognition. Given that the apolipoprotein E4 genotype is a well-established risk factor for dementia and Alzheimer’s disease, they believe that the effect of blood pressure variability “can be considered clinically relevant.”
The 5461 patients in the study, who were aged 70–82 years, had their blood pressure measured every 3 months and their cognitive performance assessed at the end of follow-up, which averaged 3.2 years. Their average blood pressure was somewhat elevated, at 153.1/82.5 mmHg, but the effect of variability was independent of actual blood pressure, although the two weakly correlated.
Variability in both systolic and diastolic blood pressure (represented by the standard deviation [SD]) was significantly associated with cognitive performance on a range of measures, the team reports in BMJ.
For example, patients in the highest third of visit-to-visit systolic blood pressure variability (SD 16.3–64.4) required 3.08 seconds more to complete the Stroop test than did patients in the lowest third (SD 0.7–12.2). They also coded 1.16 fewer letters in the letter-digit coding test and recalled significantly fewer pictures in the picture–word learning test: 0.27 fewer for immediate recall and 0.30 fewer for delayed recall. The differences were independent of variables including age, gender, apolipoprotein E genotype, education, and blood pressure.
Furthermore, increased systolic blood pressure variability was associated with reduced hippocampal volume and an increased risk for cortical infarcts in a subset of 553 patients who underwent brain imaging. Increased diastolic variability was linked to cortical infarcts and microbleeds.
However, researcher Simon Mooijaart (Leiden University Medical Center, the Netherlands) and co-workers caution that it is “still unclear whether higher variability in blood pressure is a cause or consequence of brain disease.” They note: “It has been suggested that higher variability itself could originate from previously established brain diseases disturbing central autonomic control.”
The team concludes that “future long term investigations are warranted to examine whether strategies to reduce variability in blood pressure can effectively decrease the risk of cognitive impairment as well as of brain vascular disease.”
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Eleanor McDermid, Senior medwireNews Reporter