Variability in SBP portends cognitive decline

Findings from the Ohasama study reveal an association between variability in home systolic blood pressure (SBP) and cognitive decline.

The association was independent of SBP per se, which itself did not predict cognitive decline independently of SBP variability, report Takayoshi Ohkubo (Teikyo University School of Medicine, Tokyo, Japan) and team in Hypertension.

The team’s analysis included 485 Ohasama study participants who did not have cognitive decline at baseline, defined as a Mini-Mental State Examination score lower than 24. These participants, who were aged an average of 63 years, measured their home BP every morning for 4 weeks.

After a median follow-up of 7.8 years, 9.5% of the participants had developed cognitive decline. This risk rose significantly across tertiles of SBP and SBP variability, defined as the standard deviation (SD) of SBP.

When analysed as a continuous variable, each SD increase in SBP was associated with a significant 48% increase in the risk of cognitive decline. And each SD increase in SBP variability was associated with a 51% increased risk, even after accounting for average SBP. Conversely, adjusting for SBP variability weakened the association between home SBP and cognitive decline to the point of nonsignificance.

When SBP and the SD of SBP were dichotomised at the median (124.7 and 8.6 mmHg, respectively), participants with both values at or above the median had a 6.40-fold increased risk of cognitive decline relative to those with both values below the median. Participants with increased SD of SBP only had a still significant 4.89-fold risk increase, while those with increased SBP only had a nonsignificant 2.79-fold increase.

In an accompanying editorial, Paolo Palatini (University of Padova, Italy) says that, based on recent findings, careful choice of antihypertensive regimen could reduce BP variability and therefore improve cerebral outcomes. However, he also points out that this would be “a fruitless exercise” if BP variability “is simply a marker of an underlying chronic illness”.

Palatini says that progressing dementia could damage areas of the brain involved in BP regulation, leading to BP variability, or that it could arise from large-artery stiffness or cardiovascular autonomic dysfunction.

He concludes: “Only future long-term clinical trials encompassing the current main classes of antihypertensive drugs will reveal whether different drug classes have a different action on BP [variability] and whether reduction of day-by-day BP [variability] may help to prevent or delay cognitive decline in hypertension.”

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