"These data provide the first step in showing an association between diastolic blood pressure variability (DBPV) and cognition in an Australian population," Dr. Ruth Peters of Neuroscience Research Australia in Sydney and Dr. Phillip Tully of the University of New England in Armidale, NSW told Reuters Health in a joint email. "The next steps are to investigate causality."
"At the moment, we can say that if blood pressure variability is observed it might indicate an elevated risk of declining cognitive function," they said.
As reported in Hypertension, Drs. Peters, Tully and colleagues investigated the relationship between repeated (visit-to-visit) blood pressure measures and change in cognitive performance over 12 years, as well as imaging data over the same period. The data were derived from two cohorts, one midlife (40s) and one later life (60s).
BP visit-to-visit variability was calculated using all measurements during follow-up and included the standard deviation (SD) of the mean systolic BP, DBP, and pulse pressure over the duration of follow-up.
Data on cognitive change were available for 1,054 at midlife (baseline age, 42.7) and 1,233 in later life (baseline age, 62.5). Imaging data were available for 168 and 233, respectively.
In the 40s cohort, no clear patterns emerged in relationships between BP, change in BP, BPV and cognitive performance.
In the 60s cohort, no relationships were seen between BP or change in BP and change in cognitive performance.
However, after adjustment for multiple factors - including patient demographics, lifestyle factors, and antihypertensive or cholesterol medication - greater DBPV in the 60s cohort was associated with a −1.95 point decline on the symbol digit modalities test and a −0.42 point decline in performance on the Purdue pegboard using the dominant hand.
Further, for the 60s cohort only, there were relationships between BPV and white matter hyperintensity volume (WMHV) that remained after false discovery rate (FDR) adjustment.
Specifically, for DBP, a 0.1 unit greater coefficient of variability over the 12 years of follow-up was associated with a 37% greater WMHV. A higher SD in DBP was also associated with a greater WMHV (50% increase per 10 mm Hg increase in SD) after FDR adjustment.
The authors conclude in their paper, "In a largely normotensive/mildly hypertensive population, our analyses reported no relationships between blood pressure and cognition in midlife but a potential role for diastolic blood pressure variability in later life as a risk marker for cognitive decline. This may indicate an at-risk period or a means to identify an at-risk population at the age where diastolic pressure is starting to decline."
Drs. Tully and Peters added in their email, "Risk factors for blood pressure variability are currently under-researched. We need a better understanding of how different blood pressure levels and blood pressure variability might impact cognition, the role of demographics and other health parameters, and the causal pathways."
Dr. Geir Selbaek, Research Director, Ageing and Health at Oslo University Hospital and professor, faculty of medicine at Oslo University, commented on the study in an email to Reuters Health, "Even though midlife hypertension is well established as a risk factor for dementia, the timing and pattern of the risk are not well understood."
"The findings of an association between diastolic blood pressure variability and risk of cognitive decline are new and potentially important, but need to be replicated," he said. "The magnitude of cognitive decline is rather small, the interval between blood pressure measures is long and it is surprising that other well-established associations between blood pressure and cognitive decline were not found in this cohort."
"We need more representative population studies on the trajectories of blood pressure in a life-course perspective," he said. "Nonetheless, this study strengthens the recommendation about regular monitoring of blood pressure, especially in the transition between midlife and late life."
SOURCE: https://bit.ly/36SKm5C Hypertension, online February 18, 2022.
By Marilynn Larkin
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