Cumulative blood pressure load and cognitive decline in older adults: An observational analysis of two large cohorts

Abstract

Introduction: Cumulative blood pressure metrics may provide greater precision for measuring temporal risk exposure, especially in later life where data are mixed regarding associations of high blood pressure (BP) on cognitive function. We examined the relationship between greater cumulative exposure to high BP in later life and several domains of cognitive function.

Methods: Individual cognitive assessment scores and BP measurements in older adults (age ≥70 years) at baseline and over approximately 8 years of follow-up were available in the population-based Canadian Victoria Longitudinal Study (VLS) and Swedish Gothenburg H70 Birth Cohort Studies (H70). Linear mixed models were used to quantify associations between cumulative systolic and diastolic BP and change in cognitive scores.

Results: Each additional 100mmHg increase in cumulative BP was related to greater decline in the Rey Auditory Verbal Learning Test (RAVLT) List A, trials 1-5 total score over follow-up: -0.23 (95% confidence interval [CI] -0.32, -0.13) for systolic BP and -0.41 (95%CI -0.58, -0.23) for diastolic BP. Similarly increases cumulative systolic and diastolic BP were related to greater declines Digit Symbol Substitution Task (DSS) scores: -0.59 (95%CI -0.80, -0.38) and -1.04 (95% CI -1.40, -0.67), respectively. There were no associations of cumulative BP and temporal changes in general cognition, other measures of verbal episodic memory, or semantic fluency.

Conclusions: Higher cumulative BP is associated with greater declines in RAVLT measured immediate memory span and complex attention, information processing speed and visuospatial scanning in older adults, but the scale of change is small. Additional research is required to further define these relationships and identify opportunities for prevention.

Plain Language Summary

Researchers are continuing to explore how vascular health (such as sustained high or low blood pressure) can affect various important characteristics of aging individuals. These characteristics affected by vascular health include specific brain and cognitive aging changes, as well as risk for dementia. In this study, we examined how long-term exposure to high blood pressure, which is quite common in aging persons, can affect cognitive changes in older adults. A unique feature of this international study is that it was conceived by our Australian colleagues and was conducted on two separate databases of brain and cognitive aging persons. One of these databases was a Canadian project (Victoria Longitudinal Study), which has partnered with CCNA researchers frequently. The other project was the Swedish Gothenburg Cohort Study. The two large-scale studies had sufficient similarities and very rich relevant datasets to provide a unique opportunity to conduct to parallel analyses and compare the results. Our results suggested that among Canadian and Swedish older adults, the effects of long-term high blood pressure on cognitive changes are subtle but detectable. Further research is recommended, including examination of clinical outcomes such as dementia.