Fluctuations in blood pressure from midlife to end-of-life: Correlation with dementia risk

In a recent study published in JAMA Network Open, researchers assess the link between year-to-year blood pressure variability (BPV) at different life stages and the risk of developing dementia in community-dwelling seniors.

Study: Year-by-Year Blood Pressure Variability From Midlife to Death and Lifetime Dementia Risk. Image Credit: pikselstock / Shutterstock.com

Background 

Hypertension during midlife can increase the risk of dementia. Although treating high blood pressure (BP) might reduce this risk, the exact relationship between the two health conditions remains unclear.

As individuals age, hypertension might even lower the risk of dementia. BP variability over time has been attributed to greater risks of heart disease and death. Research on its relation to dementia has produced mixed results, with most studies focusing on variability in later life.

A recent study suggests that fluctuating BP might pose a greater dementia risk than consistent high pressure. This relationship may change with age, gaining significance in older individuals.

Thus, further research is essential to clarify the age-dependent relationship between BP variability and dementia risk.

About the study 

Researchers from the United States-based Adult Changes in Thought (ACT) study explored the link between BPV and dementia in participants over 65 years of age from Kaiser Permanente Washington (KPW) in Seattle, Washington. The researchers also examined individuals whose brains were analyzed post-mortem through a donation program.

By accessing the detailed BP and medical histories from KPW archives, the researchers gathered consistent yearly systolic BP (SBP) measurements from age 50 onwards. BPV was then determined for each decade of the participants’ lives, excluding those with insufficient data for any given decade.

Dementia detection involved the Cognitive Abilities Screening Instrument, followed by comprehensive evaluations for those scoring below a set threshold. Dementia diagnoses were based on established medical criteria. Other health-related data, including a history of strokes and heart attacks, were also incorporated.

Using statistical analyses, the relationship between BPV and the onset of dementia was studied. Various models adjusted for factors like average BP, sex, and medical history.

Sensitivity analyses explored potential biases, cardiovascular event implications, and autopsy participant selection influences.

All statistical results with a two-sided P-value below 0.05 were considered significant. The analysis period spanned from March 2020 to September 2023.

Study findings

The present study encompassed a total of 820 participants, including 344 males and 476 females. The average age of the participants at enrolment was 77 years with a standard deviation (SD) of 6.7 years.

During the study, a mean of 28.4 yearly SBP measurements were obtained for each participant over an average period of 31.5 years. This resulted in a total follow-up time of 32.2 years in 27,885 person-years from midlife until death.

A diagnosis of all-cause dementia was evident in 372 participants, which was 45.4% of the study group. The number of individuals who were alive and did not have dementia during different BPV periods varied.

As participants aged, their mean SBP and BPV increased. More specifically, SBP rose from 131 mm Hg at 60 years to 141 mm Hg at 90 years. BPV expanded from 9.31 at age 60 to 11.22 at age 90. The incidence of dementia in their remaining lifetime ranged from 32.1% between 80-89 years of age to 46.2% in the 50-59 age group.

Higher BPV did not correlate with an increased dementia risk at the ages of 60, 70, and 80. However, at the age of 90, a one SD increase in BPV was linked to a 35% elevated risk.

Similarly, for mortality rates, there was no significant association at the ages of 60 and 70. However, at 80 and 90 years of age, the same increment in BPV suggested a 14-16% heightened mortality risk.

When combining dementia and mortality outcomes, the associations were neutral for ages 60 and 70 but indicated 9% and 19% increased risks at ages 80 and 90, respectively.

Further analyses of mean SBP did not show any strong associations; however, varying dementia risks were observed across ages. For example, at age 60, there was a 7% increased risk per SD, which became neutral by age 70 and reduced by 10% and 18% at ages 80 and 90, respectively. SBP did not show any correlation with mortality.

Subgroup and sensitivity tests provided no significant deviations from the main findings. Notably, a certain analysis found that dementia hazard ratios for BPV at age 90 were greater for long-term than short-term intervals.

When evaluating the association between BPV and SBP with elevated dementia risk, the findings were nonlinear and inversely linear, respectively. These relationships appeared to evolve with age.