People are living longer than ever, making it important to find ways to prevent or delay cognitive decline in older adults. Keeping blood pressure under control seems to be one way to do this.

High blood pressure, or hypertension, has been associated with a decline in cognitive function and an increased risk of Alzheimer's disease.

Lifestyle modifications, such as quitting smoking and reducing salt, and medications can help people control their blood pressure, but older adults can still experience variations in their systolic — the top number of a blood pressure reading — and diastolic (the bottom number) blood pressure.

Participants with the greatest variability in their systolic blood pressure were almost two years older in cognitive age than those with the least systolic blood pressure variability.

The possibility that variations in blood pressure might be linked to cognitive decline has been studied in older white adults, but few studies have considered older Black adults. Nor have variations in blood pressure and cognitive decline in white adults been compared to that of Black adults.

To gain a better understanding of these relationships and the possible racial and socioeconomic factors affecting them, the researchers at Rush University in Chicago enrolled a predominantly Black study population.

They found that greater variability in systolic or diastolic blood pressure was associated with lower scores on standardized tests of cognitive function in both Black and white adults 65 years old and older. “These findings highlight the importance of monitoring and controlling blood pressure in older adults,” Anisa Dhana, lead author on the study, told TheDoctor in an email.

The association between blood pressure variability and cognitive function was significant only in Black adults. Dhana pointed out that although the results replicate the findings of past studies done in white adults, the current study population was 66 percent Black.

The significance of this association in Black participants was likely due to racial differences in hypertension treatment and socioeconomic factors compared to white participants, Dhana, a physician and postdoctoral researcher at Rush University in Chicago, said.

Black participants had less education, got less physical activity and were more likely to smoke than white participants. They also had more comorbidities and were less likely to take antihypertensive medication, the researchers found. “These findings provide more evidence of the higher rate of vascular risk factors in Black communities,” they said.

The 4,770 study participants were enrolled in the Chicago Health and Aging Project, a population-based, observational study. The average age of participants was 71. High blood pressure, or hypertension, is defined as 138/80 mm Hg or above. Participants' average blood pressure was 138/78 mm Hg. Blood pressure was measured every three years for about 10 years during the 18-year study.

Participants were divided into three groups based on how much their blood pressure varied over time. Variability of systolic blood pressure and diastolic blood pressure was calculated as the sum of the absolute difference between successive blood pressure measurements divided by the number of previous visits.

Black participants with the greatest systolic blood pressure variability were almost three years older in cognitive age than Black participants with the least systolic blood pressure variability.

The average variation in systolic blood pressure was 17.7 mm Hg among Black participants and 16.0 mm Hg among white participants.

Participants with the greatest variability in their systolic blood pressure were almost two years older in cognitive age than those with the least variable systolic blood pressure. Black participants with the greatest systolic blood pressure variability were almost three years older in cognitive age than Black participants with the least systolic blood pressure variability. The results were similar for diastolic blood pressure variability.

It is important to keep in mind that while these findings demonstrated an association between blood pressure variability and cognitive function, they did not prove causality.

The study is published in Neurology, the medical journal of the American Academy of Neurology.