New study from Japan suggests that if your blood pressure varies from day-to-day, you may be at higher risk for dementia or Alzheimer's disease.

Blood Pressure Fluctuations tied to Dementia Risk

People whose systolic blood pressure (the top reading) fluctuated from day-to-day were more than twice as likely to develop any type of dementia or Alzheimer's disease compared to those with more stable day-to-day blood pressure, the researchers found. And the study -- which was based on home-monitorings -- also reported that the participants were nearly three times more likely to develop vascular dementia, caused by hardening of the arteries.

"Our main findings suggest that increased day-to-day blood pressure variability, independent of average home blood pressure, is a significant risk factor for the development of all-cause dementia, vascular dementia and Alzheimer's disease in the general elderly Japanese population," said lead researcher Dr. Tomoyuki Ohara. He's an assistant professor of neuropsychiatry at the Graduate School of Medical Sciences at Kyushu University in Fukuoka City.

The association between daily blood pressure fluctuations and dementia was seen whether participants had normal or high blood pressure, he added.

But Ohara cautioned that this study doesn't prove that variations in blood pressure cause dementia, only that the two appear to be associated.

However, if you have fluctuating blood pressure, stabilizing it might help prevent dementia, he said.

For the study, participants measured their blood pressure three times every morning for a month to track daily variations.

"It could be important to have a daily habit of measuring one's own home blood pressure," Ohara said. "However, further studies are needed to clarify whether day-to-day blood pressure variation is an indicator of future dementia or a medical target for the prevention of dementia," he said.

The report was published online Aug. 7 in the journal Circulation.

Dr. Costantino Iadecola is director of the Feil Family Brain and Mind Research Institute at Weill Cornell College of Medicine in New York City.

"Using home blood pressure monitoring, these researchers really nailed down the connection between blood pressure variations and the risk for dementia," he said.

"There is no question that blood pressure has an effect on the blood vessels in the brain," he added.

Individuals whose blood pressure fluctuates might be treated to minimize the fluctuations, which in turn might keep the blood vessels in the brain healthy, Iadecola said.

"For this to become relevant, it may help to monitor blood pressure for an extended period of time," said Iadecola, who coauthored an accompanying editorial in the journal.

"Then we may be able to identify patients who would benefit from leveling off blood pressure," he said. "There is mounting evidence that this is what we need to be doing."

Iadecola said the time to get blood pressure stabilized is not when you're old, but in midlife when dementia begins to develop.

"Healthy vessels, healthy brain, healthy mind," he said. "If the vessels of the brain work, the brain is going to work fine, and if the brain works fine, your mind is going to be sharp."

For the study, Ohara and colleagues looked at more than 1,600 Japanese men and women 60 and older who did not have dementia. The group included those with normal and high blood pressure. About 40 percent were taking medication to lower their blood pressure.

The participants measured their blood pressure three times at home in the morning for one month. Ohara's team reviewed the month of home blood pressure readings, and looked for signs of dementia through memory and thinking tests. They also reviewed participants' medical records to see if a stroke had occurred.

Over five years of follow-up, 134 individuals developed Alzheimer's disease and 47 developed vascular dementia, the researchers found.

Vascular dementia results from diminished blood flow to the brain and is often related to the occurrence of small strokes, the researchers said.

The editorial authors noted that there were several limitations to the study. One is that blood pressure can be variable on its own. Blood pressure readings tend to change if you're sick or if you've taken certain medications. Taking blood pressure medications inconsistently -- for example, forgetting the medication one day -- can also change day-to-day readings.

The research also needs to be replicated in a larger and more diversity of people, based on the editorial authors' comments.