By AMERICAN HEART ASSOCIATION NEWS

In a study of older Japanese people, large variations in blood pressure readings during home monitoring were associated with a higher risk of all types of dementia, including Alzheimer’s disease.

“Home monitoring of blood pressure may be useful to assess the future risk of dementia,” said  lead study author Tomoyuki Ohara, M.D., Ph.D., an assistant professor of neuropsychiatry at the Graduate School of Medical Sciences at Kyushu University in Fukuoka City, Japan.

Previous studies reported a heightened risk of cognitive impairment and dementia in people with large variations in blood pressure from one doctor visit to another, but this study, published Monday in the American Heart Association’s journal Circulation, is the first to use home monitoring to examine the association between blood pressure variability and dementia risk.

Home monitoring may be more reliable than office measurements because of the “white-coat” effect, in which some people have higher blood pressure in the doctor’s office than they do at home.

Researchers asked more than 1,600 Japanese adults with an average age of 71, without dementia, (56 percent female) to measure their blood pressure at home for one month. On average participants measured their blood pressure three times each morning prior to eating breakfast or taking medication. Participants included both those with normal and high blood pressure. About four  in 10 were taking medication for high blood pressure. Researchers reviewed the month of home blood pressure readings, conducted cognitive testing to uncover the development of dementia and reviewed records for the occurrence of stroke.

During the five-year follow-up, 134 subjects developed Alzheimer’s disease and 47 developed vascular dementia, which results from diminished blood flow to the brain and is often related to the occurrence of small strokes.

Compared with participants who had the most stable blood pressure, and after adjusting for other dementia risk factors and the average blood pressure levels themselves, those with the highest variability in systolic (higher number) blood pressure were:

  • more than twice as likely to develop any type of dementia or Alzheimer’s disease; and
  • nearly three times more likely to develop vascular dementia.

In addition, among participants with greater blood pressure variability, higher systolic blood pressure further increased the risk of vascular dementia but did not change the heightened risk of Alzheimer’s disease.

“Further studies are needed to clarify whether day-to-day blood pressure variation is an indicator of future dementia, or whether it might be a target for interventions aimed at preventing dementia,” Ohara said. “Blood pressure variation may indicate high blood pressure that is inadequately treated, but other factors, such as mental or physical stress, sleep deprivation, an irregular lifestyle, or damage to nerves that control involuntary bodily functions, can also contribute.”

Participants in this study were part of the large, ongoing Hisayama Study, which has tracked for decades the health and cognitive performance in adult residents of a suburb of Fukuoka City, Japan. Because the study population was Japanese, the findings may not apply to a Western population or to other ethnic groups with different lifestyles or genetic backgrounds.