August 11, 2017
Large variations in day-to-day home blood-pressure readings were tied to an increased risk of future Alzheimer's disease, independent of high systolic blood pressure, in a new study. Having both factors predicted an increased risk of vascular dementia.
In this study of Japanese individuals who were 60 or older and measured their blood pressure each morning for a month, those with the most variable readings had more than twice the risk of being diagnosed with vascular dementia or Alzheimer's disease within 5 years vs those with stable readings.
These results, by Dr Emi Oishi (Kyushu University, Fukuoka City, Japan) and colleagues, were published August 7, 2017 in Circulation.
The findings suggest that adequately treating hypertension and maintaining a healthy lifestyle with low mental or physical stress and good sleep habits "could contribute to lower the blood-pressure variability, which might then lead to reduced risk of dementia," senior author Toshiharu Ninomiya, MD (Kyushu University) told theheart.org | Medscape Cardiology in an email.
However, these are hypotheses, he cautioned, and whether blood-pressure variability is a modifiable risk factor for dementia or Alzheimer's disease needs to be confirmed in further study.
In an accompanying editorial, Drs Alexander E Merkler and Constantino Iadecola (Weill Cornell Medical College, New York, NY) agree. "If confirmed in a larger cohort, these findings may guide future prospective studies aimed at curtailing the risk of dementia by reducing" blood-pressure variability, they write.
"I think this is an important study," American Heart Association spokesperson Dr Mary Ann Bauman (Seattle, Washington) told theheart.org | Medscape Cardiology.
It "gives us information that not only will help physicians but will also help patients understand the importance of maintaining their blood pressure under control" with stable readings, she said, adding, like the others, that further research is needed including study in other populations.
Day-to-Day BP and Future Dementia
Several studies have reported that having greater variations in visit-to-visit blood-pressure readings in a doctor's office increases the risk of future cognitive impairment and dementia, but these measurements may be less accurate due to "white-coat" hypertension.
While 48-hour ambulatory blood-pressure readings may provide a truer measure of fluctuations, they note, this method is cumbersome.
Instead, Oishi and colleagues aimed to study the relationship between fluctuations in blood-pressure readings taken using a blood-pressure cuff at home each morning for a month and the risk of future vascular dementia and Alzheimer's disease.
They identified 1674 individuals in the Hisayama Study who were at least 60 years old in 2007 and free of dementia, who agreed to participate.
The subjects (738 men and 936 women) were instructed to measure their blood pressure three times after more than 5 minutes of rest, within an hour of getting up and before having breakfast or taking any medication, for 4 weeks.
All participants were given the same digital electronic device (HEM-70801C, Omron Healthcare) based on the cuff oscillometric method. Almost all (99%) provided readings for 28 days.
At baseline, the subjects had a mean age of 71 and a mean blood pressure of 138/77 mm Hg, and 43% were taking an antihypertensive agent.
The patients were divided into quartiles based on their day-to-day variations in systolic and diastolic blood pressure.
Dementia diagnoses were adjudicated by neurologists or psychiatrists and based on clinical information, neuroimaging (in 95% of cases), and brain autopsy (in 21 cases).
During a median follow-up of 5.3 years, 194 patients (72 men and 122 women; 11.6%) developed all-cause dementia, of whom 47 had vascular dementia and 134 had Alzheimer's disease.
The age- and sex-adjusted incidence of all-cause dementia, vascular dementia, and Alzheimer's disease increased with increasing levels of variation in both systolic and diastolic blood pressure.
Patients with the highest vs lowest variability in blood pressure had a significantly higher risk of developing Alzheimer's or vascular dementia during follow-up.
It is not clear whether blood-pressure variability is a modifiable risk factor for dementia, Ninomiya said. Variations in blood pressure may cause changes in brain structure and function that lead to the development of dementia, he noted. On the other hand, blood-pressure variability may simply be a marker of nonmodifiable neurodegeneration. Further studies are needed to explore this.
In the meantime, "we could say that the patients with greater blood-pressure variabilities should avoid poor adherence to medication and an unhealthy lifestyle," because these are known causes of blood-pressure variability.
The authors and editorialists have no relevant financial relationships.