NEW YORK (Reuters Health) – Patients who monitor their own blood pressure should do so 4 times a day for at least 3 days to get the most accurate prediction of future strokes and heart attacks, according to a new study in Hypertension.
The researchers found that home monitoring was most predictive when done twice in the morning and twice in the evening for a full week – but the added predictive value after day 3 was small.
Multiple measurements account for possible daily variations in BP and paint a better picture of a patient’s true BP level, explained Dr. Teemu Niiranen and colleagues from Finland’s National Institute for Health and Welfare in Turku.
In the prospective study, 2081 adults age 45 to 74 were given home BP monitors and told to take measurements twice in the morning and twice in the evening for 7 days, recording each measurement.
Over a follow-up of 6.8 years, 162 subjects suffered a fatal or non-fatal cardiovascular event – equal to 11.5 events per 1,000 person-years. The researchers found that the predictive value of home BP measurements increased with the number of measurements taken – with most of that added predictive value happening in the first 3 days.
Morning and evening BP measurements were equally predictive of cardiovascular events, and measuring twice on each occasional improved predictive value “marginally.”
Cumulative measurements showed a HR of 1.021 (95% CI: 1.012-1.030) for systolic blood pressure and 1.034 (95% CI: 1.018-1.049) for diastolic blood pressure per 1 mmHg increase over 7 days. That compared to HRs of 1.014 (95% CI: 1.006-1.021) for SBP and 1.019 (95% CI: 1.004-1.034) for DBP after 1 day of measurements.
Dr. Niiranen and colleagues noted that more measurements mean extra time and labor required for patients, and that future studies are needed to determine which patients might be less compliant when asked to take additional readings.
Still, the authors concluded that “we feel that novel information from this study should be used to prepare a unified international guideline for home BP measurement.”
In an editorial published with the study, Dr. Lawrence Krakoff of the Mount Sinai School of Medicine in New York said that it is important to consider that variation in day-to-day BP readings may also be associated with cardiovascular disease risk.
“If variability of home pressures is indeed an important prognostic measure, enough pressure measurements will be needed for an accurate SD, as well as for the average pressure,” Dr. Krakoff wrote.
He added that home blood pressure monitoring can be “an empowering method for patients to assist in giving themselves control over their own management.”
Optimal Schedule for Home Blood Pressure Measurement Based on Prognostic Data