Morning hypertension unmasked as risk factor for cardiovascular events

Sep 8 2014

By Afsaneh Gray, medwireNews Reporter

Patients on antihypertensive medication who have high blood pressure (BP; >145 mmHg) in the morning, as measured with home monitoring kits, are at increased risk of cardiovascular events, even if their clinic measurement is acceptable, researchers have found.

“Therefore, we strongly recommend measuring and monitoring HBP [home blood pressure] in real-world clinical practice so as to identify masked hypertension, which can be described as a pitfall in the treatment of hypertension”, they write in Hypertension.

The prospective observational study of 21,591 outpatients with essential hypertension, carried out in Japan, was designed to reflect the “real-world” scenarios clinicians face when treating patients with high blood pressure.

Patients were asked to measure their own BP at home twice in the morning and twice at bedtime, with the average of these measurements across 2 days being taken at seven follow-up points between 1 week and 24 months.

After a mean follow-up period of 2.02 years, lead author Kazuomi Kario (Jichi Medical University School of Medicine, Tochigi) and colleagues report that cardiovascular events occurred in 280 patients, at an incidence of 6.46 per 1000 patient–years.

Patients with a high morning systolic HBP (≥145 to <155 mmHg) were a significant 83% more likely to have a cardiovascular event than those with a morning HBP below 125 mmHg. The risk was even greater in those with a morning HBP of 155 mmHg or above (hazard ratio [HR]=5.03).

Patients with a systolic clinic BP of 150 to 159 mmHg (HR=1.69) and 160 mmHg and above (HR=4.38) also faced an increased risk of cardiovascular events compared with those with a clinic BP below 130 mmHg.

Importantly, however, patients with a clinic BP below 130 mmHg were at an increased risk of cardiovascular events if they had a morning HBP of or above 145 mmHg (HR=2.47) compared with below 125 mmHg.

Consequently, Kario and colleagues conclude: “It is essential to control morning HBP to <145 mm Hg, even in patients with controlled clinic blood pressure.”

The morning HBP associated with minimum risk was 124 mmHg according to spline regression analysis, suggesting that further lowering of HBP may be beneficial. But the researchers warn that the structure of their study precluded the determination of a precise target blood pressure for clinicians to work towards; for this, randomized studies would be needed.

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