Morning Hypertension -MORNING BLOOD PRESSURE PREDICTS STROKE

MORNING BLOOD PRESSURE PREDICTS STROKE

CHICAGO—New studies in elderly patients suggest that hypertension in the morning hours is a strong, independent predictor of future stroke events, holding greater risk than even sustained hypertension. A second report from the same research group shows that a morning surge in blood pressure is a better predictor of stroke than extreme dips in pressure during the night. Stroke risk in the “extreme dippers” was highest only when this characteristic was combined with a morning surge in blood pressure. The reports were presented by Kazuomi Kario, MD, at the American Heart Association’s Scientific Sessions 2002.

Dr. Kario, of the Department of Cardiology at Jichi Medical School in Tochigi, Japan, reported that when he and his colleagues entered both factors—morning blood pressure levels and morning surge in blood pressure—the significance disappeared, “so I think both factors may be closely related.” That is, those persons with the greatest morning surges have the highest morning blood pressures and are at the highest risk for future stroke events.

 

DIPPERS AND NONDIPPERS

In healthy individuals, blood pressure has a diurnal pattern, falling during the night and rising during the early morning hours prior to awakening.

Abnormal diurnal patterns have been shown to occur in individuals whose blood pressure does not drop at night (“nondippers”). Nondippers have greater damage to organs including the brain, heart, and kidneys, particularly in those extreme cases in which blood pressure during sleep is actually higher than during wakefulness, a group dubbed “risers.”

Dr. Kario and colleagues had previously identified another subtype of abnormal diurnal variation, the so-called extreme dippers, who have a higher frequency of both silent and clinical cerebrovascular disease.

Extreme dippers may also have an exaggerated morning surge of blood pressure, Dr. Kario said. They have also shown that risers have the worst stroke prognosis, and extreme dippers are at an intermediate risk.

 

MORNING SURGE

In the first report presented by Dr. Kario, the researchers prospectively studied the impact of interaction between the morning surge in blood pressure and nocturnal dipping status on stroke risk in a group of 519 elderly Japanese patients with hypertension (mean age, 72) who were free of cardiovascular disease at baseline.

Cranial magnetic resonance imaging, to detect any signs of infarct, and ambulatory blood pressure monitoring were carried out at baseline. Participants were then followed a mean of 41 months for stroke events. For this analysis, transient ischemic attack was excluded as an end point, Dr. Kario noted.

The difference between each patient’s lowest night blood pressure, taken as an average of three consecutive nights, and the morning blood pressure measurement, taken two hours after waking, was calculated. Those with a greater than 55 mm Hg increase between lowest night and highest morning pressures were defined as the morning surge group, and the remainder as the non–morning surge group. Dr. Kario noted that average morning systolic pressure in the morning surge group was 175 mm Hg, in the range considered hypertense.

Participants were further classified by their nocturnal dipping status. Extreme dippers were defined as those with a decrease of 20% or more in nocturnal systolic pressures. “Dippers” had a decrease of 10% or more but less than 20%. Nondippers had a nocturnal blood pressure decrease of less than 10%, and risers had increased nocturnal systolic pressures.

During follow-up, 44 stroke events occurred. In Cox regression analysis, age, 24-hour systolic blood pressure, and morning surge status were all significantly and independently associated with stroke risk, Dr. Kario said. Each 10 mm Hg increase in systolic pressure during the morning surge was associated with a 25% increased risk of stroke. When nocturnal dipping status was added to the model, the researchers found risers also had an increased risk of stroke, but extreme dippers did not have an increased risk unless they also fell into the morning surge group.

The investigators also found that 78% of the stroke events in the morning surge group occurred between 6 am and noon, compared with 41% in the non– morning surge group, a significant difference.

“An excessive morning surge was an independent predictor of stroke in elderly patients with hypertension,” Dr. Kario concluded. “This extends our previous work showing that extreme dippers are at an increased risk of stroke, and this mechanism may be the morning surge, rather than excessive low blood pressure at night.” He added that his group found no predominance of stroke type during the morning period. If the surge in blood pressure directly triggered the stroke, then hemorrhagic stroke should probably predominate—but this was not the case. Dr. Kario speculated that in ischemic events, the surge in blood pressure may trigger platelet hyperaggregation.

 

MORNING HYPERTENSION

In his second report, Dr. Kario presented data from another analysis carried out in the same cohort. Here, the risk for stroke among patients with morning hypertension was compared with that seen with increased blood pressure at other times of the day.

Morning blood pressure, evening blood pressure, and pre-awake blood pressure were defined as the average of blood pressures during the first two hours after wake-up time, before going to bed, and just prior to wake-up time, respectively.

After controlling for age, sex, body mass index, smoking, diuretics, hyperlipidemia, silent cerebral infarct, and antihypertensive medication status, morning blood pressure was the strongest independent predictor for stroke among clinic, 24-hour, awake, sleep, evening, and pre-awake readings, Dr. Kario reported.

Each 10 mm Hg increase in morning blood pressure was associated with a 44% increase in the risk of stroke. The difference between morning and evening blood pressures was also independently associated with stroke risk, with each 10 mm Hg increase associated with a 24% increase in stroke.

Finally, the researchers defined sustained hypertension as having an average morning-to-evening blood pressure of 135 mm Hg or greater and a difference between morning and evening measures of less than 20 mm Hg. Morning hypertension was defined as an average of 135 mm Hg or greater and a morning to evening difference of more than 20 mm Hg. When they compared these groups, the adjusted stroke risk was significantly higher in subjects in the morning hypertension group.

“In conclusion, in older patients with hypertension, morning blood pressure is the best predictor for stroke among ambulatory blood pressures during other periods,” Dr. Kario said. “The difference between the morning blood pressure and evening blood pressure was also associated with stroke risk independently of 24-hour blood pressure level. The morning blood pressure should be first monitored in home blood pressure monitoring in patients with hypertension,” he added.

 

http://www.neurologyreviews.com/mar03/mar03_bloodpressure.html

 

ischemia : : deficient supply of blood to a body part (as the heart or brain) that is due to obstruction of the inflow of arterial blood

 from ischein to restrain (akin to Greek echein to hold) + haima blood