Short-term and long-term repeatability of the morning blood pressure in older patients with isolated systolic hypertension

OBJECTIVE: Using 24-h ambulatory blood pressure monitoring, we studied the repeatability of the morning blood pressure in older (=60 years) patients with isolated systolic hypertension. METHODS: The sleep-through morning surge was the morning blood pressure minus the lowest nighttime blood pressure. The preawake morning surge was the morning blood pressure minus the preawake blood pressure. In addition, we determined the cusum plot height of blood pressure from 04:00 to 10:00 h from a plot of cumulative sums. RESULTS: In 173 patients with repeat recordings within 33 days (median), the short-term repeatability coefficients, expressed as percentages of maximal variation, ranged from 35 to 41% for the daytime and nighttime blood pressures and from 50 to 56% for the night-to-day blood pressure ratios. Short-term repeatability ranged from 52 to 75% for the sleep-through and the preawake morning surge, and from 51 to 62% for the cusum plot height. In 219 patients with repeat recordings within 10 months (median), the corresponding long-term estimates ranged from 45 to 64%, from 69 to 71%, from 76 to 83%, and from 50 to 78%, respectively. In categorical analyses of the short-term repeatability of the sleep-through morning surge and the preawake morning surge, using the 75th percentile as arbitrary cut-off, surging status changed in 28.0 and 26.8% of patients (κ-statistic ≤0.33). In the long-term interval, these proportions were 32.0 and 32.0%, respectively (κ-statistic ≤0.20). The κ-statistic threshold for moderate reproducibility is 0.4. CONCLUSION: The morning surge of blood pressure is poorly reproducible, irrespective of whether it is analysed as continuous or categorical variable. © 2008 Lippincott Williams & Wilkins, Inc.