Reproducibility of masked hypertension determined from morning and evening home blood pressure measurements over a 6-month period

Recently, the existence of so-called masked hypertension has attracted attention. In this study, the reproducibility of masked hypertension determined from morning and evening home blood pressure measurements was examined over a 6-month period. Home blood pressure measurements were taken consecutively for 7 days in volunteers at a company in 2002 and again in 2003. The 503 Japanese subjects (329 male, 174 female, mean age: 39.4 years), who were not taking anti-hypertensive drugs, were asked to measure their home blood pressure three times every morning and three times every evening. We defined casual blood pressure ≥140 (systolic) or ≥90 (diastolic) mmHg and home blood pressure ≥135 or ≥85 mmHg as hypertension. We also defined normotension as <140 and <90 mmHg in casual blood pressure and <135 and <85 mmHg in home blood pressure. We examined the reproducibility of four blood pressure categories (normotension, hypertension, white-coat hypertension, and masked hypertension) over a 6-month period. When measured in morning home blood pressure, the reproducibility of masked hypertension (59.1%) was significantly higher than that of white-coat hypertension (25.0%) and similar to that of hypertension (67.6%). However, the reproducibility of masked hypertension (23.5%) was similar to that of white-coat hypertension (32.0%) and significantly lower than that of hypertension (66.7%) when determined using evening home blood pressure. The concordances in the four blood pressure categories between the two periods were 0.582 (κ coefficient) and 0.463 when determined using morning and evening home blood pressure data, respectively. In conclusion, the reproducibility of masked hypertension over a 6-month period was moderate in an urban Japanese population when evaluated by morning home blood pressure.