Early morning-Best time window of hourly 24-hour ambulatory blood pressure in relation to hypertensive organ damage: The Japan Morning Surge-Home Blood Pressure study.

The correlations between organ damage and hourly ambulatory blood pressure (BP) have not been established. The patients were 1464 participants of the Japan Morning Surge-Home Blood Pressure (J-HOP) study participants who underwent ambulatory BP monitoring. The hourly systolic BP (SBP) at x o'clock was defined as the average of SBP values measured at times x - 30 minutes, x, and x + 30 minutes. The mean age was 64.8 ± 11.6 years. The percentage of male participants was 47.8%. The left ventricular mass index (LVMI) was significantly associated with SBP at 6 o'clock (r = 0.166, P < 0.001). The carotid intima-media thickness was significantly associated with SBP at 5 o'clock (r = 0.196, P < 0.001). After adjustment for age, sex, smoking, hyperlipidemia, diabetes mellitus, antihypertensive drug use, clinic SBP, and 24-hour ambulatory SBP, the correlations of the LVMI and hourly SBP at 6 o'clock remained significant (beta coefficient = 0.125, P < 0.01). In conclusion, morning ambulatory systolic BP especially at 5 and 6 o'clock was independently associated with organ damage.