AMBULATORY INTRAARTERIAL BLOOD-PRESSURE IN ESSENTIAL-HYPERTENSION - EFFECTS OF AGE, SEX, RACE, AND BODY-MASS - THE NORTHWICK PARK HOSPITAL DATABASE STUDY

Twenty-four-hour recordings of intraarterial blood pressure (IABP) fro m 723 untreated hypertensive patients were analyzed for the effects of age, sex, race, and body mass index on the level of IABP and its circ adian variation. Age had a highly significant positive relationship (P <.001) with the cuff systolic and diastolic blood pressures, with reg ression coefficients (SE) of +0.83 (0.07) and +0.24 (0.04) mm Hg/year, respectively. There was a similar (P <.001) positive relationship bet ween age and 24-h mean systolic IABP, measuring +0.71 (0.07) mm Hg/yea r, but 24-h mean diastolic IABP did not increase significantly with ag e. There was a significant (P <.001) inverse relationship between age and 24-h mean heart rate (HR), at -0.17 (0.03) beats/min/year. Nocturn al fall in systolic and diastolic IABP, calculated as the difference b etween daytime and nighttime mean IABP, had a significant (P <.001) ne gative relationship with age. Nocturnal fall in HR, calculated similar ly, also significantly (P < .001) decreased with age. Age did not affe ct long-term systolic and diastolic IABP variability but did decrease long-term HR variability significantly (P <.001). Hypertensive men and women of similar age, had comparable daytime mean systolic and diasto lic IABP (P=.15 and P =.03 respectively), but women had significantly (P <.001) lower nighttime mean systolic and diastolic IABP than men. T he nocturnal fall in systolic and diastolic IABP was significantly (P <.002) greater in women as compared to men. Women also had significant ly (P <.01) greater long-term systolic and diastolic IABP variability than men. Women had significantly (P <.001) greater 24-h, daytime mean and nighttime mean HR than men. Twenty-four-hour, daytime and nightti me mean IABP were all significantly higher (P <.01) in Afro-Caribbeans as compared to whites and Asians. No significant differences were obs erved in the magnitude of nocturnal IABP fall or long-term IABP variab ility between the three races. Asians and Afro-Caribbeans had signific antly (P <.001) lower nocturnal HR falls and long-term HR variability (P <.01) than whites. Body mass index (BMI) did not relate directly to the level of daytime blood pressure, clinic cuff, or daytime mean IAB P, in either men or women. BMI did have a highly significant (P <.001) positive relationship with nighttime mean IABP in men, but not in wom en. The degree of nocturnal fall of IABP had a significant (P <.001) i nverse relationship with BMI in hypertensive men.