BLOOD-PRESSURE LEVEL AND VARIABILITY IN THE PREDICTION OF BLOOD-PRESSURE AFTER 5-YEAR FOLLOW-UP

We compared mean intra-arterial ambulatory blood pressure (IAMB), bloo d pressure (BP) diurnal profiles and variability, and postural measure ments with casual sphygmomanometric measurements for the prediction of future BP. We studied 97 healthy, unmedicated men classified as normo tensive (NT, n = 34). borderline hypertensive (BHT, n = 29), or mildly hypertensive (HT, n = 34) by repeated casual measurements during the 2 months before IAMB. Five years later, we reassessed 79 subjects (81% ) using casual BP measurements and noninvasive ambulatory 24-hour BP m onitoring (NAME). IAMB level generally correlated well with follow-up BP and slightly better with NAME level than with casual measurements ( 24-hour IAMB versus follow-up NAME systolic BP [SEP], r = .64, P < .00 1; versus diastolic BP [DBP], r = .52, P < .001). NT and BHT subgroup correlations were of similar strength, but the relationship in the HT subgroup was not significant. Similarly, when we examined daytime and nighttime BP levels, nighttime BP correlated better with follow-up BP in NT and BHT but not in HT. The only measures that were significantly related to follow-up BP in HT were two BP variability measures, SD an d the range of variability (RV(80): 90th minus 10th percentile) (initi al 24-hour IAMB SD and follow-up BP, r = .42 to r = .52, P < .05 to P < .01; RV(80) versus follow-up BP, r = .43 to r = .52, P < .05 to P < .01). Correlations of follow-up BP with postural BP were generally wea ker than with casual BP or IAMB level. Linear stepwise regressions for SEP and DBP separately (including all IAMB variables) demonstrated th at the best single predictor for follow-up BP was 24-hour IAMB SEP lev el, which explained 41% of follow-up NAME SEP level variance (F = 52.6 , P < .001). However, in a second analysis including casual values, ca sual SEP alone explained 44% of follow-up NAME SEP variance (F = 62.5, P < .001), whereas IAMB SEP added only 4% (F = 5.5, P < .05). Predict ions of follow-up DBP were always poorer. After 5 years, 70% of NT and 86% of HT were still in their initial classification group, but 67% o f BHT had become hypertensive. In these new HT (n = 16), initial IAMB level correlated most strongly with follow-up NAME level (24-hour SEP, r = .70, P < .01; 24-hour DBP, r = .55, P < .05). The only other sign ificant demographic variable predicting future BP was change in weight over 5 years, which added 10% to the explanation of future casual Ssp variance (F = 12.5, P = .0007) and 15% to casual DBP variance (F = 18 .0, P = .0001); for NAME, the percentages were lower. In logistic regr ession, those NT and BHT who became hypertensive (n = 22) had a 75% pr obability of becoming hypertensive if they gained 11.7 kg or more duri ng 5 years (chi(2) = 4.5, P = .03). To conclude, BP tended to increase in all groups, especially in BHT, during follow-up. Nominal differenc es were observed between casual measurements and BP level measures in the prediction of future BP, and their explanatory value for future BP was generally less than 50%. However, for BHT who became hypertensive , BP level and variability measurements somewhat improved the predicti on of follow-up BP. Weight gain was an important additional predictor for future hypertension in both NT and BHT.