Non-dipper phenomenon in essential hypertension is related to blunted nocturnal rise and fall of sympatho-vagal nervous activity and progress in retinopathy

Although the relation between the blunted nocturnal decline in blood pressu re and target organ damages is well established, the mechanism underlying t hese results has not been clarified. We investigated the relationship among heart rate variability, nocturnal change in blood pressure and the severit y of cardiac and extracardiac target organ damages caused by essential hype rtension. We studied 52 Japanese inpatients with essential hypertension (24 men and 28 women; mean age, 49 +/- 3 years). After a stabilization period of 1 week, ambulatory blood pressure monitoring (ABPM) and 24-h ECG monitor ing were performed and analyzed. The non-dipper subjects were defined as th ose whose nocturnal decrease of mean BP was < 10% of daytime blood pressure (BP). The sex, age, body mass index, duration of hypertension, and 24-h BP were similar in dipper (n = 34) and non-dipper(n = 18) patients. The left ventricular mass index (LVMI) was significantly higher and the degree of hy pertensive retinopathy was significantly worse in the non-dipper patients t han that of the dipper patients. In the non-dipper patients, indexes of tim e-domain analysis such as the sum of differences between adjacent RR interv als (NNDrms), the number of pairs of adjacent RR intervals differing by mor e than 50 ms in the entire recording (RR 50) were significantly lower than that of the dipper patients. Additionally, as for spectral analysis. daytim e low frequency/high frequency (LF/HF) was higher and nighttime high freque ncy (HF) was lower than that of the dipper patients. Independent predictors were the 24-h mean blood pressure (MBP) For left ventricular hypertrophy ( LVH), nighttime systric BP (SBP) for progress in retinopathy and duration o f hypertension for proteinuria. In conclusion, decrease in parasympathetic nervous function and increase in sympathetic nervous function may contribut e to occurrence of non-dipper phenomenon, as well as progress in retinopath y. (C) 2001 Elsevier Science B.V. All rights reserved.