Even mild depression is associated with among-day blood pressure variability, including masked non-dipping assessed by 7-d/24-h ambulatory blood pressure monitoring.

The effect of mild depression on blood pressure (BP) was assessed in 116 Japanese (32-79 years). As compared to non-depressive (Geriatric Depression Scale, GDS-15 score <5) subjects, mild depressives (GDS-15 score: 1-15) had shorter sleep duration (p = 0.021), lower subjective quality of life (health: p = 0.016; life satisfaction: p < 0.001; and happiness: p < 0.001), and higher 7-d systolic BP (p < 0.05). "Masked non-dipping" (dipping on day 1, but non-dipping on at least 1 of the following 6 d) was more frequent among depressive than non-depressive normotensives (p = 0.008). Among-day BP variability may underlie cardiovascular disease accompanying a key component of psychological depression.

Does exposure to an artificial ULF magnetic field affect blood pressure, heart rate variability and mood?

The aim of this study was to determine whether an artificial magnetic field with an amplitude and frequency equivalent to those of geomagnetic pulsations during geomagnetic storms could affect physiology and psychology. Three healthy volunteers wore anambulatory BP monitor and an ECG recorder around the clock for 12 consecutive weekends in Winnipeg, Manitoba, Canada. In a room shielded against ELF and VLF waves, they were exposed for 8 hours per week to either a 50 nT 0.0016 Hz or a sham magnetic field at one of six circadian stages. Real exposure randomly alternated with sham exposure. They provided saliva and recorded mood and reaction time every 4 hours while awake. Systolic (S) and diastolic (D) blood pressure (BP), and heart rate (HR) were recorded every 30 minutes. Spectral analysis of HR variability (HRV) was performed using the maximum entropy method and a complex demodulation method. For these variables, daily means were compared between real and sham exposure, using paired t-tests. Their circadian MESOR, amplitude, and acrophase were analyzed and summarized using single cosinor and population-mean cosinor. Circadian rhythms were demonstrated for HR, SBP, DBP for sham exposure, salivary flow rate, positive affect, vigor, and subjective alertness (p < 0.001, -0.02). One participant showed higher HR, lower LF, HF, and VLF powers, and a steeper power-law slope (p < 0.005, -0.0001) in an early night exposure to the real magnetic field, but not in other circadian stages. There was no significant difference between circadian responses to real and sham exposure in any variable at any circadian stage.

Toward chronocardiologic and chronomic insights: dynamics of heart rate associated with head-up tilting.

As a step towards investigating the chronome (i.e. the inferential endpoints of chaos, trends and rhythms) of heart rate (HR) variability (HRV), we investigated whether the fractality or complexity of HRV is affected by a head-up tilting (HUT) test in the morning after an overnight fast. Spectral and non-linear analyses of HR were performed on data gathered during an 80 degrees passive HUT test in 15 men and 28 women 32.8 +/- 11.5 years of age. The non-linear endpoints included the scaling exponents alpha1 (<11 beats) and alpha2 (>11 beats), which indicate fractal properties, calculated with detrended fluctuation analysis, and the approximate entropy (ApEn), a measure of overall complexity. Passive HUT increased alpha1 (from 0.986 +/- 0.217 to 1.370 +/- 0.185; P = 0.0001), but did not alter alpha2 (from 0.925 +/- 0.110 to 0.958 +/- 0.130; P = 0.19). A slight but statistically significant decrease in ApEn was seen during HUT (from 1.114 +/- 0.131 to 1.013 +/- 0.197; P = 0.002). In the tilt-up position, there was a statistically significant negative correlation between alpha1 and ApEn (r = -0.490; P < 0.05). In both the supine and the tilt-up position, alpha1 was correlated weakly with HF (r = -0.343 and r = -0.322, respectively), and strongly with LF/HF (r = 0.557 and r = 0.795), respectively. There was also a negative correlation between ApEn and LF/HF (r = -0.406 and r = -0.357, respectively). alpha2 did not correlate with any spectral or non-linear measures of HRV. Short-term fractal properties and complexity of HR were lowered with orthostatic stress. Alterations of the autonomic activities could be partly responsible for these changes and await extension of such studies to assess the broad spectral element of HRV, that includes, with components of approximately 3.6 and approximately 10.5 s, cycles with very much lower frequencies, along the scales of hours and even years, that critically modulate the mislabeled (only relatively high- and low-frequency) components in the range of seconds or minutes.