Direct and surrogate measures of the white-coat effect: methodological aspects and clinical relevance

Low autonomic arousal as a risk factor for reoffending: A population-based study

Background

Low resting heart rate (RHR) and low systolic blood pressure (SBP) are associated with criminal behavior. However, knowledge is lacking about their predictive value for reoffending.

Aim

We aimed to examine associations of RHR and SBP with reoffending in a large population-based sample.

Methods

We conducted a cohort study of all convicted male conscripts born in Sweden 1958–1990 (N = 407,533). We obtained data by linking Swedish population-based registers. Predictor variables were RHR and SBP, measured at conscription which was mandatory until 2010 for men at age 18. The outcome variable was reoffending, defined as criminal convictions (any crime, violent crime and non-violent crime), obtained from the National Crime Register. We used survival analyses to test for associations of RHR and SBP with reoffending, adjusting for pertinent covariates such as socioeconomic status, height, weight and physical energy capacity.

Results

In fully adjusted Cox regression models, men with lower RHR (≤60 bpm) had higher risk of reoffending (any crime: HR = 1.17, 95% CI: 1.14, 1.19, violent crime: HR = 1.23, 95% CI: 1.17, 1.29, non-violent crime: HR = 1.16, 95% CI: 1.14, 1.19), compared to men with higher RHR (≥ 82 bpm). Men with lower SBP (≤80 mmHg) had higher risk of reoffending (any crime: HR = 1.19, 95% CI: 1.17, 1.21, violent crime: HR = 1.16, 95% CI: 1.12, 1.20, non-violent crime: HR = 1.20, 95% CI: 1.18, 1.22), compared to men with higher SBP (≥138 mmHg).

Conclusions

Low autonomic arousal is associated with increased risk of reoffending. RHR and SBP should be investigated further as potential predictors for reoffending as they each may have predictive value in risk assessment protocols.

Altered profile of baroreflex and autonomic responses to lower body negative pressure in chronic orthostatic intolerance

BACKGROUND

Chronic orthostatic intolerance (COI) is a common and disabling autonomic syndrome of unclear pathophysiology. We tested the hypothesis that baroreflex and autonomic responses to graded lower body suction (LBNP, up to -40 mmHg) could be altered in COI patients.

METHODS

Electrocardiogram (ECG), non-invasive arterial blood pressure and respiratory activity were measured during progressive LBNP (seven patients and seven volunteers). Lumped arterial baroreflex sensitivity (alpha index), and its arterial and cardiopulmonary components, were assessed by multivariate closed-loop analysis of RR interval and systolic arterial pressure (SAP) spontaneous variabilities and respiration. Monovariate spectral analysis of RR interval and SAP variability provided markers of autonomic regulation of the sinoatrial (SA) node and of vascular sympathetic modulation.

RESULTS

Similar reductions in overall and cardiopulmonary baroreflex gain were observed in both groups in response to graded LBNP. In contrast, only controls demonstrated a selective increase in arterial baroreflex sensitivity, at low-grade LBNP. Clear increases in the low-frequency component of RR interval variability (LFRR) [and decreases in the high-frequency component of RR interval variability (HFRR), both in normalized units] were observed in controls with graded LBNP, while insignificant changes occurred in COI patients, who showed, conversely, exaggerated sympathetic vasomotor responses [as assessed by the low frequency component of SAP variability (LFSAP)].

CONCLUSIONS

Patients with chronic orthostatic intolerance show distinct signs of altered baroreflex and autonomic regulation of the SA node and of the vasculature in response to graded LBNP.

White coat hypertension: understanding the concept and examining the significance

Because the concept of white coat hypertension is evolving, a variety of definitions appear in the literature. There has also been continuing debate as to whether white coat hypertension is a benign clinical condition or is associated with increased hypertensive complications. This paper summarizes and evaluates the literature on white coat effect/hypertension, with a focus on the following aspects of the concepts: (1) alternative definitions, (2) prevalence and predictors, (3) prognostic significance, and (4) implications for clinical practice. The evidence suggests that white coat hypertension is not a harmless phenomenon. It is frequently associated with increased target-organ damage and often coexists with other cardiovascular risk factors. The extent of the presence of other risk factors may determine the risks associated with white coat hypertension. It is important for clinicians to understand the concept, learn to diagnose it properly, and develop strategies for evaluating risk levels so that patients receive the proper treatment.

[Blood pressure differences between consecutive days of ambulatory monitoring in hypertensive patients: the ABPM effect]

BACKGROUND

Ambulatory blood pressure monitoring is a method of blood pressure assessment that compensates for some of the limitations of office values. While a white-coat pressor effect on conventional determination has been defined and frequently used for the improved evaluation of hypertensive patients, there is no evidence that the ambulatory technique could also influence blood pressure.

PATIENTS AND METHOD

Aimed at testing and quantifying the extent and duration over time of a possible pressor effect due to ambulatory monitoring, we studied 387 mild-to-moderate hypertensive patients (160 men), aged 54.2 (14.3) (mean [SD]). Blood pressure and heart rate were measured at 20-min intervals during the day and at 30-min intervals at night for 48 consecutive hours, and physical activity was simultaneously evaluated at 1-min intervals by means of a wrist actigraph. One third of patients were evaluated twice or more times.

RESULTS

In hypertensive patients who were evaluated for the first time, results indicate a highly significant (p < 0.001) reduction, in the second day of monitoring as compared to the first, in the diurnal mean of systolic and diastolic blood pressure, but not in heart rate or physical activity. This pressor effect remains significant for at least the first 5 hours of monitoring. The nocturnal mean of blood pressure was, however, similar in the two days of sampling. This ambulatory monitoring effect could not be observed when patients were evaluated following the same sampling scheme at the second or further times.

CONCLUSIONS

Ambulatory monitoring for 48 consecutive hours reveals a statistically significant pressor response that could reflect a novelty effect in the use of the monitoring device for the first time. This effect has notable implications in both research and clinical daily practice, both for proper diagnosis of hypertension and evaluation of treatment efficacy.

Modeling the circadian variability of ambulatorily monitored blood pressure by multiple-component analysis

The use of a set of new end points derived from ambulatory blood pressure monitoring (ABPM), in addition to the blood pressure (BP) values themselves, has been advocated to improve the sensitivity and specificity in diagnosing hypertension and to evaluate a person's response to treatment. An adequate estimation of rhythmic parameters depends, however, on the ability to describe properly the circadian pattern of BP variability. The purpose of this study was to identify a simple model that could characterize sufficiently well the circadian pattern of BP in normotensive healthy volunteers sampled by ambulatory monitoring. We studied 278 clinically healthy Spanish adults (184 men), 22.7 +/- 3.3 yr of age, without medical history of hypertension and mean BP from ambulatory profiles always below 135/85 mmHg for systolic/diastolic BP, who underwent sequential ABPM providing a total of 1115 series of BPs and heart rates (HRs), sampled on each occasion at 0.5h intervals for 48 h. Subjects were assessed while adhering to their usual diurnal activity and nocturnal sleep routine, without restrictions but avoiding the use of medication. The circadian rhythm in BP and HR for each subject was established by multiple-component analysis. A statistically significant 24h component is documented for 97% of the BP profiles, with a significant second (12h) harmonic documented in 65% of the profiles. Other ultradian harmonic components were significant in less than 20% of the profiles. A statistically significant increase in the coefficient of determination (percent of overall variability explained by the function fitted to the data) was only obtained after including the periods of 24 and 12 h for BP, and periods of 24, 12, and 6 h for HR in the model components. Although other ultradian components can be demonstrated as statistically significant in a small percent of subjects, a rather simple model including only the two first harmonics of the 24h period describes sufficiently well, at the specified sampling rate, the circadian pattern of BP in normotensive subjects. Departure from this model could characterize overt pathology, as recently demonstrated in the diagnosis of preeclampsia.