ABSTRACT
This corrects the article DOI: 10.1038/jhh.2016.100.
ABSTRACT
Apparent treatment-resistant hypertension (aTRH) is associated with adverse cardiovascular outcomes. aTRH is common and disproportionately affects African Americans. The objective of this study is to explore psychosocial correlates of aTRH in a population-based cohort of African Americans with hypertension. The sample included 1392 participants in the Jackson Heart Study with treated hypertension who reported being adherent to their antihypertensive medications. aTRH was defined as uncontrolled clinic BP (⩾140/90 mm Hg) with ⩾3 classes of antihypertensive medication or treatment with ⩾4 classes of antihypertensive medication, including a diuretic. Self-reported medication adherence was defined as taking all prescribed antihypertensive medication in the 24 h before the study visit. The association of psychosocial factors (chronic stress, depressive symptoms, perceived social support and social network) with aTRH was evaluated using Poisson regression with progressive adjustment for demographic, clinical and behavioural factors. The prevalence of aTRH was 15.1% (n=210). Participants with aTRH had lower social network scores (that is, fewer sources of regular social contact) compared with participants without aTRH (P<0.01). No other psychosocial factors differed between groups. Social network was also the only psychosocial factor that was associated with aTRH prevalence in regression analyses. In age-, sex-adjusted and fully adjusted models, one additional unique source of social contact was associated with a 19% (PR=0.81; 95% confidence interval (CI): 0.68-0.94, P=0.001) and a 13% (PR=0.87; 95% CI 0.74-1.0, P=0.041) lower prevalence of aTRH, respectively. Social network was independently associated with aTRH and warrants further investigation as a potentially modifiable determinant of aTRH in African Americans.
Subject(s)
Antihypertensive Agents/therapeutic use , Hypertension/psychology , Black or African American/psychology , Cohort Studies , Cross-Sectional Studies , Female , Humans , Hypertension/drug therapy , Male , Middle Aged , Social Support , Treatment FailureABSTRACT
Non-Gaussian height fluctuations occurring on the fueling time scale of a slowly driven rice pile match those observed in some turbulent/critical phenomena, forming an anticorrelated random fractal process with Hurst exponent H=0.2. Inspired by this observation, the concept of fractional Brownian motion (FBM) is extended to treat stochastic processes with skewed increments. Simulations of this process for antipersistent motion have first return time distribution deviating from the t(-2+H) law for FBM. The first return time distribution of this fractional non-Brownian motion describes and quantitatively determines the trapping-time distribution of grains in rice piles upon incorporating a continuous representation of the additional height fluctuations that occur on the time scale between fueling events.
ABSTRACT
Diagnostics applied to a rice-pile cellular automaton reveal different mechanisms producing power-law behaviors of statistical attributes of grains which are germane to self organised critical phenomena. The probability distributions for these quantities can be derived from two distinct random walk models that account for correlated clustered behavior through incorporating fluctuations in the number of steps in the walk. The first model describes the distribution for a spatial quantity, the resultant flight length of grains. This has a power-law tail caused by grains moving through a discrete, power-law distributed number of random steps of finite length. Developing this model into a random walk obtains distributions for the resultant flight length with characteristics similar to Lévy distributions. The second random walk model is devised to explain a temporal quantity, the distribution of "trapping" or "residence" times of grains at single locations in the pile. Diagnostics reveal that the trapping time can be constructed as a sum of "subtrapping times," which are described by a Lévy distribution where the number of terms in the sum is a discrete random variable accurately described by a negative binomial distribution. The infinitely divisible, two-parameter, limit distribution for the resultant of such a random walk is discussed, and describes a dual-scale power-law behavior if the number fluctuations are strongly clustered. The form for the distribution of transit times of grains results as a corollary.
ABSTRACT
Random walks with step number fluctuations are examined in n dimensions for when step lengths comprising the walk are governed by stable distributions, or by random variables having power-law tails. When the number of steps taken in the walk is large and uncorrelated, the conditions of the Lévy-Gnedenko generalization of the central limit theorem obtain. When the number of steps is correlated, infinitely divisible limiting distributions result that can have Lévy-like behavior in their tails but can exhibit a different power law at small scales. For the special case of individual steps in the walk being Gaussian distributed, the infinitely divisible class of K distributions result. The convergence to limiting distributions is investigated and shown to be ultraslow. Random walks formed from a finite number of steps modify the behavior and naturally produce an inner scale. The single class of distributions derived have as special cases, K distributions, stable distributions, distributions with power-law tails, and those characteristic of high and low frequency cascades. The results are compared with cellular automata simulations that are claimed to be paradigmatic of self-organized critical systems.
