Novel Applications of Ultrasound Technology to Visualize and Characterize Myofascial Trigger Points and Surrounding Soft Tissue

Sikdar S, Shah JP, Gebreab T, Yen R-H, Gilliams E, Danoff J, Gerber LH. Novel applications of ultrasound technology to visualize and characterize myofascial trigger points and surrounding soft tissue.

Objective

To apply ultrasound (US) imaging techniques to better describe the characteristics of myofascial trigger points (MTrPs) and the immediately adjacent soft tissue.

Design

Four sites in each patient were labeled based on physical examination as active myofascial trigger points (A-MTrPs; spontaneously painful), latent myofascial trigger points (L-MTrPs; nonpainful), or normal myofascial tissue. US examination was performed on each subject by a team blinded to the physical findings. A 12∼5MHz US transducer was used. Vibration sonoelastography (VSE) was performed by color Doppler variance imaging while simultaneously inducing vibrations (∼92Hz) with a handheld massage vibrator. Each site was assigned a tissue imaging score as follows: 0, uniform echogenicity and stiffness; 1, focal hypoechoic region with stiff nodule; 2, multiple hypoechoic regions with stiff nodules. Blood flow in the neighborhood of MTrPs was assessed using Doppler imaging. Each site was assigned a blood flow waveform score as follows: 0, normal arterial flow in muscle; 1, elevated diastolic flow; 2, high-resistance flow waveform with retrograde diastolic flow.

Setting

Biomedical research center.

Participants

Subjects (N=9) meeting Travell and Simons' criteria for MTrPs in a taut band in the upper trapezius.

Interventions

Not applicable.

Main Outcome Measures

MTrPs were evaluated by (1) physical examination, (2) pressure algometry, and (3) three types of US imaging including gray-scale (2-dimensional [2D] US), VSE, and Doppler.

Results

MTrPs appeared as focal, hypoechoic regions on 2D US, indicating local changes in tissue echogenicity, and as focal regions of reduced vibration amplitude on VSE, indicating a localized, stiff nodule. MTrPs were elliptical, with a size of .16±.11cm². There were no significant differences in size between A-MTrPs and L-MTrPs. Sites containing MTrPs were more likely to have a higher tissue imaging score compared with normal myofascial tissue (P<.002). Small arteries (or enlarged arterioles) near A-MTrPs showed retrograde flow in diastole, indicating a highly resistive vascular bed. A-MTrP sites were more likely to have a higher blood flow score compared with L-MTrPs (P<.021).

Conclusions

Preliminary findings show that, under the conditions of this investigation, US imaging techniques can be used to distinguish myofascial tissue containing MTrPs from normal myofascial tissue (lacking trigger points). US enables visualization and some characterization of MTrPs and adjacent soft tissue.     

Exploring racial disparities in CHD mortality between blacks and whites across the United States: A geographically weighted regression approach

Coronary heart disease (CHD) mortality is one of the major contributors to racial disparities in health in the United States (US). We examined spatial heterogeneity in black-white differences in CHD mortality across the US and assessed the contributions of poverty and segregation. We used county-level, age-adjusted CHD mortality rates for blacks and whites in the continental US between 1996 and 2006. Geographically weighted regression was employed to assess spatial heterogeneity. There was significant spatial heterogeneity in black-white differences in CHD mortality (median black-white difference 17.7 per 100,000, 25th-75th percentile (IQR): 4.0, 34.0, P value for spatial non-stationarity <0.0001) before controlling for poverty and segregation. This heterogeneity was no longer present after accounting for county differences in race-specific poverty and segregation and interactions of these variables with race (median black-white difference -13.5 per 100,000, IQR: -41.3, 15.7,P value for spatial non-stationarity=0.4346). The results demonstrate the importance of spatial heterogeneity in understanding and eliminating racial disparities in CHD mortality. Additional research to identify the individual and contextual factors that explain the local variations in racial disparities is warranted.     

Geographic representation of the jackson heart study cohort to the African-American population in Jackson, Mississippi

Recent advances in geographic information systems software and multilevel methodology provide opportunities for more extensive characterization of "at-risk" populations in epidemiologic studies. The authors used age-restricted, geocoded data from the all-African-American Jackson Heart Study (JHS), 2000-2004, to demonstrate a novel use of the Lorenz curve and Gini coefficient to determine the representativeness of the JHS cohort to the African-American population in a geographic setting. The authors also used a spatial binomial model to assess the geographic variability in participant recruitment across the Jackson, Mississippi, Metropolitan Statistical Area. The overall Gini coefficient, an equality measure that ranges from 0 (perfect equality) to 1 (perfect inequality), was 0.37 (95% confidence interval (CI): 0.30, 0.45), indicating moderate representation. The population of sampled women (Gini coefficient = 0.34, 95% CI: 0.30, 0.39) tended to be more representative of the underlying population than did the population of sampled men (Gini coefficient = 0.49, 95% CI: 0.35, 0.61). Representative recruitment of JHS participants was observed in predominantly African-American and mixed-race census tracts and in the center of the study area, the area nearest the examination clinic. This is of critical importance as the authors continue to explore novel approaches to investigate the geographic variation in disease etiology.     

Toxicity of perfluoroalkyl substances (PFAS) toward embryonic stages of mahi-mahi (Coryphaena hippurus)

Perfluoroalkyl substances (PFAS) are highly persistent organic pollutants that have been detected in a wide array of environmental matrices and, in turn, diverse biota including humans and wildlife wherein they have been associated with a multitude of toxic, and otherwise adverse effects, including ecosystem impacts. In the present study, we developed a toxicity assay for embryonic stages of mahi-mahi (Coryphaena hippurus), as an environmentally relevant pelagic fish species, and applied this assay to the evaluation of the toxicity of “legacy” and “next-generation” PFAS including, respectively, perfluorooctanoic acid (PFOA) and several perfluoroethercarboxylic acids (PFECA). Acute embryotoxicity, in the form of lethality, was measured for all five PFAS toward mahi-mahi embryos with median lethal concentrations (LC₅₀) in the micromolar range. Consistent with studies in other similar model systems, and specifically the zebrafish, embryotoxicity in mahi-mahi generally (1) correlated with fluoroalkyl/fluoroether chain length and hydrophobicity, i.e., log P, of PFAS, and thus, aligned with a role of uptake in the relative toxicity; and (2) increased with continuous exposure, suggesting a possible role of development stage specifically including a contribution of hatching (and loss of protective chorion) and/or differentiation of target systems (e.g., liver). Compared to prior studies in the zebrafish embryo model, mahi-mahi was significantly more sensitive to PFAS which may be related to differences in either exposure conditions (e.g., salinity) and uptake, or possibly differential susceptibility of relevant targets, for the two species. Moreover, when considered in the context of the previously reported concentration of PFAS within upper sea surface layers, and co-localization of buoyant eggs (i.e., embryos) and other early development stages (i.e., larvae, juveniles) of pelagic fish species to the sea surface, the observed toxicity potentially aligns with environmentally relevant concentrations in these marine systems. Thus, impacts on ecosystems including, in particular, population recruitment are a possibility. The present study is the first to demonstrate embryotoxicity of PFAS in a pelagic marine fish species, and suggests that mahi-mahi represents a potentially informative, and moreover, environmentally relevant, ecotoxicological model for PFAS in marine systems.

     

How does Poisson kriging compare to the popular BYM model for mapping disease risks?

Background

Geostatistical techniques are now available to account for spatially varying population sizes and spatial patterns in the mapping of disease rates. At first glance, Poisson kriging represents an attractive alternative to increasingly popular Bayesian spatial models in that: 1) it is easier to implement and less CPU intensive, and 2) it accounts for the size and shape of geographical units, avoiding the limitations of conditional auto-regressive (CAR) models commonly used in Bayesian algorithms while allowing for the creation of isopleth risk maps. Both approaches, however, have never been compared in simulation studies, and there is a need to better understand their merits in terms of accuracy and precision of disease risk estimates.

Results

Besag, York and Mollie's (BYM) model and Poisson kriging (point and area-to-area implementations) were applied to age-adjusted lung and cervix cancer mortality rates recorded for white females in two contrasted county geographies: 1) state of Indiana that consists of 92 counties of fairly similar size and shape, and 2) four states in the Western US (Arizona, California, Nevada and Utah) forming a set of 118 counties that are vastly different geographical units. The spatial support (i.e. point versus area) has a much smaller impact on the results than the statistical methodology (i.e. geostatistical versus Bayesian models). Differences between methods are particularly pronounced in the Western US dataset: BYM model yields smoother risk surface and prediction variance that changes mainly as a function of the predicted risk, while the Poisson kriging variance increases in large sparsely populated counties. Simulation studies showed that the geostatistical approach yields smaller prediction errors, more precise and accurate probability intervals, and allows a better discrimination between counties with high and low mortality risks. The benefit of area-to-area Poisson kriging increases as the county geography becomes more heterogeneous and when data beyond the adjacent counties are used in the estimation. The trade-off cost for the easier implementation of point Poisson kriging is slightly larger kriging variances, which reduces the precision of the model of uncertainty.

Conclusion

Bayesian spatial models are increasingly used by public health officials to map mortality risk from observed rates, a preliminary step towards the identification of areas of excess. More attention should however be paid to the spatial and distributional assumptions underlying the popular BYM model. Poisson kriging offers more flexibility in modeling the spatial structure of the risk and generates less smoothing, reducing the likelihood of missing areas of high risk.     

Social Patterning of Cumulative Biological Risk by Education and Income Among African Americans

Objectives. We examined the social patterning of cumulative dysregulation of multiple systems, or allostatic load, among African Americans adults.Methods. We examined the cross-sectional associations of socioeconomic status (SES) with summary indices of allostatic load and neuroendocrine, metabolic, autonomic, and immune function components in 4048 Jackson Heart Study participants.Results. Lower education and income were associated with higher allostatic load scores in African American adults. Patterns were most consistent for the metabolic and immune dimensions, less consistent for the autonomic dimension, and absent for the neuroendocrine dimension among African American women. Associations of SES with the global allostatic load score and the metabolic and immune domains persisted after adjustment for behavioral factors and were stronger for income than for education. There was some evidence that the neuroendocrine dimension was inversely associated with SES after behavioral adjustment in men, but the immune and autonomic components did not show clear dose–response trends, and we observed no associations for the metabolic component.Conclusions. Findings support our hypothesis that allostatic load is socially patterned in African American women, but this pattern is less consistent in African American men.The adaptation of biological systems in response to stress and the maintenance of allostasis is a critical component in maintaining internal viability and functioning.1 Exposure to social and environmental stressors can result in physiologic dysregulation of multiple systems in the human body, often referred to as allostatic load.2,3 Allostatic load has been operationalized in epidemiological studies using combinations of biomarkers chosen to reflect the various physiological systems that may be affected by frequent and repeated exposure to stress.4,5 Measures of allostatic load have been linked to numerous disease-related processes,6 including cardiovascular4,7 and all-cause8 mortality.Because chronic stressors are often inversely associated with socioeconomic status (SES),9 it has been hypothesized that allostatic load may at least partly mediate the socioeconomic differences in cardiovascular disease and other health outcomes.10,11 To build evidence for this argument, numerous epidemiological studies have examined the socioeconomic patterning of allostatic load. In most studies, higher SES was associated with lower allostatic load,4,12–18 although at least 2 studies observed that this association was attenuated after adjustment for behavioral17 and psychosocial factors.18 The majority of US studies of SES and allostatic load, however, have focused predominantly on White samples.4,12–14 Relatively few studies have examined these associations in African American population samples and the extent to which these associations vary by gender or type of socioeconomic indicator used.12,13There are several reasons investigation of the SES patterning of allostatic load in African Americans is of interest. African Americans have been shown to have higher allostatic load scores19–21 and are more frequently exposed to chronic social and economic stressors9,22,23 than are Whites. This suggests that allostatic load could play a greater role in the SES patterning of cardiovascular and other health outcomes in African Americans than in Whites. If allostatic load truly reflects the dysregulation of biological systems because of repeated exposure to chronic stressors, a stronger SES–allostatic load gradient in African Americans would lend support for a more prominent role of psychosocial factors and stressors in the SES gradient in African American health.In investigating SES gradients in allostatic load in African Americans, variations by gender and SES measure used may be of special importance. Numerous studies have suggested that the SES gradient in cardiovascular risk factors (several of which are related to allostatic load measures) differs for men and women,24–29 although the underlying reasons for this remain to be determined. Although 2 studies have examined gender differences in the social patterning of allostatic load in African Americans,12,13 the results have been mixed and this patterning has not been extensively investigated in large African American samples. There is some evidence that the validity of various SES indicators may differ by race. For example, African Americans, compared with Whites, have been shown to have lower economic returns to education.30 Therefore, the socioeconomic patterning of allostatic load in African Americans could differ depending on the SES indicator used. Most prior research on the socioeconomic patterning of allostatic load has focused on educational attainment,6,12–16,18 with fewer studies considering income12–15 and occupation.17An important challenge in studying SES differences in allostatic load is identifying whether any observed associations reflect cumulative exposures to chronic stressors with consequences for multiple biological systems (as posited by the allostatic load theory) or whether the associations simply reflect socioeconomic patterning of behaviors. This is especially important given that many of the functional components of allostatic load (e.g., blood pressure and metabolic factors) are strongly influenced by behavioral factors (e.g., smoking and dietary intake). An added complexity is that behaviors may also partly mediate the effects of chronic stress on allostatic load. For these reasons, it is important for epidemiological studies to investigate associations of SES with allostatic load before and after controlling for behavioral factors.Using data from the Jackson Heart Study (JHS), we examined the extent to which education and income were cross-sectionally associated with a summary measure of allostatic load and allostatic load subcomponents in a large community-dwelling African American sample. We hypothesized that allostatic load would be inversely patterned by SES. According to prior evidence of stronger SES patterning of cardiovascular risk in women than in men27,28 and evidence of limited return to education in African Americans, 30 we hypothesized that the SES patterning would be stronger in women than in men and stronger for income than for education. We also examined to what extent the associations between allostatic load and SES persisted after adjustment for behavioral factors: cigarette smoking, physical activity, dietary intake, alcohol consumption, and sleep duration. The large and heterogeneous JHS population makes the JHS ideally suited for our investigation in terms of SES and the availability of detailed information on allostatic load biomarkers and behavioral factors.     

Race-specific associations between health-related quality of life and cellular aging among adults in the United States: evidence from the National Health and Nutrition Examination Survey

Purpose

Poor health-related quality of life (HRQOL) could lead to higher morbidity and mortality through telomere attrition or accelerated cellular aging. We conducted a cross-sectional analysis to examine the relationship between four dimensions of HRQOL and leukocyte telomere length (LTL) among a nationally representative sample of 3547 US adults (≥20 years) using the data from the 2001–2002 National Health and Nutrition Examination Survey.

Method

We used HRQOL survey information collected on individuals’ self-rated general health, recent physical health, recent mental health, and recent activity limitation. Telomere length was assessed using quantitative polymerase chain reaction. Multiple linear regressions were used to estimate the relationship between each dimension of HRQOL and log-transformed values of LTL with adjustment for sample weights and design effects.

Results

HRQOL-race interactions were significant, and the results were stratified by race. After controlling for demographic factors, disease conditions, and lifestyle variables, worse general health was significantly associated with shorter LTL for Blacks (coefficient, β: ?0.022, 95% Confidence Interval, 95% CI: ?0.03 to ?0.01), but not for Whites or Mexican Americans. Unwell physical health was associated with shorter telomere length for Whites (β: ?0.005, 95% CI: ?0.01 to ?0.001) only. Unwell mental health showed no significant association with LTL in any race.

Conclusions

Although longitudinal studies are needed to prove causality, our findings suggest that HRQOL could be associated with LTL shortening. We also found a possible racial difference in this association and recommend additional multiethnic studies to confirm this and to understand the reasons and consequences of this difference.