Community characteristics modify the relationship between obesity prevention efforts and dietary intake in children: the Healthy Communities Study.

BACKGROUND: The influence of community characteristics on the effectiveness of childhood obesity prevention efforts is not well understood. OBJECTIVE: Examine the interaction of community characteristics with the relationship between community programmes and policies (CPPs) and dietary intake. METHODS: An observational study of 5138 children in grades K-8 in 130 US communities was conducted in 2013-2015. Key informant interviews identified and characterized CPPs. CPP scores were generated for the number of target behaviours (CPP-Behav) and the number of behaviour change strategies (CPP-Strat) addressed by all CPPs and CPPs with nutrition goals over the prior 6 years in each community. Dietary intake was assessed by dietary screener and included intake of sugar from sugar-sweetened beverages; energy-dense foods; fruits and vegetables; whole grains; and fibre. Multivariate statistical models assessed the interactions between US region, urbanicity, community-level income, and community-level race/ethnicity and CPP scores in relation to dietary intake. RESULTS: CPP-Strat was positively associated with healthier dietary intakes in the Northeast and West, and in high Hispanic communities; the reverse was true in the South, and in high African-American and low-income communities. The CPP-Behav was positively associated with healthier dietary intakes in the South and rural areas, and the reverse was true in the West. CONCLUSION: The relationships between CPP index scores and dietary intake were most strongly influenced by region and urbanicity and to a lesser extent by community-level race/ethnicity and income. Findings suggest that different considerations may be needed for childhood obesity prevention efforts in communities with different characteristics.

Associations of community programs and policies with children's dietary intakes: the Healthy Communities Study.

BACKGROUND: The impact of community-based obesity prevention efforts on child nutrition has not been adequately studied. OBJECTIVE: Examine relationships between number, type and intensity of community programs and policies (CPPs) and child nutrition. METHODS: An observational study of 5138 children (grades K-8) in 130 U.S. communities was conducted in 2013-2015. CPPs were identified by 10-14 key informant interviews per community. CPPs were characterized based on: count, intensity, number of different strategies used and number of different behaviours targeted. Scores for the prior 6 years were calculated separately for CPPs that addressed primarily nutrition, primarily physical activity (PA) or total combined. Child intakes were calculated from a dietary screener and dietary behaviours were based on survey responses. Multi-level statistical models assessed associations between CPP indices and nutrition measures, adjusting for child and community-level covariates. RESULTS: Implementing more types of strategies across all CPPs was related to lower intakes of total added sugar (when CPPs addressed primarily PA), sugar-sweetened beverages (for nutrition and PA CPPs) and energy-dense foods of minimal nutritional value (for total CPPs). Addressing more behaviours was related to higher intakes of fruit and vegetables (for nutrition and total CPPs) and fibre (total CPPs). Higher count and intensity (PA and total CPPs) were related to more consumption of lower fat compared with higher fat milk. A higher count (PA CPPs) was related to fewer energy-dense foods and whole grains. No other relationships were significant at P < 0.05. CONCLUSION: Multiple characteristics of CPPs to prevent obesity appear important to improve children's diets.

Objectives of community policies and programs associated with more healthful dietary intakes among children: findings from the Healthy Communities Study.

BACKGROUND: Rational planning of community policies and programs (CPPs) to prevent obesity requires an understanding of CPP objectives associated with dietary behaviours. OBJECTIVE: The objective of the study is to identify objectives of CPPs associated with healthful dietary behaviours. METHODS: An observational study identified 4026 nutrition CPPs occurring in 130 communities in the prior 6 years. Dietary intakes of fruits and vegetables, added sugar and sugar-sweetened beverages, among others, were reported among 5138 children 4-15 years of age from the communities, using a Dietary Screener Questionnaire with children age 9 years and older (parent assisted) or parent proxies for younger children. CPPs were documented through key informant interviews and characterized by their intensity, count, and objectives including target dietary behaviour and food environment change strategy. Associations between dietary intakes and CPP objectives were assessed using hierarchical statistical models. RESULTS: CPPs with the highest intensity scores that targeted fast food or fat intake or provided smaller portions were associated with greater fruit and vegetable intake (0.21, 0.19, 0.23 cup equivalents/day respectively with p values <0.01, 0.04, 0.03). CPPs with the highest intensity scores that restricted the availability of less healthful foods were associated with lower child intakes of total added sugar (-1.08 tsp/day, p < 0.01) and sugar from sugar-sweetened beverages (-1.63 tsp/day, p = 0.04). Similar associations were observed between CPP count and dietary outcomes. No other significant associations were found between CPP target behaviours or environmental strategies and dietary intakes/behaviours. CONCLUSION: CPPs that targeted decreases in intakes of less healthful foods and/or aimed to modify the availability of less healthful foods and portions were associated with healthier child dietary behaviours.

Associations between community programmes and policies and children's physical activity: the Healthy Communities Study.

BACKGROUND: Community initiatives to promote physical activity in children are common, but evidence supporting their effectiveness is limited. OBJECTIVES: The objective of this study is to examine the relationships between community programmes and policies and children's physical activity in a large and diverse sample of US communities. METHODS: Programmes and policies to promote children's physical activity were assessed in 130 communities by key informant interviews, and physical activity behaviours were measured by self-report and parental report in samples of children in each community (total n = 5138). Associations between composite indices of community programmes and policies and indicators of total and moderate-to-vigorous physical activity were examined without and with adjustment for demographic factors. RESULTS: An index reflecting the 6-year history of the number of behaviour change strategies used in community programmes and policies was positively associated with children's moderate-to-vigorous physical activity. This association was attenuated with adjustment for demographic factors. Effect modification analyses found that the association was positive among non-Hispanic children but was negative for Hispanic children. CONCLUSIONS: Community initiatives to promote physical activity in children were positively associated with children's physical activity in non-Hispanic children. Such initiatives were negatively associated with physical activity in Hispanic children, suggesting that future research should consider unique cultural factors when designing community initiatives to promote activity in this population sub-group.

Social support buffering of the relation between low income and elevated blood pressure in at-risk African-American adults.

Socioeconomic disadvantage has been linked to elevated blood pressure (BP), and the purpose of this study was to assess whether interpersonal social supports buffer these adverse relations in African-American adults. In three communities matched demographically, a subsample of participants (N = 204) of the Positive Action for Today's Health trial provided measures of perceived social support, annual household income, and BP. Multiple regression analyses with cross-product interactions were conducted using follow-up data. The sample had a mean age of 52.8 years (SD = 15.1), and was predominantly female (66 %) with a high body mass index (M = 33.5, SD = 14.7). Results indicated an inverse relation between social support and diastolic BP (B = -.178, p = .005), and also an interaction with income (p = .046), such that higher social support related to lower diastolic BP in the lowest-income individuals (B = -1.05). The same direct (B = -.141, p = .025) and interacting (B = -1.42, p = .040) social support effects were present for systolic BP, however the omnibus model for systolic BP was not significant, F(6, 196) = 1.80, p = .09. The hypothesized buffering effect of social support on the adverse relation of income to BP was partially supported in at-risk African-American adults. Future prevention efforts for reducing the impact of socioeconomic stress on BP may aim to increase perceptions of social support.

A computational study of the effect of windscreen shape and flow resistivity on turbulent wind noise reduction.

In this paper, numerical simulations are used to study the turbulent wind noise reduction effect of microphone windscreens with varying shapes and flow resistivities. Typical windscreen shapes consisting of circular, elliptical, and rectangular cylinders are investigated. A turbulent environment is generated by placing a solid circular cylinder upstream of the microphone. An immersed-boundary method with a fifth-order weighted essentially non-oscillatory scheme is implemented to enhance the simulation accuracy for high-Reynolds number flow around the solid cylinder as well as at the interface between the open air and the porous material comprising the windscreen. The Navier-Stokes equations for incompressible flow are solved in the open air. For the flow inside the porous material, a modified form of the Zwikker-Kosten equation is solved. The results show that, on average, the circular and horizontal ellipse windscreens have similar overall wind noise reduction performance, while the horizontal ellipse windscreen with medium flow resistivity provides the most effective wind noise reduction among all the considered cases. The vertical ellipse windscreen with high flow resistivity, in particular, increases the wind noise because of increased self-generation of turbulence.

How many days of pedometer monitoring predict weekly physical activity in adults?

BACKGROUND: The study purpose was to establish the number (and type) of days needed to estimate mean pedometer-determined steps/day in a field setting. METHODS: Seven days of data were collected from 90 participants (33 males, age = 49.1 +/- 16.2 years, BMI = 27.2 +/- 4.1 kg/m(2); 57 females, age = 44.8 +/- 16.9 years, BMI = 27.0 +/- 5.9 kg/m(2)). Mean steps/day were computed for all 7 days (the criterion), each single day, and combinations of days. Analyses included repeated measures ANOVA, intra-class correlations (ICC), and regression. RESULTS: There was a significant difference (P < 0.001) between days. The difference was limited to Sunday and accounted for 5% of the variance. ICC analyses indicated a minimum of 3 days is necessary to achieve a reliability of 0.80. The adjusted R(2) was 0.79 for a single day (specifically Wednesday), 0.89 for 2 days (Wednesday, Thursday), and 0.94 for 3 days (Wednesday, Thursday, Friday). Sunday was the last day to enter the model. CONCLUSIONS: Although there is a statistical difference between days, there is little practical difference, and the primary distinction appears limited to Sunday. Although a single day of collection is not acceptable, any 3 days can provide a sufficient estimate.

Performance bounds for passive sensor arrays operating in a turbulent medium: plane-wave analysis.

The performance bounds of a passive acoustic array operating in a turbulent medium with fluctuations described by a von Kármán spectrum are investigated. This treatment considers a single, monochromatic, plane-wave source at near-normal incidence. A line-of-sight propagation path is assumed. The primary interests are in calculating the Cramer-Rao lower bounds of the azimuthal and elevational angles of arrival and in observing how these bounds change with the introduction of additional unknowns, such as the propagation distance, turbulence parameters, and signal-to-noise ratio. In both two and three dimensions, it is found that for large values of the index-of-refraction variance, the Cramer-Rao lower bounds of the angles of arrival increase significantly at large values of the normalized propagation distance. For small values of the index-of-refraction variance and normalized propagation distance, the signal-to-noise ratio is found to be the limiting factor. In the two-dimensional treatment, it is found that the estimate of the angle of arrival will decouple from the estimates of the other parameters with the appropriate choice of array geometry. In three dimensions, again with an appropriate choice of array geometry, the estimates of the azimuth and elevation will decouple from the estimates of the other parameters, but due to the constraints of the model, will remain coupled to one another.

Atmospheric scattering for varying degrees of saturation and turbulent intermittency.

Atmospheric turbulence is inherently inhomogeneous and intermittent. Short periods of high activity are embedded in longer periods of relative calm. Local spatial and temporal changes in sound speed associated with this intermittency increase the likelihood of measuring large values of scattered acoustic signals. Previous work successfully predicted the probability density functions (pdf's) of fully saturated, scattered signals measured within an acoustic shadow zone [Wilson et al., J. Acoust. Soc. Am. 99, 3393-3400 (1996)]. The more general case of incompletely saturated scattering is considered in this paper; using the Rice-Nagakami distribution a theory is developed. The predicted intensity pdf has two free parameters: one to describe the degree of intermittency and a second for the degree of saturation. For validation purposes, outdoor propagation measurements were made over a flat, hard ground at ranges of 146-283 m and at frequencies of 50-540 Hz. The saturation parameter was determined from the acoustic data and also estimated from the turbulence conditions. The degree of saturation increased with frequency, and measured intensity pdf's were found to be in excellent agreement with the theory.

Sound propagation in a turbulent atmosphere near the ground: a parabolic equation approach.

The interference of the direct wave from the point source to the receiver and the wave reflected from the impedance ground in a turbulent atmosphere is studied. A parabolic equation approach for calculating the sound pressure p at the receiver is formulated. Then, the parabolic equation is solved by the Rytov method yielding expressions for the complex phases of direct and ground-reflected waves. Using these expressions, a formula for the mean squared sound pressure [absolute value(p)2] is derived for the case of anisotropic spectra of temperature and wind velocity fluctuations. This formula contains the "coherence factor," which characterizes the coherence between direct and ground-reflected waves. It is shown that the coherence factor is equal to the normalized coherence function of a spherical sound wave for line-of-sight propagation. For the case of isotropic turbulence, this result allows one to obtain analytical formulas for [absolute value(p)2] for the Kolmogorov, Gaussian, and von Karman spectra of temperature and wind velocity fluctuations. Using these formulas, the effects of temperature and wind velocity fluctuations, and the effects of different spectra of these fluctuations on the mean squared sound pressure, are numerically studied. Also the effect of turbulent anisotropy on the interference of direct and ground reflected waves is numerically studied. Finally, it is shown that the mean squared sound pressure [absolute value(p)2] calculated for the von Karman spectrum of temperature fluctuations agrees well with experimental data obtained in a laboratory experiment.

Statistical moments of the sound field propagating in a random, refractive medium near an impedance boundary.

Propagation of a monochromatic sound field in a refractive and turbulent medium near an impedance boundary is considered. Starting from the parabolic equation for a moving medium and using the Markov approximation, a closed equation for the statistical moments of arbitrary order of the sound-pressure field is derived. Numerical methods for directly solving the first- and second-moment versions of this equation are formulated. The first-moment formulation is very similar to parabolic equations (PEs) that are now widely used to calculate sound fields for particular realizations of a random medium. The second-moment formulation involves a large, fringed tridiagonal matrix, which is solved using iterative refinement and Cholesky factorization. The solution is computationally intensive and currently restricted to low frequencies. As an example, the first and second moments are directly calculated for upwind and downwind propagation of a sound wave through a turbulent atmosphere. For these cases, predictions from the second-moment PE were statistically indistinguishable from the result of 40 random trials calculated with a standard Crank-Nicholson PE, although the second-moment PE yielded smoother results due to its ensemble-average nature.

The role of gender and family support on dietary compliance in an African American adolescent hypertension prevention study.

Social support experiences vary markedly across gender groups, and little is known about the role of social support in promoting healthy dietary compliance in African American adolescents who are at increased risk for developing hypertension. This study examined the relation between gender, dietary social support, and compliance to a low sodium diet. Casual blood pressures were also examined in relation to dietary compliance and gender One hundred eighty-four healthy African American adolescents (83 boys, 101 girls) participated in an intensive 5-day low sodium diet (50 mEq/24 hr) as part of a hypertension prevention program. Emotional dietary social support from family members and friends was measured at baseline. Compliance was defined as urinary sodium excretion of < or = 50 mEq/24 hr at postsodium restriction. The results indicated a significant Gender x Compliance effect for positive family support (p < .05). Girls who were compliant reported higher levels of dietary support from family members (19.2 +/- 7.8) than boys who were compliant (16.9 +/- 7.0). In contrast, boys who were compliant reported lower levels of dietary support from family members (16.9 +/- 7.0) than boys who were not compliant (20.2 +/- 7.5). Systolic blood pressure showed a trend toward decreasing in compliant participants (104.4 +/- 8.4 vs. 101.7 +/- 8.0, mm Hg, p < .06), but the effect diminished when Quetelet Index (kg/m2) was controlled for in the analyses (p < .12). These results suggest that higher levels of emotional dietary support from family members are associated with better adherence to short-term sodium restriction for African American girls as compared to boys. Further research is needed to determine the long-term impact of social support on sodium restriction in adolescent populations.

The crystal structure of the GCY1 protein from S. cerevisiae suggests a divergent aldo-keto reductase catalytic mechanism.

The crystal structure of the GCY1 gene product from Saccharomyces cerevisiae has been determined to 2.5 A and is being refined. The model includes two protein molecules, one apo and one holo, per asymmetric unit. Examination of the model reveals that the active site surface is somewhat flat when compared with the other aldo-keto reductase structures, possibly accommodating larger substrates. The K(m) for NADPH (28.5 microM) is higher than that seen for other family members. This can be explained structurally by the lack of the 'safety belt' of residues seen in other aldo-keto reductases with higher affinity for NADPH. Catalysis also differs from the other aldo-keto reductases. The tyrosine that acts as an acid in the reduction reaction is flipped out of the catalytic pocket. This implies that the protein must either undergo a conformational change before catalysis can take place or that there is an alternate acid moiety.

Crystallization and aldo-keto reductase activity of Gcy1p from Saccharomyces cerevisiae.

Crystallization and preliminary X-ray diffraction studies of Gcy1p, an aldo-keto reductase from Saccharomyces cerevisiae, have been performed. Both the wild type and a double-mutant form of Gcy1p were crystallized using the hanging-drop method at 298 K; however, only the double-mutant form has so far yielded crystals suitable for X-ray diffraction analysis. These crystals belonged to the primitive monoclinic space group P2(1), with unit-cell parameters a = 50.94, b = 65.64, c = 86.23 A, beta = 92.64 degrees. Diffraction data were collected to 2.5 A. Assuming two 35 kDa subunits in the asymmetric unit yielded a V(m) of 2.06 A(3) Da(-1). Additionally, a kinetic study performed by measuring the rate of oxidation of NADPH in the presence of several substrates indicates that both wild-type and double-mutant proteins are enzymes possessing NADPH-dependent reductase activity.

Socioeconomic status and blood pressure reactivity in healthy black adolescents.

Adolescents in low-socioeconomic-status environments are more susceptible to illnesses, such as hypertension and cardiovascular diseases. This study examined the influence of both neighborhood- and family-level socioeconomic status (SES) on blood pressure (BP) reactivity in a healthy sample of 76 black adolescents. It was hypothesized that a higher level of parental education and/or income would reduce the elevated BP reactivity associated with living in poorer neighborhoods. Census-derived data were obtained using each participant's address. Neighborhood level of SES was based on percentage of households below the poverty line, female-headed households, owner-occupied housing, percentage vacant housing, and average number of persons per household. Family level of SES was based on self-reported level of parental education and annual family income. Adolescents participated in a competitive video game to establish their BP reactivity scores. As predicted, adolescents who lived in poorer neighborhoods had lower diastolic BPs if their parents were more (versus less) educated (P<0.05; 7+/-8 versus 13+/-6 mm Hg). Adolescents who lived in poorer neighborhoods also had significantly lower diastolic BP reactivity (P<0.05) if their family had a higher (versus lower) annual income (7+/-7 versus 12+/-8 mm Hg). These data are the first to demonstrate the buffering effect of family SES on the negative health consequences of living in low-SES neighborhoods in healthy black adolescents.

The prevalence of salt sensitivity in an African-American adolescent population.

This study examined the prevalence of salt-sensitivity (SS) in 140 healthy African-American adolescents. SS was defined as an increase in mean blood pressure > or =5 mm Hg from a 5-day low salt (Na+) diet (50 mmol/24 hr) to a 10-day high Na+ diet (150 mmol/24 hr NaCl supplement); remaining subjects were classified as salt-resistant (SR). Dietary compliance was defined as Na+ excretion < or =50 mmol/24 hr for the low Na+ diet and > or =165 mmol/24 hr for the high NaCl supplement diet. 31 (22%) subjects were classified as SS and 109 (78%) as SR. There were no significant differences between SS and SR subjects on baseline characteristics, family history of hypertension, or on resting blood pressure or heart rate measures. As expected, SS subjects showed a greater increase in mean, systolic, and diastolic blood pressures (P<.001 for all) than SR subjects in response to the high NaCl supplement. There was a greater increase in weight (P<.01) and Quetelet Index (P<.05) for SS than SR subjects in response to Na+ loading. These results are the first to show that SS is prevalent in a subgroup of healthy African-American adolescents.

Effects of potassium on blood pressure in salt-sensitive and salt-resistant black adolescents.

This study examined the effects of increasing dietary potassium on ambulatory blood pressure nondipping status (<10% decrease in blood pressure from awake to asleep) and cardiovascular reactivity in salt-sensitive and salt-resistant black adolescents. A sample of 58 normotensive (blood pressure, 101/57+/-9/4 mm Hg) black adolescents (aged 13 to 16 years) participated in a 5-day low sodium diet (50 mmol/24 h) followed by a 10-day high sodium diet (150 mmol/24 h NaCl supplement) to determine salt-sensitivity status. Participants showed a significant increase in urinary sodium excretion (24+/-19 to 224+/-65 mmol/24 h) and were identified as salt-sensitive if their mean blood pressure increase was >/=5 mm Hg from the low to high sodium diet. Sixteen salt-sensitive and 42 salt-resistant subjects were then randomly assigned to either a 3-week high potassium diet (80 mmol/24 h) or usual diet control group. Urinary potassium excretion significantly increased in the treatment group (35+/-7 to 57+/-21 mmol/24 h). At baseline, a significantly greater percentage of salt-sensitive (44%) compared with salt-resistant (7%) subjects were nondippers on the basis of diastolic blood pressure classifications (P<0.04). After the dietary intervention, all of the salt-sensitive subjects in the high potassium group achieved dipper status as a result of a drop in nocturnal diastolic blood pressure (daytime, 69 versus 67 mm Hg; nighttime, 69 versus 57 mm Hg). No significant group differences in cardiovascular reactivity were observed. These results suggest that a positive relationship between dietary potassium intake and blood pressure modulation can still exist even when daytime blood pressure is unchanged by a high potassium diet.

Ambulatory blood pressure nondipping status in salt-sensitive and salt-resistant black adolescents.

This study examined the relationship between salt sensitivity and ambulatory blood pressure in 53 healthy black adolescents. Salt sensitivity was defined as an increase in mean blood pressure greater than or exceeding 5 mm Hg from a 5-day low-salt diet (50 mmol/24 h) to a 10-day high-salt diet (150 mmol/24 h NaCl supplement). Sixteen subjects were salt sensitive and 37 subjects were salt resistant (showed < 5 mm Hg increase in mean blood pressure). Subjects were classified as dippers (> or =10% decrease in blood pressure from awake to asleep) based on their 24-h ambulatory blood pressure values. Nondippers showed higher systolic, diastolic, and mean asleep blood pressures than dippers (P < .05 for all). Salt-sensitive subjects showed greater daytime diastolic and mean blood pressures than salt-resistant subjects (P < .05 for both). A significantly greater percentage of nondippers were salt sensitive, compared with salt resistant for diastolic blood pressure (P < .001) and mean blood pressure (P < .05). For both of these blood pressure measures, 50% of the salt-sensitive subjects had a nondipping status, compared with only 5.4% of the salt-resistant subjects for diastolic blood pressure, and 18.9% of the salt-resistant subjects for mean blood pressure. These results are the first to indicate that salt sensitivity is associated with nondipper blood pressure status in a black normotensive adolescent population.

The influence of gender and emotional versus instrumental support on cardiovascular reactivity in African-American adolescents.

Research suggests that females seek out, prefer, and are more receptive to emotional support (encouragement), and that males seek out, prefer, and are more receptive to instrumental support (problem-solving). Thus, we hypothesized that boys would show lower blood pressure (BP) reactivity in response to instrumental than emotional or no support, and that girls would show lower BP reactivity in response to emotional than instrumental or no support. Forty-eight healthy African-American adolescents (50% males) participated in a role play conflict task and were randomized to receive either emotional, instrumental, or no support (presence only) from a confederate. Boys showed lower systolic blood pressure (SBP) reactivity in the instrumental than in the emotional or no support conditions and lower recovery SBP as compared to boys in the emotional or no support conditions. A similar pattern of results was demonstrated for diastolic blood pressure (DBP) reactivity. Girls, however, did not demonstrate lower BP reactivity in response to emotional as compared to instrumental support. These findings suggest that instrumental and emotional support differentially influence cardiovascular (CV) reactivity in African-American boys versus girls.