Elaine M. Hockman

Effects of nurse-managed telemonitoring on blood pressure at 12-month follow-up among Urban African Americans

Background: Nearly one in three adults in the United States has hypertension. Hypertension is one of the largest risk factors for cardiovascular diseases, and it is growing in prevalence, especially among African Americans. Objectives: To test the hypothesis that individuals who participate in usual care (UC) plus blood pressure (BP) telemonitoring (TM) will have a greater reduction in BP from baseline to 12-month follow-up than would individuals who receive UC only. Methods: A two-group, experimental, longitudinal design with block stratified randomization for antihypertensive medication use was used. African Americans with hypertension were recruited through free BP screenings offered in the community. Data were collected through a structured interview and brief physical exam. Cross tabs, repeated measures analysis of variance, and independent t tests were used to analyze the studys hypothesis. Results: The TM intervention group had a greater reduction in systolic BP (13.0 mm Hg) than the enhanced UC group (7.5 mm Hg; t = −2.09, p = .04) from baseline to the 12-month follow-up. Although the TM intervention group had a greater reduction in diastolic BP (6.3 mm Hg) compared with the enhanced UC group (4.1 mm Hg), the differences were not statistically significant (t = −1.56, p = .12). Discussion: Telemonitoring of BP resulted in clinically and statistically significant reductions in systolic BP over a 12-month period; if maintained over a longer period of time, the reductions could improve care and outcomes significantly for African Americans with hypertension.

Prevalence of HIV infection and HIV risk behaviors associated with living place: on-the-street homeless drug users as a special target population for public health intervention.

The study described here examined the prevalence of HIV infection as a function of place of residence and high-risk behaviors in six subpopulations of out-of-treatment drug injectors and crack cocaine users who participated in the National Institute on Drug Abuse (NIDA) Cooperative Agreement project. The subpopulations were blacks, Hispanics, and non-Hispanic whites sampled separately by gender. The research asked three questions: (a) Is the HIV infection rate higher among the on-the-street homeless than among those in other places of residence? (b) Do high-risk drug-related behaviors differ by housing status? and (c) What are the joint effects of high-risk drug-related behaviors and housing status on the probability of HIV infection? Overall, on-the-street homeless had a significantly higher HIV+ rate (19.0%) than the study population as a whole (11.2%). Rates differed by gender and race, with exceptionally high HIV+ rates for on-the-street homeless Hispanic males (29%) and females (32%) and for on-the-street homeless black females (38%). Having used drug works previously used by a HIV-infected person was a strong predictor of HIV+ status, as was frequency of drug injections and crack use. Having multiple sex partners was also a significant risk behavior. Findings argue against considering on-the-street homelessness as equivalent to shelter dwelling or aggregated homelessness for purposes of the AIDS epidemic. On-the-street homeless drug users were at strong risk for acquisition and transmission of HIV infection and therefore in need of targeted-racially relevant, ethnically relevant, and gender-relevant-public health interventions to help prevent the spread of AIDS.

Body Composition in Neonates: Relationship Between Measured and Derived Anthropometry with Dual-Energy X-Ray Absorptiometry Measurements

This study examined the relationship between measured and derived anthropometric measurements with dual-energy x-ray absorptiometry measured lean and fat mass at 3.0 ± 2.8 (SD) days in 120 neonates with birth weights appropriate (AGA; n = 74), large (LGA; n = 30); or small (SGA, n = 16) for gestational age. Anthropometric measurements, including total body weight and length, and regional measurements, including circumferences of head, chest, abdomen, midarm, and midthigh and dynamic skinfold thickness (15 and 60 s) at tricep, subscapular, suprailiac, and midthigh, were performed. Derived anthropometry included muscle and fat areas, and ratios were calculated from direct measurements. The skinfold thickness measurements between 15 and 60 s were highly correlated (r = 0.973–0.996, p < 0.001 for all comparisons). Strong correlations existed within the four circumferences of trunk and extremities, the four skinfolds, and the ratios of weight to length and its higher powers. Weight and length accounted for >97% of the variance of lean mass in AGA and SGA infants and 46% of the variance in LGA infants and for 80, 82, and 84% of the variance of fat mass in SGA, AGA, and LGA infants, respectively, whereas midarm:head circumference ratio and arm muscle and fat areas are the most important derived anthropometry in the prediction for body composition. They independently accounted for up to 16.5 and 10.2%, respectively, of the variance in body composition depending on the state of in utero growth. Thus, total body weight and length and some selected regional and derived anthropometry accounted for the vast majority of the variance of body composition.

Body composition of neonates from fan beam dual energy X-ray absorptiometry measurement.

BACKGROUND Fan beam dual energy x-ray absorptiometry (FB DXA) has recently been validated for the measurement of body composition in small subjects. This study represents the first report of body composition (bone mineral content, fat mass, and lean mass) in human neonates measured by FB DXA. METHODS FB DXA measurements were performed in 73 healthy singleton neonates with mean +/- SD birth weights 3354 +/- 316 g (range, 2720 to 3982 g) and gestational ages 39.5 +/- 1.2 weeks (range, 37 to 42 weeks). There were 26 white (11 male infants, 15 female infants), 42 African American (17 male infants, 25 female infants), and 5 Hispanic (4 male infants, 1 female infant) infants. The predictive ability of physiologic parameters to predict body composition measurements was determined with regression analysis. RESULTS The mean +/- SD for bone mineral content was 89.3 +/- 14.1 g, fat mass was 485 +/- 14.1 g, and lean mass was 2898 +/- 281.5 g. Weight was significantly correlated with all DXA measurements and was the single best predictor of body composition. Weight alone contributed 32% to 98% of the variance of the DXA measured parameters. Gender, race, and length were additional predictors that could be forced into a predictive equation for selected DXA dependent variables according to statistical significance. An independent gender effect was also demonstrated, with male infants having higher lean mass but lower fat mass. CONCLUSIONS Our data in human neonates demonstrated the ability of FB DXA to measure body composition. Body weight is the best physiologic predictor of overall body composition. There is also an independent gender effect on soft tissue body composition.

Palm olein in the fat blend of infant formulas: effect on the intestinal absorption of calcium and fat, and bone mineralization.

Objective: To evaluate the published clinical data on the physiologic effects of using palm oil and its low melting fraction, palm olein (PO) as a dominant lipid source in the fat blend in infant formulas. Design: A systematic search of Medline and the Cochrane Database of Systematic Reviews was performed to retrieve studies comparing infants who received infant formulas containing PO with those who received infant formulas without PO or which contained synthetic triacylglyceride as a source of palmitic acid. Outcomes of interest include intestinal fractional absorption of fat, palmitic acid and calcium; and bone mass. The effect size for each dependent variable in each published study was obtained by standardizing based on the difference in means between non-PO and PO group with respect to the standard deviation of the PO group. Trend analysis of the outcome of interest was performed when 3 or more between group comparisons were available. The comparison of effect size across different studies was based on all available data and includes results that showed no significant difference between infants fed PO or non-PO study formulas in the outcomes of interest. Results: Nine publications were identified with non-PO and PO comparison groups. The gestational ages of infants in the published studies were between 28 to 42 weeks and postnatal ages were birth to 192 days at study onset. Within each published study, there was some variability in the effect size between non-PO and PO groups. The standardized results were consistently significantly (p < 0.05) positive in favor of the feeding with non-PO formulas with respect to increased intestinal fractional absorption of fat, palmitic acid and calcium. The latter two variables were significantly different by at least 0.6 SD. Bone mass measured as total body bone mineral content was significantly higher in the non-PO group by at least 0.3 SD. Conclusion: The use of PO in infant formulas to match the human milk content of palmitic acid has unintended physiological consequences including diminished intestinal absorption of fat, palmitic acid and calcium and lower bone mass. The avoidance of PO or its substitution with synthetic triacylglyceride in infant formulas can prevent this detrimental effect.

Dual energy X-ray absorptiometry measurements in small subjects: conditions affecting clinical measurements.

Objective: To document the clinical and experimental situations that may affect DXA measurements in small subjects. Methods: 49 piglets (886g to 21100g) had measurements with either of two pencil beam densitometers (QDR 1000W and QDR 2000 Plus, Hologic Inc, Waltham, MA) using commercial infant (IWB) and adult whole body (AWB) software v5.71p and v5.71 respectively. AWB scans were analyzed with three additional software versions. 35 infants (2115 to 11564g) had IWB measurements. Results: DXA measurements of total weight, bone mineral content, bone area, bone mineral density, fat and lean mass from IWB scans (all piglets) and from AWB scans (piglets >12 kg) were highly reproducible (p < 0.001). A statistically significant change occurred in at least one of the DXA measurements from the use of different platforms, variations in the amount and placement of covering (e.g., blanket), placement of the external calibration standard, presence of radiographic contrast material, presence of movement artifact, delivery of an intravenous fluid bolus prior to scanning or improper delineation of external calibration standard during analysis. Additionally, results varied amongst different versions of software as well as between IWB and AWB softwares. Conclusion: In small subjects, consistency in the DXA techniques is paramount for valid and meaningful comparison of DXA data in bone mass and body composition.

Validation of Bone Mass and Body Composition Measurements in Small Subjects with Pencil Beam Dual Energy X-Ray Absorptiometry

Objective: To validate the most widely reported dual energy X-ray absorptiometry (DXA) technique for the measurement of bone mass and body composition in human infants with a piglet model. Methods: Duplicate scans were obtained in 13 piglets (1950g to 21100g) using a whole body densitometer (Hologic QDR 2000 plus, Hologic Inc., Waltham, MA) operated in the pencil-beam mode on a two platform (aluminum platform overlying a foam table pad) system. DXA measurements that included total weight, bone mineral content, fat and lean mass were compared with carcass weight and chemical analysis for ash and calcium content, fat and lean mass. Results: Measurements from duplicate DXA scans were nearly perfectly correlated (r = 0.98 to 1.00). DXA measurements were strongly predictive of scale weight and chemical composition for all piglets (adjusted r2 = 0.93 to 1.00, intraclass reliability coefficients = 0.943 to 0.999, p < 0.001 for all comparisons) although DXA bone mineral content consistently underestimated carcass ash and calcium content. Measured values from heavier piglets were not significantly different from values predicted from the lighter piglets’ data. Slopes from regression based on lighter versus heavier piglets were not significantly different except for the bone mineral content with carcass ash or calcium content. Conclusion: Our study validated the use of pencil beam DXA and its ability to determine relative changes in bone mass and body composition measurements over a much greater range of body weight than previous reports although its use as a direct indicator of nutrient requirement may be limited.

Technical considerations for fan-beam dual-energy x-ray absorptiometry body composition measurements in pediatric studies

BACKGROUND A piglet model was used to determine the influence of frequently encountered situations in clinical studies of infants and young children on fan-beam dual-energy x-ray absorptiometry (DXA) measurements. METHODS DXA scans of piglets (640 g to 21,100 g) were acquired in the infant and adult mode and were analyzed with 1 infant, 1 pediatric, and 3 versions of adult software. RESULTS The effect of repositioning of the piglets from the center to the periphery of the scanning table on DXA measurements included an average difference of up to 0.5% for total weight, 5.0% for bone mineral content, 5.6% for bone mineral density, 1.3% for lean mass, and 21.9% for fat mass (< or = .05, all comparisons) although no significant changes occurred when the piglets were scanned in symmetrical positions on either edge of the scanning table. Different posture (prone vs supine and side), varied number of blankets overlaid or wrapped around the piglet, and parenteral but not enteral bolus feeding could significantly alter fan-beam DXA measurements to varying extents. Adult and pediatric software underestimated bone area and bone mineral content but overestimated bone mineral density, lean mass, fat mass, and total weight compared with infant software measurements. However, strong predictive relationships among these fan-beam DXA data in subjects >10 kg allow systematic corrections of data from different scan modes and different software. CONCLUSIONS Attention to details and consistency in the technique for scan acquisition and analysis are critical to the generation of meaningful data and to allow for detection of true differences in DXA measurements of small subjects.

Fan beam dual energy X-ray absorptiometry body composition measurements in piglets.

Objectives: A piglet model was used to validate and cross validate the fan-beam (FB) dual energy X-ray absorptiometry (DXA) software vKH6 and to determine the predictive values of physiologic parameters (weight, length, age and gender) on body composition. Methods: Nineteen piglets (Group A: 600 to 21100 g) were used to validate the FB-DXA measurements of body composition based on chemical analysis of the carcass. An additional 22 piglets (Group B: 640 g to 17660 g) had FB-DXA measurements, and these values were compared to the predicted values generated from regression equations computed from group A piglets. Body composition for bone mass, lean mass and fat mass was based on ash weight, nitrogen and fat measured from three aliquots of homogenate from each carcass. Data from all piglets (n = 41) were used to determine the variations in body composition. Data analysis used regression, t test and analysis of variance. Results: Duplicate DXA (total weight TW, bone mineral content BMC, bone area BA, bone mineral density BMD, lean mass LM and fat mass FM) measurements were highly correlated (r = 0.98 to 1.00, p < 0.001 for all comparisons) and were not significantly different. No significant differences were found in the residuals from predicted versus measured DXA values between the larger and the smaller (<1.6 kg) piglets from Group A. For Group B piglets, the DXA measured TW of 5666 ± 5692 g (mean ± SD), LM (5063 ± 5048 g), FM (465 ± 510 g), BMC (138 ± 139 g), BA (486 ± 365 cm2) and BMD (0.235 ± 0.071 g/cm2) were highly significantly correlated with (r = 0.94 to 1.00, p < 0.001 for all comparisons) and were not significantly different from the predicted values. Data from all piglets (n = 41) showed that weight is the dominant predictor of whole body and regional body composition. Length, age or gender contributed to <2% of the variability of body composition. Conclusion: Body composition measurements using the FB DXA software vKH6 is highly reproducible. The software vKH6 is validated for use in a wide range of body weights and body composition, and cross-validated using a separate group of animals. Body weight is the dominant predictor of body composition in immature piglets.

Physiologic predictors of lumbar spine bone mass in neonates

Dual energy x-ray absorptiometry (DXA) of the lumbar spine (LS) was measured in 201 singleton infants with birth weights from 1152 to 3970 g and gestational ages from 27 to 42 wk. All infants were well and studied at a mean (±SD) of 2.1 (±1.6) days after birth. There were 75 Caucasian (46 males, 29 females) and 126 African American infants (58 males, 68 females). Scan acquisition of the first to fourth lumbar vertebrae was performed with a single beam whole body scanner (Hologic QDR 1000/W densitometer, Hologic Inc, Waltham, MA, U.S.A.) using the infant spine mode. Scan analysis was performed with software version 4.57Q and consistent region of interest. The SD of difference for duplicate LS scans is <1.4% at a mean bone mineral content (BMC) of 2.14 g. Results show that LS BMC, area, bone mineral density (BMD) increased by approximately 550%, 280% and 180%, respectively, between 27 and 42 wk gestational age. Body mass accounted for about 70% and 55% of the variance in BMC and BMD respectively. In contrast, the infants length appears to be the best determinant of LS area and accounts for about 75% of the variance in LS area. Race, gender or season has little or no effect on LS bone mass. There was progressive increase in BMC and area from first to fourth lumbar vertebra but BMD was significantly higher only at the fourth lumbar vertebra. We conclude that DXA LS can be performed even in small preterm infants. Its excellent precision, low radiation exposure and rapid scan acquisition offers promise as a useful tool for widespread use in pediatrics. Our data may be used as a basis for further studies in physiologic and pathologic situations that may affect bone mineralization in infants.