Longitudinal studies of blood pressure in children

A longitudinal study of six years was conducted to find out the pattern of longitudinal changes of blood pressure and to affirm the "tracking phenomenon" of blood pressure in children in China. We initially measured blood pressure and related parameters of 2,946 children (aged 4-14 years) in 1981 at Fanshan county, Beijing, and then two follow-up remeasurements were conducted in 1985 and 1987, respectively. The results indicated that: the average level of blood pressure increases with age even after adjusting for height and weight; tracking coefficients of systolic blood pressure range from weak to moderate levels, increasing with age. Only 30% of the children whose systolic blood pressure was beyond the 90th percentile of the systolic pressure distribution at the first examination remained at the same region after four years. Multiple stepwise regression was used to determine factors correlated with blood pressure. Our results indicate that systolic blood pressure in children is correlated with body weight, pulse rate, serum glucose and HDL-C, while diastolic blood pressure is correlated only with pulse rate and serum glucose.     

Psychological measures: practical issues in observational studies and clinical monitoring

Psychological measures are important because they can influence the expression of pain and physical function in patients with arthritis. A number of instruments are now available that measure psychological distress and how we as individuals manage stress. These instruments have undergone extensive validation, although more work is required to evaluate the performance of these instruments measuring change over time. One way to interpret psychological measures and to evaluate how they change over time is to use normative comparisons that are conditional on time and other relevant covariates, using statistical methods such as quantile regression. Such methods have been used to interpret the developmental, educational, and physical growth of children. We can use similar methods to interpret observational studies and to guide decisions within the context of clinical practice.     

Cardiovascular risks of hypertension: lessons from observational studies

Hypertension is an acknowledged major risk factor for cardiovascular disease and death in both men and women. Despite a historical focus by clinicians on the importance of diastolic blood pressure (DBP) risks, epidemiologic data from numerous large-scale studies have clearly demonstrated that both systolic blood pressure (SBP) and DBP are important determinants of cardiovascular risk. Recent analyses have described notable risks associated with isolated and borderline elevations of SBP, which predominate in the elderly, emphasizing the independent contribution of elevated SBP in determining overall risk. Overviews of large-scale treatment trials show that antihypertensive drug treatment confers a favorable net clinical benefit in patients with diastolic and isolated systolic hypertension, and the magnitude of risk reduction is comparable to that expected from the observational data. However, at any level of SBP or DBP, the absolute magnitude of risk varies widely depending on the burden of coexisting risk factors present. Therefore, it is essential that decisions regarding the urgency, risks and benefits of antihypertensive drug treatments be informed by accurate determinations of overall cardiovascular risk.     

Nutrient effects: discrepancy between data from controlled trials and observational studies

We describe the successful postoperative pain management in an 11-month-old infant who underwent bilateral thoracotomy, using continuous infusions of bupivacaine into two directly placed paravertebral catheters. Haemodynamic parameters and pain scores were measured 1-2 h for 60 h while the infusions were continued and, intermittently, blood samples were taken for subsequent measurement of serum bupivacaine concentrations. The technique provided effective pain relief and the infant required no other analgesia postoperatively. There were no adverse haemodynamic consequences or complications relating to either catheter placement or drug infusions. Serum concentrations of bupivacaine remained below toxic levels throughout the study period, though accumulation did occur.     

Analysis of behavioral durations in observational studies of social interaction.

Many social science disciplines investigate dyadic or triadic social interaction by recording the interactive behaviors as qualitative codes. This article introduces a method for analyzing and interpreting variation in the durations of coded behaviors obtained during such interactions. Using survival analysis and event history analysis as its basis, this article discusses the use of regression techniques that enable the researcher to assess how the distributions of behavioral durations depend on covariate observations. An analysis of conflicts between mothers and children illustrates the discussion, using the proportional hazards model. Behavioral and attitudinal differences among the mother–son dyad predicted variation in the durations of mothers' negative statements to their sons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preliminary core set of domains and reporting requirements for longitudinal observational studies in rheumatology

The minimized energy mapping of annexin V Trp-187 chi1 x chi2 isomerization supports the existence of two preferential rotameric orientations of the Trp side chain upon annexin V binding to membranes, in agreement with the time-resolved fluorescence results. They correspond to the perpendicular trans (-173 degrees, 73 degrees) and g- (-71 degrees, 83 degrees) rotamers and represent 59 and 28% of the population, respectively. The analysis of their local environment makes it possible to assign the trans rotamer to the long component and the g- rotamer to the short component of the biexponential fluorescence decay. The orientation of these rotamers relative to the protein core suggests a dual role for Trp-187, which might be involved both in the interaction with the phospholipid bilayer and in the formation of the annexin V 2-D array at the surface of the membrane.     

Interobserver agreement, reliability, and generalizability of data collected in observational studies.

Research in developmental and educational psychology has come to rely less on conventional psychometric tests and more on records of behavior made by human observers in natural and quasi-natural settings. Three coefficients that purport to reflect the quality of data collected in these observational studies are discussed: the interobserver agreement percentage, the reliability coefficient, and the generalizability coefficient. Three-facet generalizability studies that parallel intraobserver–interobserver, split-half, and test–retest reliability studies are described as examples. It is concluded that although high interobserver agreement is desirable in observational studies, high agreement alone is not sufficient to insure the quality of the data that are collected. Evidence of the reliability or generalizability of the data should also be reported. Other uses for generalizability theory (e.g., attribution of variance, single-S studies) are suggested, and further advantages of generalizability designs are discussed. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dietary magnesium intake and blood pressure: a qualitative overview of the observational studies

Published reports of 30 separate sets of analyses from 29 observational studies relating dietary intake of magnesium to blood pressure (BP) were identified through a comprehensive search using MEDLINE and BIDS-EMBASE. Three studies were prospective, 24 cross-sectional (25 reports), of which four also contained a longitudinal component, and two were obtained from baseline data in a trial. Various dietary methodologies were used: 24-h dietary recall (n = 12), food-frequency questionnaire (8), food record (7), and duplicate diet (2). Twelve reports compared magnesium intake or BP level between subgroups. Seven showed a negative association between magnesium intake and BP level, and five reported no association. From 18 of the 30 sets of analyses either a regression estimate or a Pearson correlation coefficient was reported. Many reports also allowed identification of subgroups by sex, age and race. Ninety population samples and subgroups could thus be identified from the 30 reports. All 11 Pearson-r correlation coefficients reported for systolic BP (SBP) (three significant, P < 0.05) and 10 (out of 12) Pearson-r correlation coefficients reported for diastolic BP (DBP) (four significant) were negative. Seven reports (13 subgroups for SBP, 11 subgroups for DBP) gave partial regression coefficients after adjustment; 10 (seven significant) and eight (six significant) were negative for SBP and DBP, respectively. For 13 subgroups in five papers, Pearson-r correlation coefficients were reported after adjustment for confounding factors. Eight (out of 13) showed a negative relationship for SBP and DBP. This review points to a negative association between dietary magnesium intake and BP. A systematic quantitative overview is needed to reconcile the inconsistencies of the results of individual studies and to quantify the size of such relationship.     

Longitudinal studies of psychological consequences of life changes in children and adults.

Conducted several longitudinal studies of children and adults to assess the validity of a hypothesized process of internal adaptation to external life changes. Data on the Thematic Apperception Test (TAT) were collected twice over 3 yrs from 284 students entering junior high or high school; 55 children in kindergarten through the 2nd grade, 113 students entering or graduating from college, 94 adults beginning marriage or becoming parents. It was hypothesized that changes would precipitate a receptive, dependent stance toward the external environment and that the postchange period would be characterized by gradual adoption of more assertive, or integrated, stances. Results support the hypotheses and indicate that additional changes in the posttransition period may interfere with adaptation to the initial change. Evidence that males and females may differ in their tolerance of the receptive and assertive stances is discussed. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential postmorbidity mortality in observational studies of risk factors for neurologic disorders

Selection bias may be introduced in case-control or cross-sectional studies, and the impact on the observed associations may be dramatic. Many authors have examined this issue primarily in the context of subject source (e.g. referral bias). The potential bias encountered when a risk factor associated with outcome is also associated with an increase in mortality among cases greater than that among those not developing the disease (e.g. selective survival) is examined here. The potential for selective survival bias arising in observational studies is demonstrated in studies of the etiology of neonatal seizures and Parkinson's disease.     

Use of observational data, including surveillance studies, for evaluating AIDS therapies

This article discusses some of the limitations of observational data for assessing therapeutic effects and categorizes observational studies according to the strength of evidence. Ecologic studies based on AIDS surveillance registries have demonstrated improvements over time in median survival following the onset of AIDS, especially for patients with an initial diagnosis of Pneumocystis carinii pneumonia. Some of this improvement may be the result of secular changes in the stage of disease at diagnosis or in the completeness of detection of deaths in these cohorts, however. Other ecologic studies of the use of AZT in various subgroups strongly suggest that treatment had a favorable impact on US AIDS incidence rates in gay men in the year beginning July 1987. This article is reprinted with minor changes from Chapter 24 of AIDS Clinical Trials.     

Longitudinal studies of food intake and weight of women from ages 18 to 56 years

Hepatitis B surface antigen was concentrated and purified from plasma by two simple steps of purification. In the first step the antigen was purified 24-fold by polyethylene glycol precipitation. An additional 10-fold purification was achieved by batchwise adsorption to hydroxylapatite and subsequent elution with 0.02 M sodium phosphate buffer.     

The importance of covariate selection in controlling for selection bias in observational studies.

The assumption of strongly ignorable treatment assignment is required for eliminating selection bias in observational studies. To meet this assumption, researchers often rely on a strategy of selecting covariates that they think will control for selection bias. Theory indicates that the most important covariates are those highly correlated with both the real selection process and the potential outcomes. However, when planning a study, it is rarely possible to identify such covariates with certainty. In this article, we report on an extensive reanalysis of a within-study comparison that contrasts a randomized experiment and a quasi-experiment. Various covariate sets were used to adjust for initial group differences in the quasi-experiment that was characterized by self-selection into treatment. The adjusted effect sizes were then compared with the experimental ones to identify which individual covariates, and which conceptually grouped sets of covariates, were responsible for the high degree of bias reduction achieved in the adjusted quasi-experiment. Such results provide strong clues about preferred strategies for identifying the covariates most likely to reduce bias when planning a study and when the true selection process is not known. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Longitudinal studies of neutralizing antibody responses to rotavirus in stools and sera of children following severe rotavirus gastroenteritis

Rotavirus-neutralizing antibody responses in sera and stools of children hospitalized with rotavirus gastroenteritis and then monitored longitudinally were optimally detected by using local rotavirus strains. Stool responses were highest on days 5 to 8 after the onset of diarrhea. Longitudinal monitoring suggested that serum neutralizing antibody responses were a more useful measure of severely symptomatic rotavirus infection than stool responses but that stool antibody responses may be a useful measure of rotavirus immunity.     

Extemporaneous prescribing module 3

Australian Family Physician is pleased to be able to present a home course in extemporaneous prescribing, an interesting area that is poorly understood by many practitioners, especially recent graduates. Dr Bernard Kelly has been teaching this discipline to Family Medicine Trainees in New South Wales for many years and has written a series of modules to be placed in the journal during 1993. A question is included at the end of each module.     

Longitudinal studies of immune function in cattle experimentally infected with bovine immunodeficiency-like virus and/or bovine leukemia virus

The effects of single or dual infection with bovine immunodeficiency-like virus (BIV) and/or, bovine leukemia virus (BLV) on bovine immune function were examined over a 4 year period. Holstein calves were infected with BIV (four calves), BLV (five calves), BIV and BLV (five calves), or sham inoculated (three calves). Lymphocyte blastogenesis to mitogens, seven tests of neutrophil function, and mononuclear cell subset analysis by flow cytometry (BoCD4, BoCD8, BoCD2, BoWC1, sIgM+, and monocytes) were performed at regular intervals to 49 months post-infection. These data were analyzed for main effects of each virus and interaction as a 2 x 2 factorial. BIV infected cattle had lower neutrophil antibody-dependent cell-mediated cytotoxicity and iodination responses during 2 of the 4 years post-infection (P < 0.05). BIV infection was not associated with any long-term significant changes in lymphocyte blastogenesis to mitogens or changes in mononuclear cell subset numbers in blood. There was a tendency for animals infected with BIV alone to have decreased lymphocyte blastogenic responses to mitogens, but this was not statistically significant. BLV infection caused an increase in total mononuclear cells with no dramatic shift in the relative proportions of the various subsets. Co-infection with BIV and BLV did not consistently cause a different response than either virus did individually. One BIV infected animal died of non-BLV lymphosarcoma 7 months after infection. All other animals had no unusual clinical signs. In summary, infection with BIV caused a significant, temporary decrease in neutrophil function with no consistent statistically significant alteration in lymphocyte blastogenesis or mononuclear cell numbers during the first 4 years after infection. BLV infection caused an increase in lymphocyte numbers, and there appeared to be no synergism between the viruses.     

Longitudinal studies in organizational stress research: a review of the literature with reference to methodological issues

Demonstrating causal relationships has been of particular importance in organizational stress research. Longitudinal studies are typically suggested to overcome problems of reversed causation and third variables (e.g., social desirability and negative affectivity). This article reviews the empirical longitudinal literature and discusses designs and statistical methods used in these studies. Forty-three longitudinal field reports on organizational stress were identified. Most of the investigations used a 2-wave panel design and a hierarchical multiple regression approach. Six studies with 3 and more waves were found. About 50% of the studies analyzed potential strain-stressor (reversed causation) relationships. In about 33% of the studies there was some evidence of reverse causation. The power of longitudinal studies to rule out third variable explanations was not realized in many studies. Procedures of how to analyze longitudinal data are suggested.     

Identification and observational learning from films.

In 2 studies of 25 class rooms of 7th grade children, it was noted that viewers "identify themselves with the like-sexed leading character, in viewing a movie which included both a strong male and strong female lead. With respect to similarity of social class, however, viewers were more likely to choose the protagonist whose social class corresponded with the viewer's aspired social class, rather than his current objective status." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motoric and symbolic mediation in observational learning.

The observers' motoric and symbolic representations of a model's behavior are important mediators in observational learning. The observers' spontaneous use of these mediators may be influenced by their familiarity with responses performed by a model and by their intention to learn these responses. Unfamiliar observers do not have symbolic codes available for the model's responses, so they may rely on motor mimicry. Familiar observers have symbolic codes available, so they may employ those codes and, possibly, motor mimicry as mediators. Spontaneous mediation may also depend on whether observers intend to learn these responses. Three experiments with 132 undergraduates revealed that familiar observers used motoric and symbolic mediators, whereas unfamiliar observers primarily used motor mimicry. Symbolic coding facilitated familiar but not unfamiliar observers' learning; unfamiliar observers' learning was related to motor mimicry. Intention to learn increased motor mimicry but not symbolic coding. An interpretation is offered for the observers' pervasive use of motor mimicry. (3 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)