James B. Hittner

Relationships among Internet use, personality, and social support

Abstract Competing claims have been presented in the literature regarding the impact of Internet use on social support. Some theorists have suggested that Internet use increases social interaction and support (Silverman, 1999, American Psychologist 54, 780–781), while others have argued that it leads to decreased interaction and support (Kiesler & Kraut, 1999, American Psychologist 54, 783–784). This study was designed to address this issue by examining the relationships among Internet use, personality, and perceived social support. Two-hundred and six participants completed questionnaires that assessed Internet use, personality (agreeableness, conscientiousness, extraversion, neuroticism, openness), and perceived social support. Using principal components analysis, individual computer activities were combined into three primary factors: Technical, Information Exchange, and Leisure. Correlation and regression analyses revealed only a marginal relationship between computer use and social support. Similarly, only modest associations were found between personality and computer use. However, personality did moderate the relationship between computer use and social support. That is, on two occasions, high computer use coupled with high personality was associated with decreased perceived social support and on a third occasion this combination resulted in increased perceived social support. These results help to address some of the inconsistencies that have been reported in the literature.

Testing the significance of a correlation with nonnormal data: comparison of Pearson, Spearman, transformation, and resampling approaches.

It is well known that when data are nonnormally distributed, a test of the significance of Pearsons r may inflate Type I error rates and reduce power. Statistics textbooks and the simulation literature provide several alternatives to Pearsons correlation. However, the relative performance of these alternatives has been unclear. Two simulation studies were conducted to compare 12 methods, including Pearson, Spearmans rank-order, transformation, and resampling approaches. With most sample sizes (n ≥ 20), Type I and Type II error rates were minimized by transforming the data to a normal shape prior to assessing the Pearson correlation. Among transformation approaches, a general purpose rank-based inverse normal transformation (i.e., transformation to rankit scores) was most beneficial. However, when samples were both small (n ≤ 10) and extremely nonnormal, the permutation test often outperformed other alternatives, including various bootstrap tests.

A Monte Carlo Evaluation of Tests for Comparing Dependent Correlations

Abstract The authors conducted a Monte Carlo simulation of 8 statistical tests for comparing dependent zero-order correlations. In particular, they evaluated the Type I error rates and power of a number of test statistics for sample sizes (Ns) of 20, 50, 100, and 300 under 3 different population distributions (normal, uniform, and exponential). For the Type I error rate analyses, the authors evaluated 3 different magnitudes of the predictor-criterion correlations (py,x1 = py,x2=.1, .4, and .7). For the power analyses, they examined 3 different effect sizes or magnitudes of discrepancy between py,x2 and py,x2 (values of .1, .3, and .6). They conducted all of the simulations at 3 different levels of predictor intercorrelation (px1,x2 = .1, .3, and .6). The results indicated that both Type I error rate and power depend not only on sample size and population distribution, but also on (a) the predictor intercorrelation and (b) the effect size (for power) or the magnitude of the predictor-criterion correlations (for Type I error rate). When the authors considered Type I error rate and power simultaneously, the findings suggested that O. J. Dunn and V. A. Clarks (1969) z and E. J. Williamss (1959) t have the best overall statistical properties. The findings extend and refine previous simulation research and as such, should have greater utility for applied researchers.

Acquisition of Hemozoin by Monocytes Down-Regulates Interleukin-12 p40 (IL-12p40) Transcripts and Circulating IL-12p70 through an IL-10-Dependent Mechanism: In Vivo and In Vitro Findings in Severe Malarial Anemia

ABSTRACT Severe malarial anemia (SMA) is a primary cause of morbidity and mortality in immune-naïve infants and young children residing in areas of holoendemic Plasmodium falciparum transmission. Although the immunopathogenesis of SMA is largely undefined, we have previously shown that systemic interleukin-12 (IL-12) production is suppressed during childhood blood-stage malaria. Since IL-10 and tumor necrosis factor alpha (TNF-α) are known to decrease IL-12 synthesis in a number of infectious diseases, altered transcriptional regulation of these inflammatory mediators was investigated as a potential mechanism for IL-12 down-regulation. Ingestion of naturally acquired malarial pigment (hemozoin [PfHz]) by monocytes promoted the overproduction of IL-10 and TNF-α relative to the production of IL-12, which correlated with an enhanced severity of malarial anemia. Experiments with cultured peripheral blood mononuclear cells (PBMC) and CD14+ cells from malaria-naïve donors revealed that physiological concentrations of PfHz suppressed IL-12 and augmented IL-10 and TNF-α by altering the transcriptional kinetics of IL-12p40, IL-10, and TNF-α, respectively. IL-10 neutralizing antibodies, but not TNF-α antibodies, restored PfHz-induced suppression of IL-12. Blockade of IL-10 and the addition of recombinant IL-10 to cultured PBMC from children with SMA confirmed that IL-10 was responsible for malaria-induced suppression of IL-12. Taken together, these results demonstrate that PfHz-induced up-regulation of IL-10 is responsible for the suppression of IL-12 during malaria.

Bacteremia in Kenyan Children Presenting with Malaria

ABSTRACT Since the etiologies and clinical outcomes of bacteremia in children with Plasmodium falciparum infections, particularly in areas of holoendemic malaria transmission, are largely unexplored, blood cultures and comprehensive clinical, laboratory, hematological, and nutritional parameters for malaria-infected children (aged 1 to 36 months, n = 585 patients) were investigated at a rural hospital in western Kenya. After the exclusion of contaminant microorganisms, the prevalence of bacteremia was 11.7% in the cohort (n = 506), with nontyphoidal Salmonella spp. being the most common isolates (42.4%). Bacteremia was found to occur in a significantly higher proportion of females than males and was associated with elevated blood glucose concentrations and lowered malaria parasite and hemoglobin (Hb) levels compared to those in abacteremic participants. In addition, the incidences of respiratory distress and severe malarial anemia (SMA; Hb level of <6.0g/dl) were nonsignificantly greater in children with bacteremia. Mortality was 8.5-fold higher in children with bacteremia. Multivariate logistic regression analyses revealed that bacteremia was significantly associated with reduced incidences of high-density parasitemia (HDP; ≥10,000/μl) and increased incidences of malnutrition (i.e., underweight; weight-for-age Z score of <−2 using the NCHS system). Since previous studies showed that bacteremia caused by Gram-negative organisms is associated with enhanced anemia and mortality, multivariate logistic regression was also performed separately for randomly age- and gender-matched children with bacteremia caused by Gram-negative organisms (n = 37) and for children found to be abacteremic (n = 74). These results revealed that the presence of bacteremia caused by Gram-negative organisms was significantly associated with reduced HDP, enhanced susceptibility to respiratory distress, SMA (Hb level of <6.0 g/dl), and being underweight (Z score, <−2). Data presented here from a region of holoendemic P. falciparum transmission demonstrate that although bacteremia is associated with reduced malaria parasitemia, a number of unfavorable clinical outcomes, including malnutrition, respiratory distress, anemia, and mortality, are elevated in children with bacteremia, particularly in cases of Gram-negative origin.

Role of monocyte-acquired hemozoin in suppression of macrophage migration inhibitory factor in children with severe malarial anemia.

ABSTRACT Severe malarial anemia (SMA), caused by Plasmodium falciparum infections, is one of the leading causes of childhood mortality in sub-Saharan Africa. Although the molecular determinants of SMA are largely undefined, dysregulation in host-derived inflammatory mediators influences disease severity. Macrophage migration inhibitory factor (MIF) is an important regulator of innate inflammatory responses that has recently been shown to suppress erythropoiesis and promote pathogenesis of SMA in murine models. To examine the role of MIF in the development of childhood SMA, peripheral blood MIF production was examined in Kenyan children (aged <3 years, n = 357) with P. falciparum malarial anemia. All children in the study were free from bacteremia and human immunodeficiency virus type 1. Since deposition of malarial pigment (hemozoin [Hz]) contributes to suppression of erythropoiesis, the relationship between MIF concentrations and monocytic acquisition of Hz was also examined in vivo and in vitro. Circulating MIF concentrations declined with increasing severity of anemia and significantly correlated with peripheral blood leukocyte MIF transcripts. However, MIF concentrations in peripheral blood were not significantly associated with reticulocyte production. Multivariate regression analyses, controlling for age, gender, and parasitemia, further revealed that elevated levels of pigment-containing monocytes (PCM) was associated with SMA and decreased MIF production. In addition, PCM levels were a better predictor of hemoglobin and MIF concentrations than parasite density. Additional experiments in malaria-naive individuals demonstrated that hemozoin caused both increased and decreased MIF production in cultured peripheral blood mononuclear cells (PBMC) in a donor-specific manner, independent of apoptosis. However, PBMC MIF production in children with acute malaria progressively declined with increasing anemia severity. Results presented here demonstrate that acquisition of hemozoin by monocytes is associated with suppression of peripheral blood MIF production and enhanced severity of anemia in childhood malaria.

Social Support Coping Mediates the Relationship between Gender and Posttraumatic Growth

Females tend to report greater levels of posttraumatic growth following trauma than males. Little is known about why such an association exists. This study examined whether social support coping might mediate the relationship between gender and posttraumatic growth. College students and community residing adults ( N = 221) recalled a stressful or traumatic event that they had recently experienced and responded to measures of posttraumatic growth and coping while keeping this event in mind. Gender was significantly associated with both social support coping and growth while social support coping was a partial mediator of the relationship between gender and posttraumatic growth.

Factorial Invariance of the 13-item Sense of Coherence Scale across Gender

This study examined the gender invariance of the 13-item Sense of Coherence (SOC) scale. Confirmatory factor analyses indicated that a single factor model with one pair of correlated errors fit the data well. Invariance testing indicated that the scale is both congeneric and tau equivalent, meaning that a single latent SOC construct holds equally well for males and females, and that both genders demonstrate an equivalent pattern of factor loadings. There was little evidence in support of latent factor mean equivalence across gender. Explanations for the lack of factor mean equivalence were discussed and recommendations for future research were suggested.

A Psychosocial Resilience Model to Account for Medical Well-being in Relation to Sense of Coherence

We tested the suggestion that Sense of Coherence (SOC) may enhance medical well-being by virtue of a favorably balanced profile of psychosocial assets relative to liabilities. Results derived from a sample of 81 young adults who responded to a battery of inventories supported the Psychosocial Resilience Model. Our findings provide preliminary evidence to suggest that a favorable balance between psychosocial ‘protective’ and ‘risk’ factors may, in part, help explain why people with a strong SOC enjoy high levels of medical well-being.

Hematological predictors of increased severe anemia in Kenyan children coinfected with Plasmodium falciparum and HIV-1.

Malaria and HIV‐1 are coendemic in many developing countries, with anemia being the most common pediatric hematological manifestation of each disease. Anemia is also one of the primary causes of mortality in children monoinfected with either malaria or HIV‐1. Although our previous results showed HIV‐1(+) children with acute Plasmodium falciparum malaria [Pf(+)] have more profound anemia, potential causes of severe anemia in coinfected children remain unknown. As such, children with P. falciparum malaria (aged 3–36 months, n = 542) from a holoendemic malaria transmission area of western Kenya were stratified into three groups: HIV‐1 negative [HIV‐1(−)/Pf(+)]; HIV‐1 exposed [HIV‐1(exp)/Pf(+)]; and HIV‐1 infected [HIV‐1(+)/Pf(+)]. Comprehensive clinical, parasitological, and hematological measures were determined upon enrollment. Univariate, correlational, and hierarchical regression analyses were used to determine differences among the groups and to define predictors of worsening anemia. HIV‐1(+)/Pf(+) children had significantly more malarial pigment‐containing neutrophils (PCN), monocytosis, increased severe anemia (Hb < 6.0 g/dL), and nearly 10‐fold greater mortality within 3 months of enrollment. Common causes of anemia in malaria‐infected children, such as increased parasitemia or reduced erythropoiesis, did not account for worsening anemia in the HIV‐1(+)/Pf(+) group nor did carriage of sickle cell trait or G6PD deficiency. Hierarchical multiple regression analysis revealed that more profound anemia was associated with elevated PCM, younger age, and increasing HIV‐1 status ([HIV‐1(−) → HIV‐1(exp) → HIV‐1(+)]. Thus, malaria/HIV‐1 coinfection is characterized by more profound anemia and increased mortality, with acquisition of monocytic pigment having the most detrimental impact on Hb levels. Am. J. Hematol., 2010.