Nonlinear Associations (nonlinear + association)

Distribution by Scientific Domains


Selected Abstracts


Serum 25-hydroxyvitamin D and IgE , a significant but nonlinear relationship

ALLERGY, Issue 4 2009
E. Hyppönen
Background:, Hormonal vitamin D system affects the determination of T-cell responses. It is unknown if there is an association between vitamin D status and allergic conditions. Our aim was to investigate differences in serum IgE concentrations by vitamin D status [measured by 25(OH)D] and by a genetic variation in a key vitamin D activation enzyme (CYP27B1) previously shown to be associated with type 1 diabetes. Methods:, 9377 participants in the 1958 British birth cohort completed a biomedical assessment at 45 years of age ; 7288 eligible participants had data on 25(OH)D and IgE, with 6429 having further information on CYP27B1 genotype (,1260C>A). Results:, There was a nonlinear association between 25(OH)D and IgE (P -value for curvature = 0.0001). Compared with the reference group with the lowest IgE concentrations [25(OH)D 100,125 nmol/l], IgE concentrations were 29% higher (95% CI 9,48%) for participants with the 25(OH)D <25 nmol/l, and 56% higher (95% CI 17,95%) for participants with 25(OH)D >135 nmol/l (adjusted for sex, month, smoking, alcohol consumption, time spent outside, geographical location, social class, PC/TV time, physical activity, body mass index and waist circumference). CYP27B1 genotype was associated with both 25(OH)D (difference for A vs. C allele: 1.88%, 95% CI 0.37,3.4%, P = 0.01) and IgE concentrations (,6.59%, ,11.6% to ,1.42%, P = 0.01). Conclusions:, These data suggest that there may be a threshold effect with both low and high 25(OH)D levels associated with elevated IgE concentrations. The same CYP27B1 allele that is protective of diabetes was associated with increased IgE concentrations. [source]


Gonadal steroids and salivary IgA in healthy young women and men

AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 3 2010
Sari M. Van Anders
Empirical evidence from clinical, nonhuman animal, and in vitro studies point to links between immune function and gonadal steroids, including potential androgenic immunosuppression and estrogenic immunoenhancement. This study was designed to test links between steroids and one marker of mucosal humoral immunity,immunoglobulin A (IgA) in healthy individuals, to facilitate comparisons with other species and clinical populations, as there are few existing studies with healthy humans that also allow gender/sex investigations. Participants (86 women, 91 men) provided a saliva sample for measurement of testosterone (T), estradiol (E2), and IgA. Results showed that E2 was significantly and positively correlated with IgA in women, and group analyses by E2 quartile showed that this association was linear. No significant correlations or nonlinear associations were seen between T and IgA in men or women, or E2 and IgA in men. Evidence from this study indicates that IgA and E2 are significantly associated in healthy premenopausal women. Am. J. Hum. Biol. 2010. © 2009 Wiley-Liss, Inc. [source]


An examination of the complementary volume,volatility information theories

THE JOURNAL OF FUTURES MARKETS, Issue 10 2008
Zhiyao Chen
The volume,volatility relationship during the dissemination stages of information flow is examined by analyzing various theories relating volume and volatility as complementary rather than competing models. The mixture of distributions hypothesis, sequential arrival of information hypothesis, the dispersion of beliefs hypothesis, and the noise trader hypothesis all add to the understanding of how volume and volatility interact for different types of futures traders. An integrated picture of the volume,volatility relationship is provided by investigating the dynamic linear and nonlinear associations between volatility and the volume of informed (institutional) and uninformed (the general public) traders. In particular, the trading behavior explanation for the persistence of futures volatility, the effect of the timing of private information arrival, and the response of institutional traders to excess noise trading risk is examined. © 2008 Wiley Periodicals, Inc. Jrl Fut Mark 28:963,992, 2008 [source]


Distances to Emergency Department and to Primary Care Provider's Office Affect Emergency Department Use in Children

ACADEMIC EMERGENCY MEDICINE, Issue 5 2009
Annameika Ludwick MD
Abstract Objectives:, Patients of all ages use emergency departments (EDs) for primary care. Several studies have evaluated patient and system characteristics that influence pediatric ED use. However, the issue of proximity as a predictor of ED use has not been well studied. The authors sought to determine whether ED use by pediatric Medicaid enrollees was associated with the distance to their primary care providers (PCPs), distance to the nearest ED, and distance to the nearest children's hospital. Methods:, This historical cohort study included 26,038 children age 18 and under, assigned to 332 primary care practices affiliated with a Medicaid health maintenance organization (HMO). Predictor variables were distance from the child's home to his or her PCP site, distance from home to the nearest ED, and distance from home to the nearest children's hospital. The outcome variable was each child's ED use. A negative binomial model was used to determine the association between distance variables and ED use, adjusted for age, sex, and race, plus medical and primary care site characteristics previously found to influence ED use. Distance variables were divided into quartiles to test for nonlinear associations. Results:, On average, children made 0.31 ED visits/person/year. In the multivariable model, children living greater than 1.19 miles from the nearest ED had 11% lower ED use than those living within 0.5 miles of the nearest ED (risk ratio [RR] = 0.89, 95% CI = 0.81 to 0.99). Children living between 1.54 and 3.13 miles from their PCPs had 13% greater ED use (RR = 1.13, 95% CI = 1.03 to 1.24) than those who lived within 0.7 miles of their PCP. Conclusions:, Geographical variables play a significant role in ED utilization in children, confirming the importance of system-level determinants of ED use and creating the opportunity for interventions to reduce geographical barriers to primary care. [source]