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Risk Difference (risk + difference)
Selected AbstractsStatistical Inference For Risk Difference in an Incomplete Correlated 2 × 2 TableBIOMETRICAL JOURNAL, Issue 1 2003Nian-Sheng Tang Abstract In some infectious disease studies and 2-step treatment studies, 2 × 2 table with structural zero could arise in situations where it is theoretically impossible for a particular cell to contain observations or structural void is introduced by design. In this article, we propose a score test of hypotheses pertaining to the marginal and conditional probabilities in a 2 × 2 table with structural zero via the risk/rate difference measure. Score test-based confidence interval will also be outlined. We evaluate the performance of the score test and the existing likelihood ratio test. Our empirical results evince the similar and satisfactory performance of the two tests (with appropriate adjustments) in terms of coverage probability and expected interval width. Both tests consistently perform well from small- to moderate-sample designs. The score test however has the advantage that it is only undefined in one scenario while the likelihood ratio test can be undefined in many scenarios. We illustrate our method by a real example from a two-step tuberculosis skin test study. [source] Antibacterial efficacy of calcium hydroxide intracanal dressing: a systematic review and meta-analysisINTERNATIONAL ENDODONTIC JOURNAL, Issue 1 2007C. Sathorn Abstract Aim, To determine to what extent does calcium hydroxide intracanal medication eliminate bacteria from human root canals, compared with the same canals before medication, as measured by the number of positive cultures, in patients undergoing root canal treatment for apical periodontitis (teeth with an infected root canal system). Methodology, CENTRAL, MEDLINE and EMBASE databases were searched. Reference lists from identified articles were scanned. A forward search was undertaken on the authors of the identified articles. Papers that had cited these articles were also identified through the Science Citation Index to identify potentially relevant subsequent primary research. Review methods, The included studies were pre-/post-test clinical trials comparing the number of positive bacterial cultures from treated canals. Data in those studies were independently extracted. Risk differences of included studies were combined using the generic inverse variance and random effect method. Results, Eight studies were identified and included in the review, covering 257 cases. Sample size varied from 18 to 60 cases; six studies demonstrated a statistically significant difference between pre- and post-medicated canals, whilst two did not. There was considerable heterogeneity among studies. Pooled risk difference was ,21%; 95% CI: ,47% to 6%. The difference between pre- and post-medication was not statistically significant (P = 0.12). Conclusions, Calcium hydroxide has limited effectiveness in eliminating bacteria from human root canal when assessed by culture techniques. [source] Depressive symptoms predispose females to metabolic syndrome: a 7-year follow-up studyACTA PSYCHIATRICA SCANDINAVICA, Issue 2 2009M. Vanhala Objective:, To evaluate the risk for developing metabolic syndrome when having depressive symptoms. Method:, The prevalence of depressive symptoms and metabolic syndrome at baseline, and after a 7-year follow-up as measured with Beck depression inventory (BDI), and using the modified National Cholesterol Education Program , Adult Treatment Panel III criteria for metabolic syndrome (MetS) were studied in a middle-aged population-based sample (n = 1294). Results:, The logistic regression analysis showed a 2.5-fold risk (95% CI: 1.2,5.2) for the females with depressive symptoms (BDI ,10) at baseline to have MetS at the end of the follow-up. The risk was highest in the subgroup with more melancholic symptoms evaluated with a summary score of the melancholic items in BDI (OR 6.81, 95% CI: 2.09,22.20). In men, there was no risk difference. Conclusion:, The higher risks for MetS in females with depressive symptoms at baseline suggest that depression may be an important predisposing factor for the development of MetS. [source] Antibacterial efficacy of calcium hydroxide intracanal dressing: a systematic review and meta-analysisINTERNATIONAL ENDODONTIC JOURNAL, Issue 1 2007C. Sathorn Abstract Aim, To determine to what extent does calcium hydroxide intracanal medication eliminate bacteria from human root canals, compared with the same canals before medication, as measured by the number of positive cultures, in patients undergoing root canal treatment for apical periodontitis (teeth with an infected root canal system). Methodology, CENTRAL, MEDLINE and EMBASE databases were searched. Reference lists from identified articles were scanned. A forward search was undertaken on the authors of the identified articles. Papers that had cited these articles were also identified through the Science Citation Index to identify potentially relevant subsequent primary research. Review methods, The included studies were pre-/post-test clinical trials comparing the number of positive bacterial cultures from treated canals. Data in those studies were independently extracted. Risk differences of included studies were combined using the generic inverse variance and random effect method. Results, Eight studies were identified and included in the review, covering 257 cases. Sample size varied from 18 to 60 cases; six studies demonstrated a statistically significant difference between pre- and post-medicated canals, whilst two did not. There was considerable heterogeneity among studies. Pooled risk difference was ,21%; 95% CI: ,47% to 6%. The difference between pre- and post-medication was not statistically significant (P = 0.12). Conclusions, Calcium hydroxide has limited effectiveness in eliminating bacteria from human root canal when assessed by culture techniques. [source] Systematic review of the efficacy of antiretroviral therapies for reducing the risk of mother-to-child transmission of HIV infectionJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 3 2007N. Suksomboon PhD Summary Objective:, To evaluate the efficacy of antiretroviral therapies in reducing the risk of mother-to-child transmission of HIV infection. Methods:, Systematic review and meta-analysis of randomized controlled trials. Clinical trials of antiretrovirals were identified through electronic searches (MEDLINE, EMBASE, BIOSIS, EBM review and the Cochrane Library) up until November 2006. Historical searches of reference lists of relevant randomized controlled trials, and systematic and narrative reviews were also undertaken. Studies were included if they were (i) randomized controlled trials of any antiretroviral therapy aimed at decreasing the risk of mother-to-child transmission of HIV infection, (ii) reporting outcomes in terms of HIV infection in infant, infant death, stillbirth, premature delivery, or low birth weight. The data were extracted by a single investigator and checked by a second investigator. Disagreements were resolved through discussion or a third investigator. The efficacy was estimated using relative risk (RR), risk difference (RD) and number needed to treat (NNT) together with 95% confidence intervals. Results:, Fifteen trials were included in the systematic review. Based on five placebo-controlled trials, a zidovudine regimen reduced the risk of mother-to-child transmission by 43% (95% CI: 29,55%). The incidence of low birth weight seems to be decreased with zidovudine (pooled RR 0·75, 95% CI: 0·57,0·99). The efficacy of short-short course of zidovudine was comparable with that of the long-short course. Nevirapine monotherapy given to mothers and babies as a single dose reduced the risk of vertical transmission compared with an intrapartum and post-partum regimen of zidovudine (RR 0·60, 95% CI: 0·41,0·87). Zidovudine plus lamivudine was effective in reducing the risk of maternal-child transmission of HIV (RR 0·63, 95% CI: 0·45,0·90). Adding zidovudine to single-dose nevirapine in babies was no more effective than nevirapine alone (pooled RR 0·88, 95% CI: 0·47,1·63), nor was there any significant difference between zidovudine plus lamivudine and nevirapine. In mothers who were treated with standard antiretroviral therapy, no additional benefit was observed with the addition of a single dose of nevirapine in mothers and newborns. In addition, for mothers who received zidovudine prophylaxis, a two-dose intrapartum/newborn nevirapine reduced the risk of HIV infection and death of babies by 68% (95% CI: 39,83%) and 80% (95% CI: 10,95%), respectively, when compared with placebo. Conclusions:, The available evidence suggests that zidovudine alone or in combination with lamivudine and nevirapine monotherapy is effective for the prevention of mother-to-child transmission of HIV. They may also be beneficial in reducing the risk of infant death. Different antiretroviral regimens appear to be comparably effective in reducing HIV transmission from mothers to babies. In mothers already receiving zidovudine prophylaxis, adding a single dose of nevirapine to mothers during labour and giving the same drug to infants may further decrease the risk of vertical transmission and infant death. [source] Comparison of 1 month with 3 months of anticoagulation for a first episode of venous thromboembolism associated with a transient risk factorJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 5 2004C. Kearon Summary.,Background: The risk of recurrence is lower after treatment of an episode of venous thromboembolism associated with a transient risk factor, such as recent surgery, than after an episode associated with a permanent, or no, risk factor. Retrospective analyses suggest that 1 month of anticoagulation is adequate for patients whose venous thromboembolic event was provoked by a transient risk factor. Methods: In this double-blind study, patients who had completed 1 month of anticoagulant therapy for a first episode of venous thromboembolism provoked by a transient risk factor were randomly assigned to continue warfarin or to placebo for an additional 2 months. Our goal was to determine if the duration of treatment could be reduced without increasing the rate of recurrent venous thromboembolism during 11 months of follow-up. Results: Of 84 patients assigned to placebo, five (6.0%) had recurrent venous thromboembolism, compared with three of 81 (3.7%) assigned to warfarin, resulting in an absolute risk difference of 2.3%[95% confidence interval (CI) ,,5.2, 10.0]. The incidence of recurrent venous thromboembolism after discontinuation of warfarin was 6.8% per patient-year in those who received warfarin for 1 month and 3.2% per patient-year in those who received warfarin for 3 months (rate difference of 3.6% per patient-year; 95% CI ,,3.8, 11.0). There were no major bleeds in either group. Conclusion: Duration of anticoagulant therapy for venous thromboembolism provoked by a transient risk factor should not be reduced from 3 months to 1 month as this is likely to increase recurrent venous thromboembolism without achieving a clinically important decrease in bleeding. [source] Naratriptan for the treatment of acute migraine: meta-analysis of randomised controlled trials,PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 2 2004Darren M. Ashcroft PhD Abstract Objective To evaluate the comparative efficacy and tolerability of naratriptan in the treatment of acute attacks of migraine. Design Meta-analysis of randomised controlled trials using a random effects model. Subjects A total of 4499 patients suffering from moderate or severe attacks of acute migraine reported in ten trials. Main outcome measures Response rate ratios for headache relief, pain-free response and sustained relief (4,24 hours). Adverse events were estimated with the rate ratio (RR), risk difference and number needed to harm. Results Pooled RRs relative to placebo for pain-free response at 2 and 4 hours for naratriptan 2.5,mg were 2.52 (95%,CI: 1.78,3.57) and 2.58 (1.99,3.35). Naratriptan 2.5,mg was more effective than naratriptan 1,mg; the corresponding RRs for pain-free response at 2 and 4 hours were 1.54 (95%,CI: 1.28,1.86) and 1.35 (1.20,1.51). In contrast, naratriptan 2.5,mg was less effective in pain-free response than either rizatriptan 10,mg at 4,hours (RR: 0.68; 95%,CI: 0.55,0.85) or sumatriptan 100,mg at 4,hours (RR: 0.79; 95%,CI: 0.67,0.93). However, significantly fewer patients experienced adverse effects with naratriptan 2.5,mg than with rizatriptan 10,mg (RR: 0.73; 95%,CI: 0.56,0.97) or sumatriptan 100,mg (RR: 0.68; 95%,CI: 0.55,0.86). Conclusions Naratriptan is an effective and well-tolerated treatment for acute attacks of migraine. Head-to-head comparisons suggest that naratriptan 2.5,mg is significantly more effective than the 1,mg dose. Rizatriptan 10,mg and sumatripatn 100,mg were superior to naratriptan in terms of headache relief, while zolmitriptan 2.5,mg seemed to have comparable efficacy. Randomised controlled trials have shown that at licensed doses (1 and 2.5,mg), naratriptan is associated with a lower incidence of adverse effects than rizatriptan, sumatriptan and zolmitriptan. The incidence rates of adverse effects were similar to placebo. Copyright © 2003 John Wiley & Sons, Ltd. [source] Systematic review and meta-analysis of the adverse effects of thyroidectomy combined with central neck dissection as compared with thyroidectomy aloneTHE LARYNGOSCOPE, Issue 6 2009Edward J. Chisholm MRCS Abstract Objectives/Hypothesis: Meta-analysis to assess the increased morbidity of performing a central neck dissection with thyroidectomy to thyroidectomy alone. Study Design: Systematic review and meta-analysis. Methods: Published articles were searched for using PubMed. Suitability was assessed by using predefined inclusion/exclusion criteria. Meta-analysis on the data was performed using the Mantel-Haenszel method and a risk difference calculated. Results: Five studies with a total of 1,132 patients were included. For every 7.7 central neck dissections performed with thyroidectomy, there was one extra case of temporary hypocalcemia when compared to thyroidectomy alone. There was no significant increased risk of permanent hypocalcemia or temporary or permanent vocal cord palsy when a central neck dissection was performed in addition to a thyroidectomy. Conclusions: The benefits of prophylactic central neck dissection in differentiated thyroid carcinoma may be debated but there is no increased permanent morbidity by performing the procedure at the same time as thyroidectomy. Laryngoscope, 2009 [source] Risk factors for post-weaning mortality of Merino sheep in south-eastern AustraliaAUSTRALIAN VETERINARY JOURNAL, Issue 8 2009AJD Campbell Objective To measure associations between body weight, growth rate, sex, time of shearing and post-weaning mortality of Merino sheep. Design Uni- and multivariable survival analyses of sheep mortality during the first year after weaning, using records (n = 3657) from two field experiments conducted in Western Victoria from 1996 to 2003. Results Overall mortality was 14.3% (range 4.5,26.8%) and mean maximum mortality rate was 29 deaths/1000 weaners/month. Increased mortality risk was associated with decreases in fleece-free body weight and mean weaner growth rate, particularly at low weights and growth rates. Weaners in the lightest weaning weight quintile had a hazard ratio of 3.5, compared with the middle quintile. The hazard ratio for a 2-kg decrease in weaning weight was 1.2 to 1.7 for weaners lighter than 22 kg. The hazard ratio for a reduction in mean weaner growth rate in the first 5 months after weaning of 0.25 kg/month was 1.1 to 6.8 if mean growth rate was less than 1 kg/month, but did not differ significantly from 1 at greater growth rates. The hazard ratio for wether weaners was approximately 1.5 compared with ewe weaners. The hazard ratio for weaners shorn between December and May, compared with unshorn weaners, was 1.2 to 3.5, with the greatest risk difference associated with shearing in March (45 deaths/1000 weaners/month). Conclusion Improving the body weight and mean growth rate of weaner sheep is likely to reduce post-weaning mortality. Lightweight weaners in a flock should be managed separately from the main portion after weaning. In southern Australia, not shearing spring-born Merino weaners between December and May may assist in reducing overall post-weaning mortality. [source] Transcutaneous bilirubinometry reduces the need for blood sampling in neonates with visible jaundiceACTA PAEDIATRICA, Issue 12 2009S Mishra Abstract Objectives:, We determined usefulness of transcutaneous bilirubinometry to decrease the need for blood sampling to assay serum total bilirubin (STB) in the management of jaundiced healthy Indian neonates. Methods:, Newborns, ,35 weeks' gestation, with clinical evidence of jaundice were enrolled in an institutional approved randomized clinical trial. The severity of hyperbilirubinaemia was determined by two non-invasive methods: i) protocol-based visual assessment of bilirubin (VaB) and ii) transcutaneous bilirubin (TcB) determination (BiliCheck®). By a random allocation, either method was used to decide the need for blood sampling, which was defined to be present if assessed STB by allocated method exceeded 80% of hour-specific threshold values for phototherapy (2004 AAP Guidelines). Results:, A total of 617 neonates were randomized to either TcB (n = 314) or VaB (n = 303) groups with comparable gestation, birth weight and postnatal age. Need for blood sampling to assay STB was 34% lower (95% CI: 10% to 51%) in the TcB group compared with VaB group (17.5% vs 26.4% assessments; risk difference: ,8.9%, 95% CI: ,2.4% to ,15.4%; p = 0.008). Conclusion:, Routine use of transcutaneous bilirubinometry compared with systematic visual assessment of bilirubin significantly reduced the need for blood sampling to assay STB in jaundiced term and late-preterm neonates. (ClinicalTrials.gov number, NCT00653874) [source] A Randomized Clinical Trial to Assess the Impact on an Emergency Response System on Anxiety and Health Care Use among Older Emergency Patients after a FallACADEMIC EMERGENCY MEDICINE, Issue 4 2007Jacques S. Lee MD Abstract Objectives: Personal emergency response systems (PERSs) are reported to reduce anxiety and health care use and may assist in planning the disposition of older patients discharged from the emergency department (ED) to home. This study measured the impact of a PERS on anxiety, fear of falling, and subsequent health care use among older ED patients. Methods: This study was a randomized controlled trial comparing PERS use with standard ED discharge planning in subjects 70 years of age or older discharged home after a fall. Outcome assessors were blinded to the study objectives. Anxiety and fear of falling were measured at baseline and 30 days using the Hospital Anxiety and Depression Scale anxiety subscale (HADS-A) and modified Falls Efficacy Scale (mFES). Return to the ED, hospitalization, and length of stay were recorded after 30 and 60 days. Results: Eighty-six subjects were randomized and completed follow up (43 per group). There was no important difference in mean reduction in anxiety (mean change treatment , control, +0.35; 95% confidence interval [CI] =,1.5 to 0.76; p = 0.55) or fear of falling (mean change, +4.5; 95% CI =,6.7 to 15.7; p = 0.70). Return visits to the ED occurred in eight of 43 patients in both the control and treatment groups (risk difference, 0.0%; 95% CI =,16% to 16%). Hospitalization occurred in six of 43 in the control group versus three of 43 in the treatment group (risk difference treatment , control =,7.0%; 95% CI =,19.8% to 5.9%). Conclusions: In contrast to previous studies, there was no evidence that a PERS reduced anxiety, fear of falling, or return to the ED among older persons discharged from the ED. [source] Nasal continuous positive airway pressure versus nasal intermittent positive pressure ventilation for preterm neonates: a systematic review and meta-analysisACTA PAEDIATRICA, Issue 1 2003AG De Paoli Aim: To determine whether nasal intermittent positive pressure ventilation (NIPPV) is more effective in preterm infants than nasal continuous positive airway pressure (NCPAP) in reducing the rate of extubation failure following mechanical ventilation, and reducing the frequency of apnoea of prematurity and subsequent need for endotracheal intubation. Methods: Randomized trials of NIPPV versus NCPAP were sought and their data extracted and analysed independently by the authors using the methodology of the Cochrane Collaboration. The analysis used relative risk (RR), risk difference (RD) and number needed to treat (NNT) with 95% confidence intervals. Results: The three studies identified, comparing NIPPV with NCPAP in the postextubation period, all used synchronized NIPPV (SNIPPV), which was more effective than NCPAP in preventing failure of extubation [RR 0.21 (0.10, 0.45), RD -0.32 (-0.45, -0.20), NNT 3 (2, 5)]. Two studies compared NIPPV versus NCPAP for the treatment of apnoea of prematurity. Although meta-analysis was not possible one trial showed a reduction in apnoea frequency with NIPPV and the other a trend favouring NIPPV. Conclusion: SNIPPV is an effective method of augmenting the beneficial effects of NCPAP in preterm infants in the postextubation period. Further research is required to delineate the role of NIPPV in the management of apnoea of prematurity. [source] The financial performance of the FTSE4Good indicesCORPORATE SOCIAL RESPONSIBILITY AND ENVIRONMENTAL MANAGEMENT, Issue 1 2008David J. Collison Abstract This paper examines the financial performance of the FTSE4Good indices; the indices include companies from different geographical areas on the basis of pre-determined social responsibility criteria: currently environmental sustainability, relationships with stakeholders, attitudes to human rights, supply chain labour standards and the countering of bribery. The results indicate that over the period of analysis from 1996 to 2005 these indices outperformed their relevant benchmarks. However, most of this outperformance was due to risk differences between the FTSE4Good indices and their benchmarks. In addition, much of the outperformance arose in the period before the indices could be used by practitioners. Nevertheless, the results suggest that investors who invest in a portfolio of companies that satisfy FTSE4Good's corporate social responsibility criteria do no worse than their counterparts who do not follow a socially responsible strategy when purchasing equities. Copyright © 2007 John Wiley & Sons, Ltd and ERP Environment. [source] Which comes first: atypical antipsychotic treatment or cardiometabolic risk?ACTA PSYCHIATRICA SCANDINAVICA, Issue 3 2009S. M. Stahl Objective:, To provide an overview for practicing clinicians on the pharmacological basis of cardiometabolic risk induced by antipsychotic drugs in patients with serious mental illness, to propose hypotheses to explain these risks and to give tips for managing cardiometabolic risk during antipsychotic treatment. Method:, A MEDLINE search using terms for atypical antipsychotics (including individual drug names), metabolic, cardiovascular, weight gain and insulin resistance, cross-referenced with schizophrenia was performed on articles published between 1990 and May 2008. Results:, Strong evidence exists for significant cardiometabolic risk differences among several antipsychotic agents. Histamine H1 and serotonin 5HT2C antagonism are associated with risk of weight gain, but receptor targets for dyslipidemia and insulin resistance have not yet been identified. Convincing data indicate that hypertriglyceridemia and insulin resistance may occur in the absence of weight gain with certain antipsychotics. Conclusion:, Although lifestyle and genetics may contribute independent risks of cardiometabolic dysfunction in schizophrenia and other serious mental illness, antipsychotic treatment also represents an important contributor to risk of cardiometabolic dysfunction, particularly for certain drugs and for vulnerable patients. Mental health professionals must learn to recognize the clinical signposts indicating antipsychotic-related cardiometabolic problems to forestall progression to type II diabetes, cardiovascular events and premature death. [source] Online support for smoking cessation: a systematic review of the literatureADDICTION, Issue 11 2009Lion Shahab ABSTRACT Aim To examine the efficacy and acceptability of online, interactive interventions for smoking cessation and to identify treatment effect moderators and mediators. Methods A systematic review and meta-analysis of the literature (1990,2008) was conducted, finding 11 relevant randomized controlled trials. Data were extracted and risk ratios and risk differences estimated with a random effects model. Results There was no evidence of publication bias. Included trials were of variable methodological quality. Web-based, tailored, interactive smoking cessation interventions were effective compared with untailored booklet or e-mail interventions [rate ratio (RR) 1.8; 95% confidence interval (CI) 1.4,2.3] increasing 6-month abstinence by 17% (95% CI 12,21%). No overall effect of interactive compared with static web-based interventions was detected but there was significant heterogeneity, with one study obtaining a clear effect and another failing to find one. Few moderating or mediating factors were evaluated in studies and those that were had little effect. Pooled results suggest that only interventions aimed at smokers motivated to quit were effective (RR 1.3, 95% CI 1.0,1.7). Fully automated interventions increased smoking cessation rates (RR 1.4, 95% CI 1.0,2.0), but evidence was less clear-cut for non-automated interventions. Overall, the web-based interventions evaluated were considered to be acceptable and user satisfaction was generally high. Conclusion Interactive, web-based interventions for smoking cessation can be effective in aiding cessation. More research is needed to evaluate the relative efficacy of interactive web-based interventions compared with static websites. [source] Eating disorders in females with type 1 diabetes: an update of a meta-analysisEUROPEAN EATING DISORDERS REVIEW, Issue 4 2002Søren Nielsen Abstract Objective: Firstly to provide a quantitative summary of existing studies on the occurrence of eating disorders (ED) in females with type 1 diabetes (IDDM), with the focus on retinopathy and insulin misuse for the different eating disorders. Secondly to disseminate knowledge about useful statistical tools. Research Design and Methods: Data were extracted from the relevant case,control and follow-up studies. Odds ratios (OR) and risk differences (RD) were the main effect sizes analysed. Analyses were based on ,exact' methods as many studies are sparse. Data and findings are presented in sufficient detail for re-analysis. Results: An hypothesis of an increase in Anorexia Nervosa (AN) in IDDM is not supported by existing evidence. Bulimia Nervosa is increased (OR,=,2.9 (95%CI: 1.03 to 8.4); pOR,=,0.04) in IDDM. Both ED-NOS and subthreshold ED is increased (OR ,2; pOR,<,0.001) in females with IDDM. Co-existing ED in IDDM increases the overall common OR for retinopathy to 4.8 (95%CI: 3.0 to 7.8); pOR,<,0.00001, and the overall mean RD is 33% (95%CI: 25% to 42%); pRD,<,0.001. Insulin misuse (IM) is increased when ED co-exists with IDDM: OR 12.6 (95%CI: 7.8 to 21.1); pOR,<,0.00001, and mean RD is 40% (95%CI: 29% to 50%); pRD,<,0.001. Conclusions: ED-NOS and subthreshold ED seem to be the quantitatively most important EDs in type 1 diabetic females. Mismanagement of diabetes in the form of IM is frequent in eating disordered IDDM probands. Early occurrence of retinopathy and other complications is an increased risk in concurrent cases, as is premature death. The implications of Binge Eating Disorder (BED) and overweight needs to be elucidated for both type 1 and type 2 diabetes. Copyright © 2002 John Wiley & Sons, Ltd and Eating Disorders Association. [source] Evaluating bias due to population stratification in case-control association studies of admixed populations,GENETIC EPIDEMIOLOGY, Issue 1 2004Yiting Wang Abstract The potential for bias from population stratification (PS) has raised concerns about case-control studies involving admixed ethnicities. We evaluated the potential bias due to PS in relating a binary outcome with a candidate gene under simulated settings where study populations consist of multiple ethnicities. Disease risks were assigned within the range of prostate cancer rates of African Americans reported in SEER registries assuming k=2, 5, or 10 admixed ethnicities. Genotype frequencies were considered in the range of 5,95%. Under a model assuming no genotype effect on disease (odds ratio (OR)=1), the range of observed OR estimates ignoring ethnicity was 0.64,1.55 for k=2, 0.72,1.33 for k=5, and 0.81,1.22 for k=10. When genotype effect on disease was modeled to be OR=2, the ranges of observed OR estimates were 1.28,3.09, 1.43,2.65, and 1.62,2.42 for k=2, 5, and 10 ethnicities, respectively. Our results indicate that the magnitude of bias is small unless extreme differences exist in genotype frequency. Bias due to PS decreases as the number of admixed ethnicities increases. The biases are bounded by the minimum and maximum of all pairwise baseline disease odds ratios across ethnicities. Therefore, bias due to PS alone may be small when baseline risk differences are small within major categories of admixed ethnicity, such as African Americans. © 2004 Wiley-Liss, Inc. [source] Sex ratio and associated risk factors for 50 congenital anomaly types: Clues for causal heterogeneityBIRTH DEFECTS RESEARCH, Issue 1 2004Monica Rittler Abstract BACKGROUND Sex ratio (SR) deviations have been reported for many congenital anomalies, but so far no satisfactory explanation for these deviations has been found. The aim of this study was to detect sex-related differences in the association between risk factors and congenital anomalies, and to relate these differences with possibly underlying causes of birth defects. METHODS Between 1982 and 1999, 1,444,646 newborn infants were examined by the Estudio Colaborativo Latino Americano de Malformaciones Congénitas (ECLAMC) network of South American maternity hospitals. Male relative risks were established for 39,425 infants with 50 selected single anomalies. Associations between male sex and risk factors were identified in nonmalformed infants. In malformed infants, sex-related risk differences were established, and the SR of these infants, with and without associated risk factors, were compared. RESULTS Infants with neural tube defects (NTDs) and intrauterine growth restriction had a lower SR than those with normal growth, while spina bifida without hydrocephaly (SB[sHy]) was the only NTD subtype without a significant female predominance. Multigravidity lowered the SR of SB(sHy) and HPP (HPP) cases. Increased paternal age inverted the SR of cleft lip (CL) with or without cleft palate (CL[P]) cases from male to female. CONCLUSIONS The results indicate etiological differences between high and low SB, a stronger relationship between multigravidity and female sex of the offspring than between multigravidity and a specific congenital anomaly, and a possible involvement of dominant mutations for CL(P), as suggested by the association with increased paternal age. Birth Defects Research (Part A) 67:000,000, 2003. © 2003 Wiley-Liss, Inc. [source] | ||||||||||||||||