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Biomedical subjects

M B Bracken

Publications and source records attributed to M B Bracken.

At least 37 records · Page 2Linked to original sources
PubMed2000

Intergenerational effects of high socioeconomic status on low birthweight and preterm birth in African Americans.

As socioeconomic status (SES) increases, the incidence of low birthweight and preterm birth decreases irrespective of social class. However, low birthweight remains twice as high for African-American women as for white women even when SES is controlled. This study examines to what extent second generation high SES African-American women experience improvement in birthweight and gestational age. One hundred eighty-nine former Meharry students were surveyed. Identified were 934 births that are the children and grandchildren of these students who matriculated at Meharry. These infants are compared with a cohort of white mothers from a study in the School of Public Health at Yale University. Low birthweight was reduced in the third generation high SES African-American children (6.9%) from the second generation (11.4%) but remained higher than white children (3.3%). Results showed that African-American third generation children remained at higher risk for low birthweight than were white children (relative risk [RR], 1.78; 95% confidence interval [CI], 1.03, 3.09). Similar results were observed for preterm delivery where the increased risk to third generation African-American children was 3.16 (1.89, 5.27). Persistent strong ethnic differences in birthweight in this high SES cohort (OR = 3.16, 95% CI, 1.89-5.27) support a conclusion that African-American women have birthweight distributions that are somewhat lighter than white women. This may explain a portion of current ethnic differences in birthweight. It is also possible that persistent psychosocial and behavioral factors continue to negatively influence birthweight, even in second generation high SES African-American mothers. This explanation will require identification of powerful risk factors, which are largely unrelated to those presently under investigation.

Adult↗
PubMed1999

Environmental tobacco smoke exposure and small-for-gestational-age birth.

The aim of this analysis was to examine the effect of environmental tobacco smoke exposure on the risk of small-for-gestational-age (SGA) birth. The study population included 2,283 nonsmokers from a nested cohort study undertaken in southern Connecticut from 1988 to 1992. The duration and intensity of exposures incurred at multiple locations during the third trimester of pregnancy were measured by postpartum interview. The effect of exposure on birth weight and on incidence of SGA birth was assessed by multivariate logistic and linear regression. An estimated 26.5% of the women had been exposed to environmental tobacco smoke for at least 1 hour per week during the third trimester. The median duration of exposure among the exposed over all locations was 5 hours per week. The adjusted odds ratio for SGA birth in exposed mothers compared with unexposed mothers, using a dichotomous exposure variable, was 0.82 (95% confidence interval: 0.51, 1.33). The adjusted birth weight difference associated with exposure was -1.2 g (95% confidence interval: -43.3, 41.0). No effect of environmental tobacco smoke exposure on fetal growth was seen in this relatively homogeneous upper middle class group of women exposed at low levels. This is reassuring for women exposed at low levels, but it does not exclude the possibility of an effect in women exposed to higher levels of environmental tobacco smoke.

Adult↗
PubMed1999

Interpregnancy interval and disparity in term small for gestational age births between black and white women.

OBJECTIVE: To examine the influence of interpregnancy interval on the elevated risk of term small for gestational age (SGA) births to black women. METHODS: This study is a secondary analysis of data from the Delivery Interview Program, a hospital-based cohort study of 12,718 women conducted at the Boston Hospital for Women from 1977 to 1980. The current analysis was limited to black and white parous women who gave birth to term infants during the study and whose last previous pregnancies had also resulted in term, live births. There were 578 black and 3400 white women who met these criteria. The rates of term SGA births for black and white women were calculated according to six interpregnancy intervals (6 or less, 6-12, 12-24, 24-36, 36-60, or longer than 60 months). Multiple logistic regression was used to control for confounding. RESULTS: The overall rate of term SGA births was 6.4% for black women compared with 3.9% for white women (relative risk [RR] 1.7, 95% confidence interval [CI] 1.2, 2.4). Black women were also more likely than white women to have interpregnancy intervals of 6 months or less (9.2% black, 4.8% white; RR 1.9, 95% CI 1.4, 2.6). At every interpregnancy interval, black women had a higher rate of term SGA births than white women. After controlling for interpregnancy interval in a logistic regression analysis, the increased risk of SGA delivery among black women remained unchanged (odds ratio 1.7, 95% CI 1.1, 2.5). CONCLUSION: Although black women were more likely than white women to have SGA births and short interpregnancy intervals, differences in interpregnancy intervals between the races did not explain the disparity in term SGA births.

Adolescent↗
PubMed1999

Methodological issues in the study of rare exposures and rare outcomes in perinatal epidemiology.

Epidemiologic study of rare exposures and rare outcomes is complicated. For perinatal epidemiology, a prospective cohort study design is preferred for reproductive outcomes with incidences of at least 5%. Case-control studies are generally used to investigate rare outcomes with incidences from 5 per 1000 to less than 1 per 1000. However, obtaining data on large numbers of rare cases can be difficult. The use of nested case-control designs or nested prospective studies may be particularly useful in perinatal epidemiology.

Epidemiologic Studies↗
PubMed1999

Magnetic resonance imaging and neurological recovery in acute spinal cord injury: observations from the National Acute Spinal Cord Injury Study 3.

STUDY DESIGN: Data are from a multicenter, randomized, double blind clinical trial of acute spinal cord injury. OBJECTIVES: To evaluate the prognostic value of magnetic resonance imaging (MRI) for randomized patients in the National Acute Spinal Cord Injury Study 3 (NASCIS). SETTING: Sixteen spinal cord injury centers throughout the United States and Canada. METHODS: Of 499 patients randomized in NASCIS 3 between December 1991 and September 1995, MRI was electively done on 191 patients within 72 h of injury. Indications of hemorrhage, edema, and contusion were recorded by standard protocol. Neurological impairment as determined by motor function, response to pin prick and light touch was assessed at admission to the participating center and 6 weeks after injury. Change in neurological function was obtained by subtracting the score of each neurological parameter at admission from that measured at 6 weeks. Spinal cord surgery performed within the 3 days after injury was noted. Data were analyzed by: chi square, analysis of variance, multiple logistic regression and linear regression models. RESULTS: Patients with hemorrhage were much more likely to have a complete injury (OR=2.88, 95 Cl 1.32, 6.23); however this association was much reduced when the initial neurological examination was taken into account (AOR=1.43, 95% Cl 0.55, 3.73) and was no longer a significant predictor of injury. MRI evidence of cord edema was the strongest predictor of reduced improvement in motor function (-3.34 points, P=0.06) and light touch sensation (-3.41 points, P=0.05) at 6 weeks. CONCLUSIONS: Cord hemorrhage, contusion, and edema on MRI were not associated with diagnosis of a complete cord injury after neurological assessment from the initial clinical examination was taken into account. Prediction of a worse 6 week neurological status was weakly associated with the presence of edema diagnosed by MRI. As MRI technology improves, these diagnostic and predictive capabilities need to be re-assessed. SPONSORSHIP: NASCIS 3 was funded by the National Institute of Neurological Disorders and Stroke at the National Institutes of Health, Washington, DC, USA. Pharmacia and Upjohn provided study drugs and placebos; they also monitored data quality, and funded additional tests, in accordance with Food and Drug Administration regulatory requirements. Dr Bracken has served as an occasional paid consultant to Pharmacia and Upjohn.

Adolescent↗
PubMed1999

Healthy women's PEF variations with ambient summer concentrations of PM10, PM2.5, SO42-, H+, and O3.

The relationship between ambient air pollution and daily change in peak expiratory flow (PEF) was studied in a sample of 473 nonsmoking women (age 19 to 43 yr) in Virginia over summers 1995- 1996. Daily 24-h averages of particulate matter (PM2.5 and PM10), fine particulate sulfate (SO42-) and strong acid (H+), hourly ozone (O3), and select meteorologic variables (e.g., temperature) were collected at a regional outdoor monitoring site. Subjects took PEF measurements twice daily for a 2-wk period using a standard MiniWright peak flow meter. Concurrent measures for summer periods of 24-h PM2.5 (micrograms/m3) ranged from 3.5 to 59.7; H+ (nmol/m3) from 0 to 250; maximal daily 8-h average O3 (ppb) from 17.0 to 87.6. Morning PEF decrements were significantly associated with H+ and PM2. 5. An increase of 50 etamol/m3 of H+ and 10 micrograms/m3 of PM2.5 related to decreases of 0.89 (95% CI = 0.21 to 1.57) and 0.73 (95% CI = 0.07 to 1.38) L/min in morning PEF, respectively. Ozone was the only exposure related to evening PEF with 5-d cumulative lag exposure showing the greatest effect; 7.65 L/ min (95% CI = 2.25 to 13.0) decrease per 30 ppb O3 increase. Separate physiologic effects were observed for summer ambient concentrations of two different pollutants (PEF decrements related to PM2.5 in morning and O3 in evening) at concentrations below the new U.S. EPA 24-h ambient air quality standard for PM2.5 and 8-h standard for O3.

Adult↗
PubMed1998

Correlates of residential wiring code used in studies of health effects of residential electromagnetic fields.

The home wiring code is the most widely used metric for studies of residential electromagnetic field (EMF) exposure and health effects. Despite the fact that wiring code often shows stronger correlations with disease outcome than more direct EMF home assessments, little is known about potential confounders of the wiring code association. In a study carried out in southern Connecticut in 1988-1991, the authors used strict and widely used criteria to assess the wiring codes of 3,259 homes in which respondents lived. They also collected other home characteristics from the tax assessor's office, estimated traffic density around the home from state data, and interviewed each subject (2,967 mothers of reproductive age) for personal characteristics. Women who lived in very high current configuration wiring coded homes were more likely to be in manual jobs and their homes were older (built before 1949, odds ratio (OR) = 73.24, 95% confidence interval (CI) 29.53-181.65) and had lower assessed value and higher traffic densities (highest density quartile, OR = 3.99, 95% CI 1.17-13.62). Because some of these variables have themselves been associated with health outcomes, the possibility of confounding of the wiring code associations must be rigorously evaluated in future EMF research.

Adult↗
PubMed1998

Alarums false, alarums real: challenges and threats to the future of epidemiology.

PURPOSE: A review of recent threats and challenges to epidemiology suggests that some represent an opportunity to advance the discipline while others are a major threat to conducting epidemiologic work. METHODS: Two issues are identified which should advance the publication and conduct of epidemiologic research. Three are discussed that exemplify current threats. RESULTS: Epidemiologists have a role in helping journalists improve the communication of risk information in the media. Methodological advances for studies of rare exposure being related to rare disease should reduce the frequency of conflicting results in the epidemiologic literature. Three significant external forces that threaten epidemiologic research are identified. These are: unbridled discovery during litigation as exemplified by Bendectin, breast implants and cellular telephones; over zealous privacy laws; and the negative impact of managed care on epidemiologic research. CONCLUSIONS: The American College of Epidemiology has a major role to play in protecting the profession from some of the real threats that face it, and in helping meet the challenges.

Antiemetics↗
PubMed1998

Maternal anthropometric factors and risk of primary cesarean delivery.

OBJECTIVES: This study examined absolute and proportional gestational weight gain and prepregnancy body mass index as predictors of primary cesarean delivery. METHODS: Data were derived from a prospective study of pregnancy outcome risk factors in 2301 women in greater New Haven, Conn, who had singleton deliveries by primary cesarean (n = 312) or vaginal delivery (n = 1989) and for whom height, prepregnancy weight, and weight gain were available. Women were divided into 4 body mass index groups (underweight, low average, high average, and obese) and further subdivided into 8 groups according to median proportional or absolute weight gain. RESULTS: Risk of cesarean delivery increased with increasing body mass index and gestational weight gain greater than the median for one's body mass index. Proportional weight gain was more predictive of cesarean delivery than absolute weight gain. Underweight women gaining more than 27.8% of their prepregnancy weight had a 2-fold adjusted relative risk of cesarean delivery. CONCLUSIONS: Proportional weight gain is an important predictor of cesarean delivery for underweight women; high body mass index is also predictive of increased risk.

Adult↗
PubMed1998

Methylprednisolone or tirilazad mesylate administration after acute spinal cord injury: 1-year follow up. Results of the third National Acute Spinal Cord Injury randomized controlled trial.

OBJECT: A randomized double-blind clinical trial was conducted to compare neurological and functional recovery and morbidity and mortality rates 1 year after acute spinal cord injury in patients who had received a standard 24-hour methylprednisolone regimen (24MP) with those in whom an identical MP regimen had been delivered for 48 hours (48MP) or those who had received a 48-hour tirilazad mesylate (48TM) regimen. METHODS: Patients for whom treatment was initiated within 3 hours of injury showed equal neurological and functional recovery in all three treatment groups. Patients for whom treatment was delayed more than 3 hours experienced diminished motor function recovery in the 24MP group, but those in the 48MP group showed greater 1-year motor recovery (recovery scores of 13.7 and 19, respectively, p=0.053). A greater percentage of patients improving three or more neurological grades was also observed in the 48MP group (p=0.073). In general, patients treated with 48TM recovered equally when compared with those who received 24MP treatments. A corresponding recovery in self care and sphincter control was seen but was not statistically significant. Mortality and morbidity rates at 1 year were similar in all groups. CONCLUSIONS: For patients in whom MP therapy is initiated within 3 hours of injury, 24-hour maintenance is appropriate. Patients starting therapy 3 to 8 hours after injury should be maintained on the regimen for 48 hours unless there are complicating medical factors.

Activities of Daily Living↗
PubMed1998

Spontaneous abortion and exposure to electric blankets and heated water beds.

We conducted a prospective study (N = 2,967) to evaluate the relation of spontaneous abortion with use of electrically heated beds (electric blankets and heated water beds) during pregnancy. At interview, 61.5% of women were at less than 12 weeks gestation, and 38.5% were between 13 and 16 weeks; thus, very early pregnancy losses would have been excluded. Information regarding exposure to electric beds was obtained for the month of conception and the 7 days before interview. Electric blanket use at conception was associated with an increased risk of spontaneous abortion in the unadjusted analysis [relative risk (RR) = 1.84; 95% confidence interval (CI) = 1.08-3.13], but adjustment for other factors reduced the risk slightly [odds ratio (OR) = 1.74; 95% CI = 0.96-3.15]. Heated water bed use was not associated with an increased risk of spontaneous abortion at conception (OR = 0.59; 95% CI = 0.33-1.07) or at interview (OR = 0.63; 95% CI = 0.36-1.12). Measures of dose response (daily use, hours of use, or temperature setting) were not associated with increased risk. Wire code data were obtained for the first, or only, house lived in during pregnancy. Women living in homes classified as "very high" or "ordinary high" current configuration were not at greater risk than women living in homes with buried wires. Nor was there any trend for increased risk of spontaneous abortion by wire code category. This study does not support the hypothesis that use of electric beds or residence in a high current configuration home increases the risk of spontaneous abortion; however, it indicates that electric blanket use at the time of conception and in early pregnancy may be associated with a slight increase in risk of pregnancy loss.

Abortion, Spontaneous↗
PubMed1997

Administration of methylprednisolone for 24 or 48 hours or tirilazad mesylate for 48 hours in the treatment of acute spinal cord injury. Results of the Third National Acute Spinal Cord Injury Randomized Controlled Trial. National Acute Spinal Cord Injury Study.

OBJECTIVE: To compare the efficacy of methylprednisolone administered for 24 hours with methyprednisolone administered for 48 hours or tirilazad mesylate administered for 48 hours in patients with acute spinal cord injury. DESIGN: Double-blind, randomized clinical trial. SETTING: Sixteen acute spinal cord injury centers in North America. PATIENTS: A total of 499 patients with acute spinal cord injury diagnosed in National Acute Spinal Cord Injury Study (NASCIS) centers within 8 hours of injury. INTERVENTION: All patients received an intravenous bolus of methylprednisolone (30 mg/kg) before randomization. Patients in the 24-hour regimen group (n=166) received a methylprednisolone infusion of 5.4 mg/kg per hour for 24 hours, those in the 48-hour regimen group (n=167) received a methylprednisolone infusion of 5.4 mg/kg per hour for 48 hours, and those in the tirilazad group (n=166) received a 2.5 mg/kg bolus infusion of tirilazad mesylate every 6 hours for 48 hours. MAIN OUTCOME MEASURES: Motor function change between initial presentation and at 6 weeks and 6 months after injury, and change in Functional Independence Measure (FIM) assessed at 6 weeks and 6 months. RESULTS: Compared with patients treated with methylprednisolone for 24 hours, those treated with methylprednisolone for 48 hours showed improved motor recovery at 6 weeks (P=.09) and 6 months (P=.07) after injury. The effect of the 48-hour methylprednisolone regimen was significant at 6 weeks (P=.04) and 6 months (P=.01) among patients whose therapy was initiated 3 to 8 hours after injury. Patients who received the 48-hour regimen and who started treatment at 3 to 8 hours were more likely to improve 1 full neurologic grade (P=.03) at 6 months, to show more improvement in 6-month FIM (P=.08), and to have more severe sepsis and severe pneumonia than patients in the 24-hour methylprednisolone group and the tirilazad group, but other complications and mortality (P=.97) were similar. Patients treated with tirilazad for 48 hours showed motor recovery rates equivalent to patients who received methylprednisolone for 24 hours. CONCLUSIONS: Patients with acute spinal cord injury who receive methylprednisolone within 3 hours of injury should be maintained on the treatment regimen for 24 hours. When methylprednisolone is initiated 3 to 8 hours after injury, patients should be maintained on steroid therapy for 48 hours.

Adolescent↗
PubMed1997

Systematic reviews of medical evidence: the use of meta-analysis in obstetrics and gynecology.

OBJECTIVE: To review the technique of meta-analysis and its uses and limitations in obstetrics and gynecology. DATA SOURCES: We reviewed four major journals in obstetrics and gynecology (American Journal of Obstetrics and Gynecology, Fertility and Sterility, Journal of Reproductive Medicine, and Obstetrics & Gynecology). METHODS OF STUDY SELECTION: Journals were reviewed to determine frequency of meta-analysis as a method of systematic review in obstetrics and gynecology. We also summarized objectives and scientific guidelines for performing a meta-analysis. TABULATION, INTEGRATION, AND RESULTS: Meta-analysis is used with increased frequency in obstetrics and gynecology as a way of systematically reviewing medical evidence. This technique is an attempt to improve on traditional methods of narrative review by an expert and as a framework for evidence-based medicine and developing practice guidelines. By combining data from replicate studies, a meta-analysis can increase statistical power, more precisely estimate the typical effect size of treatment or risk factor, and attempt to resolve controversies in the medical literature. Meta-analysis is a retrospective look at data already collected and is therefore subject to the biases of all retrospective studies. CONCLUSIONS: The technique of meta-analysis requires all the scientific rigor of a randomized clinical trial with careful attention to study design, including a formal protocol for literature search strategies, quality assessment of candidate studies, specific inclusion and exclusion criteria, issues of sampling and publication bias, statistical tests of homogeneity, and sensitivity analysis.

Evidence-Based Medicine↗
PubMed1997

Low-to-moderate gestational alcohol use and intrauterine growth retardation, low birthweight, and preterm delivery.

PURPOSE: Heavy drinking during pregnancy is an established risk factor for fetal alcohol syndrome and other adverse perinatal outcomes. However, there is still debate as to the effects of low-to-moderate drinking during pregnancy. METHODS: This prospective investigation was based on 2714 singleton live births at Yale-New Haven Hospital during 1988-1992. Alcohol drinking during pregnancy was evaluated with respect to intrauterine growth retardation (IUGR), preterm delivery, and low birthweight. RESULTS: Mild drinking, defined as > 0.10-0.25 oz of absolute alcohol per day, during the first month of pregnancy was associated with a protective effect on IUGR (OR, 0.39; 95% confidence interval (CI), 0.20-0.76). Overall, drinking during month 1 of pregnancy suggested a curvilinear effect on growth retardation, with consumption of > 1.00 oz of absolute alcohol per day showing increased risk. Drinking during month 7 was associated with a uniform increase in the odds of preterm delivery; the ORs were 2.88 (95% CI, 1.64-5.05) for light drinking and 2.96 (95% CI, 1.32-6.67) for mild-to-moderate alcohol consumption. CONCLUSIONS: Differences in the risk estimates for IUGR and preterm delivery may indicate etiological differences that warrant further investigation of these outcomes and critical periods of exposure. Low birthweight is not a useful neonatal outcome for this exposure because it is a heterogeneous mix of preterm delivery and IUGR. Despite the observed protective effects of mild drinking on IUGR, the increased risk of preterm delivery with alcohol use supports a policy of abstinence during pregnancy.

Adult↗