Standardized risk and description of results from multivariable modeling of a binary response.

Descriptions of significant associations found from a logistic regression analysis typically are based on adjusted odds ratios. Unfortunately, odds ratios provide no information about the prevalence of response. In this paper, we justify and recommend using standardized risks, i.e., standardized probabilities, which do provide information about prevalence, in addition to adjusted odds ratios, for pairwise comparisons of the levels of a significant factor. We illustrate the advantages of generally reporting standardized risk estimates, in the context of assessing the effect of blood lead levels during the preschool years on occurrence of academic problems in kindergarten. Results are more meaningfully interpreted when accompanied by standardized risk estimates.

The risk of birth defects in multiple births: a population-based study.

OBJECTIVES: To determine if multiple births have higher risks of birth defects compared to singletons and to identify types of birth defects that occur more frequently in multiple births, controlling for seven sociodemographic and health-related variables. METHODS: A retrospective cohort study was conducted of all resident live births in Florida during 1996-2000 using data from a population-based surveillance system. Birth defects were defined as in the 9th edition of the International Classification of Diseases-Clinical Modification (ICD-9-CM) code for the 42 reportable categories in the Centers for Disease Control and Prevention (CDC) Birth Defects Registry list and eight major birth defects classifications. Relative risks (RR) before and after adjusting for control variables and 95% confidence intervals (95% CI) were calculated. The control variables included mother's race, age, previous adverse pregnancy experience, education, Medicaid participation during pregnancy, infant's sex and number of siblings. RESULTS: This study included 972,694 live births (27,727 multiple births and 944,967 singletons). Birth defects prevalence per 10,000 live births was 358.50 for multiple births and 250.54 for singletons. After adjusting for control variables, multiple births had a 46% increased risk of birth defects compared to singletons. Higher risks were found in 23 of 40 birth defects for multiple births. Five highest adjusted relative risks for birth defects among multiple births were: anencephalus, biliary atresia, hydrocephalus without spina bifida, pulmonary valve atresia and stenosis, and bladder exstrophy. Increased risks were also found in 6 out of 8 major birth defects classifications. CONCLUSIONS: Multiple births have increased risks of birth defects compared to singletons.

Sex differences in birth defects: a study of opposite-sex twins.

BACKGROUND: Sex differences in structural birth defects are often confounded by environmental risk factors. Opposite-sex twins provide a unique model for detecting sex differences in birth defects while maximally controlling environmental risk factors in a natural setting. METHODS: Population data from the Florida Birth Defects Registry were analyzed. A total of 4,768 pairs of twins who were discordant for sex and born between 1996 and 2001 were analyzed. The McNemar test was used to compare the differences between a male twin and his twin sister for the risk of developing specific defects and organ-system defects. RESULTS: Of 4,768 twin pairs, 225 males (4.72%) and 175 females (3.67%) had birth defects. Among opposite-sex twin pairs, males had a 29% higher risk for birth defects than their twin sisters. Compared to their twin sisters, males had a 5.4 times higher risk for pyloric stenosis and a 2.4 times higher risk for obstructive genitourinary defect, but only one-tenth the risk for congenital hip dislocation. CONCLUSIONS: Sex differences in birth defects exist between opposite-sex twins.

Risk factors for infant maltreatment: a population-based study.

CONTEXT: Of the approximately 900,000 children who were determined to be victims of abuse or neglect by US child protective services in 2002, the birth-to-3 age group had the highest rate of victimization (1.6%) and children younger than 1 accounted for the largest percentage of victims (9.6%). OBJECTIVE: To identify perinatal and sociodemographic risk factors associated with maltreatment of infants up to 1 year of age. DESIGN AND SETTING: Observational cohort study. PARTICIPANTS: 189,055 children born in 1996 in Florida. MAIN OUTCOME MEASURE: Infant maltreatment, defined as a verified report of abuse, neglect, or threatened harm that occurred between day 3 of life and 1 year. RESULTS: 1,602 children (.85%) of the 1996 birth cohort had verified instances of maltreatment by age 1. Of 15 perinatal and sociodemographic variables studied, 11 were found to be significantly related to infant maltreatment. Five factors had adjusted relative risks (RR) of two or greater: Mother smoked during pregnancy (RR 2.8); more than two siblings (RR 2.7); Medicaid beneficiary (RR 2.1); unmarried marital status (RR 2.0); low birth weight infant (RR 2.0). Infants who had four of these five risk factors had a maltreatment rate seven times higher than the population average. CONCLUSIONS: Data on nearly all risk factors found to be significantly associated with infant maltreatment are available on the birth certificate. Such information can be incorporated into a population-based risk-assessment tool that could identify subpopulations at highest risk for infant maltreatment. Because resources are limited, these groups should be given priority for enrollment in child abuse prevention programs.

Maternal and infant factors associated with excess kindergarten costs.

OBJECTIVE: To estimate the excess educational costs at kindergarten from infant and maternal factors that are reported routinely at birth. METHODS: Birth and school records were analyzed for all children who were born in Florida between September 1, 1990, and August 31, 1991, and entered kindergarten from 1996 through 1999 (N = 120,554). Outcome measure was cost to state, derived from base allocation for students in regular classrooms plus multiplier weights for those who were assigned to 8 mutually exclusive special education categories or who repeated kindergarten. RESULTS: More than one quarter of the study cohort was found to be assigned to special education classes at kindergarten. Regression model estimates indicated that children who were born at <1000 g (n = 380) generated 71% higher costs in kindergarten than children who were born at >or=2500 g. Children who were born at 1000 to 1499 g (n = 839) generated 49% higher costs. Other birth conditions, independent of birth weight, were associated with higher kindergarten costs: family poverty (31%), congenital anomalies (29%), maternal education less than high school (20%), and no prenatal care (14%). Because of their prevalence, family poverty and low maternal education accounted for >75% of excess kindergarten costs. If 9% of infants who weighed between 1500 and 2499 g (n = 1027) could be delivered at 2500 g, then the state of Florida potentially could save 1 million dollars in kindergarten costs. Savings of a similar magnitude might be achieved if 3% of mothers who left school without a diploma (n = 1528) were to graduate. CONCLUSIONS: Any policy recommendation aimed at reducing education costs in kindergarten must take into consideration 3 factors: the prevalence of risk conditions whose amelioration is desired, the potential cost savings associated with reducing those conditions, and the costs of amelioration. Projecting these costs from information that is available at birth can assist school districts and state agencies in allocating resources.

A population-based study of the effects of birth weight on early developmental delay or disability in children.

Improving medical treatment of extremely low-birth-weight infants over the last 20 to 30 years resulted in increased survival rates. The developmental sequela of salvaged infants is of great interest to perinatologists. The primary purposes of the current study were to assess the effect of birth weight (BW) on developmental delay or disability (DDD) in the first three years of life and determine whether there is a BW threshold below which all infants should be evaluated to determine if intervention services for children with DDD should be received. Three statewide databases were merged: 1998 Birth Vital Statistics; 1997-1998 Medicaid eligibility files; and 1998-2001 Children's Medical Services' Early Intervention Program (CMS-EIP) data. Infants who died within the first year of life and plural births were excluded. The final dataset consisted of 170,874 records. A child was determined to have a DDD if a developmental delay, or an established condition, such as sensory impairment, genetic, metabolic, neurological, or severe attachment disorders, was diagnosed through a multidisciplinary evaluation. Logistic regression models were used to relate BW to DDD, controlling for sociodemographic, behavioral, and perinatal variables. Adjusted odds ratios (OR) were calculated to describe the effects of BW on DDD. There was a significant effect of BW on DDD (Adjusted OR &equals 97.50, 40.01, 15.84, 3.29, 1.39, 1.00, 1.52 for BW categories 450-749, 750-999, 1000-1499, 1500- 2499, 2500-2999, 3000-4749, 4750-6050 g, respectively). In these categories, 70%, 56%, 36%, 11%, 4%, 3%, and 6% of surviving singleton infants, respectively, suffered a DDD in their first 3 years of life. Four medical, five sociodemographic, and two behavioral factors were significant in addition to BW. An equation for predicting the probability of DDD given these factors was obtained, and its use exemplified. BW is strongly associated with DDD. Over 60% of infants weighing < 1000 g and nearly half (46%) of those weighing < 1500 g at birth are diagnosed with a DDD before 3 years of age. The probability of DDD for a specific infant also varies by sociodemographic, other perinatal, and behavioral factors. The results of this paper suggest that all surviving infants of BW < 1000 g, and perhaps < 1500 g, should be automatically referred for evaluation.

A risk assessment screening test for very low birth weight.

OBJECTIVES: To develop a risk-assessment screening tool for very low birth weight (VLBW) and to compare our empirically derived tool to the nonempirically derived screening tool used by the State of Florida. METHODS: Birth records from the State of Florida Vital Statistics between 04/01/92 and 12/07/94 were matched with State Healthy Start prenatal records, reported from 04/01/92 through 03/31/94. Known and additional potentially important risk factors were identified from both sources. Generalized Linear Modeling techniques were used to estimate associations between risk factors and VLBW. A risk assessment system was then developed using the estimated model. The resulting screening test was compared with the one used by the Florida State Department of Health in terms of sensitivity and specificity on an independent validation sample. RESULTS: The proposed screening tool had comparable specificity to the Healthy Start screening tool but significantly better sensitivity. Both instruments are simple and easy to implement. CONCLUSIONS: Identification of women at high risk for VLBW would be improved using the model-based screening tool developed in this paper. Public health policy makers should use statistical methods in addition to expert opinion to improve existing risk assessment methods. The actual value of an improved screening instrument is dependent on the availability of effective intervention programs.