Childhood leukaemia in Belarus, Russia, and Ukraine following the Chernobyl power station accident: results from an international collaborative population-based case-control study.

BACKGROUND: There is little evidence regarding the risk of leukaemia in children following exposure to radionuclides from the Chernobyl Nuclear Power Plant explosion on April 26, 1986. METHODS: This population-based case-control study investigated whether acute leukaemia is increased among children who were in utero or <6 years of age at the time of the Chernobyl accident. Confirmed cases of leukaemia diagnosed from April 26, 1986 through December 31, 2000 in contaminated regions of Belarus, Russia, and Ukraine were included. Two controls were matched to each case on sex, birth year, and residence. Accumulated absorbed radiation dose to the bone marrow was estimated for each subject. RESULTS: Median estimated radiation doses of participants were <10 mGy. A significant increase in leukaemia risk with increasing radiation dose to the bone marrow was found. This association was most evident in Ukraine, apparent (but not statistically significant) in Belarus, and not found in Russia. CONCLUSION: Taken at face value, these findings suggest that prolonged exposure to very low radiation doses may increase leukaemia risk as much as or even more than acute exposure. However the large and statistically significant dose-response might be accounted for, at least in part, by an overestimate of risk in Ukraine. Therefore, we conclude this study provides no convincing evidence of an increased risk of childhood leukaemia as a result of exposure to Chernobyl radiation, since it is unclear whether the results are due to a true radiation-related excess, a sampling-derived bias in Ukraine, or some combination thereof. However, the lack of significant dose-responses in Belarus and Russia also cannot convincingly rule out the possibility of an increase in leukaemia risk at low dose levels.

Negative effect of a short interpregnancy interval on birth weight following loss of an infant to sudden infant death syndrome.

It was hypothesized that a short interpregnancy interval immediately following the birth of an infant that had succumbed to sudden infant death syndrome (SIDS) (and no other cause of death) would be associated with a reduced mean birth weight in the next infant. Mothers who had given birth to two children in the state of Oregon between 1975 and 1984 and whose first child had died in infancy from either SIDS (n = 84) or some other cause (n = 305) were identified from vital records. A multiple regression analysis in which adjustment was made for possible confounding variables (including the birth weight of the deceased child) was conducted. When the firstborn child had succumbed to SIDS, the mean birth weight of the next baby was 314 g (2,978 g vs. 3,292 g, p = 0.04) lower when the interpregnancy interval was less than 6 months versus greater than 6 months. In contrast, a less-than-6-month interval had a slightly positive effect (60 g) on the mean birth weight of the next baby when the firstborn child had died due to a cause other than SIDS. These results suggest that parents who have lost a child to SIDS may wish to delay a new pregnancy for at least 6 months.

Children's perceptions of smokers and nonsmokers: a longitudinal study.

In a longitudinal study we investigated 5th- and 7th-grade children's perceptions of smokers and nonsmokers, changes in perceptions from 5th to 7th grades, and the degree to which these perceptions predict smoking in 9th grade. The participants were 1,663 students from 14 school districts in Washington state. The results showed large developmental shifts from 5th to 7th grade in children's perceptions of both smokers and nonsmokers: Students at 7th grade saw smokers in a much more positive light and nonsmokers in a much more negative light than they did at 5th grade. Children's positive perceptions at 5th grade of smokers predicted smoking 4 years later at 9th grade and were stronger predictors than positive perceptions at 7th grade. The results suggest that smoking prevention interventions must begin before 5th grade to counter perceptions predictive of subsequent smoking.

Decreasing mortality associated with the introduction of surfactant therapy: an observational study of neonates weighing 601 to 1300 grams at birth. The Members of the National Institute of Child Health and Human Development Neonatal Research Network.

OBJECTIVE: To determine whether the introduction of surfactant therapy was associated with decreased mortality for high-risk preterm neonates weighing 601 to 1300 g at birth. DESIGN: Before-after observational study. SETTING: Eight tertiary care neonatal intensive care units participating in the National Institute of Child Health and Human Development Neonatal Research Network. PATIENTS: The outcomes for neonates with birth weight 601 to 1300 g admitted in the 2 years before surfactants became available (n = 2780) were compared with those of neonates admitted in the year beginning 2 months after surfactants became available (n = 1413). MAIN OUTCOME MEASURES: The primary outcome measure was in-hospital mortality; secondary outcome measures included durations of assisted ventilation, length of hospitalization, and neonatal morbidity. RESULTS: Forty percent of neonates in the postsurfactant group received surfactant (range 28% to 69% at the centers). Mortality decreased from 27.8% before to 19.9% after surfactant therapy was introduced (Mantel-Haenszel chi 2 = 31.4, P = .001). The adjusted odds ratio for mortality after surfactants became available was 0.73 (95% confidence interval 0.55 to 0.95). The duration of assisted ventilation and length of hospitalization increased after surfactants were introduced (P = .0001 for both outcomes). CONCLUSION: Mortality for neonates weighing 601 to 1300 g decreased after surfactant therapy was introduced, suggesting that the efficacy of surfactants demonstrated in randomized controlled trials will translate into effectiveness in routine clinical care.

Predicting mortality risk for infants weighing 501 to 1500 grams at birth: a National Institutes of Health Neonatal Research Network report.

OBJECTIVES: To develop and evaluate a model that predicts mortality risk based on admission data for infants weighing 501 to 1500 grams at birth, and to use the model to identify neonatal ICUs where the observed mortality rate differs significantly from the predicted rate. DESIGN: Validation cohort study. SETTING: University-based, tertiary care neonatal ICUs. PATIENTS: Sample of 3,603 infants with birth weights of 501 to 1500 grams who were born at seven National Institute of Child Health and Human Development (NICHHD) Neonatal Research Network Centers, over a 2-yr period of time. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Based on logistic regression analysis, admission factors associated with mortality risk for inborn infants were: decreasing birth weight, appropriate size for gestational age, male gender, non-black race, and 1-min Apgar score of < or = 3. The mortality prediction model based on these factors had a sensitivity of 0.50, a specificity of 0.92, a correct classification rate of 0.82, and an area under the receiver operating characteristic curve of 0.82 when applied to a validation sample. Goodness-of-fit testing showed that there was a marginal degree of fit between the observations and model predictions (chi 2 = 15.4, p = .06). The observed mortality rate for 3,603 infants at the seven centers was 24.7%, ranging from 21.8% to 27.7% at individual centers. There were no statistically significant differences between observed and predicted mortality rates at any of the centers. One center had an observed mortality rate that was 2.8% lower than predicted by the model (95% confidence interval -6.0% to 0.5%), and another center had an observed rate that was 3% higher than expected (95% confidence interval -0.3% to 6.2%). CONCLUSIONS: Mortality risk for infants weighing 501 to 1500 grams can be predicted based on admission factors. However, until more accurate predictive models are developed and validated and the relationships between care practices and outcomes are better understood, such models should not be relied on for evaluating the quality of care provided in different neonatal ICUs.

The effect of cesarean delivery on birth outcome in very low birth weight infants. National Institute of Child Health and Human Development Neonatal Research Network.

To determine whether cesarean delivery is associated with a better outcome than vaginal delivery for infants weighing less than 1500 g (very low birth weight), we examined neonatal mortality and the incidence of intraventricular hemorrhage (IVH) in 1765 very low birth weight inborn infants admitted to seven neonatal intensive care centers. The cesarean rate was 32.5% for infants weighing 501-750 g and 52.4% for infants weighing 751-1000 g. The neonatal death rate was 53.1% for infants weighing 501-750 g delivered by cesarean, compared with 64.3% for vaginally born infants (P = .046). However, for infants weighing 1001-1250 g, the neonatal death rate for infants delivered by cesarean was 14.4%, compared with 7.8% for infants born vaginally (P = .02). The incidence of IVH was significantly lower in infants born by cesarean than in those born vaginally only in the 1251-1500-g birth weight interval (11.8 versus 18.9%; P = .03). Compared with women delivering vaginally, those delivered by cesarean were more likely to attain a higher mean gestation, to have preeclampsia, and to have a breech presentation, and less likely to be in labor. After adjusting by logistic regression for gestational age, preeclampsia, breech presentation, presence or absence of labor, and for center effects, the odds ratio for neonatal death was 1.00 (95% confidence interval 0.71-1.41); for IVH, the odds ratio was 0.85 (95% confidence interval 0.61-1.19). These data suggest that after accounting for certain maternal and fetal factors, cesarean delivery is not associated with a lower risk of either mortality or IVH.

Demographic, knowledge, physiological, and behavioral variables as predictors of compliance with dietary treatment goals in hypertension.

The Hypertension Prevention Trial (HPT) was a multicenter, randomized trial testing calorie control, sodium restriction, and potassium increases in the prevention of hypertension in 841 men and women. Thirty four variables that were potentially related to changes in urine sodium, urine potassium, and weight were examined individually and together across 3 years of treatment and maintenance sessions. Univariate and multivariate analysis did not reveal a consistent pattern of variables associated with successful attainment of treatment goals or failure to do so. Baseline levels of urine sodium, urine potassium, and weight were the variables most consistently associated with compliance. Household composition, such as number of people living in the house or marital status and control over selection and preparation of foods, was associated with compliance in sodium reduction treatments. Number of complaints about the diets were positively associated with noncompliance. Attendance at treatment sessions was generally associated with compliance especially for weight loss. Practical implications of these results are discussed.

Relationship between socio-demographic and behaviour variables, and body mass index in a population with high-normal blood pressure: Hypertension Prevention Trial.

The relationship between socio-demographic and behaviour variables and body mass index (BMI: weight/height2) adjusted for age were studied in a population with high-normal blood pressure who participated in the Hypertension Prevention Trial. The BMI of the participants ranged from 19.1 to 35.1 kg/m2 in men and from 16.0 to 35.1 kg/m2 in women. The prevalence of obesity (BMI greater than or equal to 25.0 kg/m2) was 77 per cent in men and 61 per cent in women, with prevalence of severe obesity (BMI greater than or equal to 30.0 kg/m2) being 23 per cent and 19 per cent respectively. Stepwise regression was carried out to identify the most important correlates of BMI. In men, they were family income (+), occupation (-), leisure time exercise frequency (-), number of meals eaten out (-), alcohol intake (-), smoking (-), caffeinated drink intake (+), and meal planner. Men who planned meals with their partners had a higher BMI than men who planned their own meals or had someone else plan their meals. Correlates of little importance were marital status, race, education, number of members in household, energy intake, percentage of total calories from fat, occupation activity level, and vitamin/mineral supplement intake. In women the most important correlates of BMI were alcohol intake (-), caffeinated drink intake (+), and race. Black women had a higher mean BMI than white women. The important socio-demographic and behaviour variables in both men and women accounted for about 20 per cent of the variance in BMI which leaves about 80 per cent of the variation unexplained. This indicates the presence of other factor(s) which may be determining body weight.