Biomedical subjects
C W Warren
Publications and source records attributed to C W Warren.
The School Health Policies and Programs Study (SHPPS): context, methods, general findings, and future efforts.
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Youth risk behavior surveillance--United States, 1993.
Priority health risk behaviors that contribute to the leading causes of mortality, morbidity, and social problems among youth and adults often are established during youth, extend into adulthood, and are interrelated. The Youth Risk Behavior Surveillance System (YRBSS) monitors six categories of priority health risk behaviors among youth and youth adults: behaviors that contribute to unintentional and intentional injuries, tobacco use, alcohol and other drug use, sexual behaviors, dietary behaviors, and physical activity. The YRBSS includes a national, school-based survey conducted by CDC and state and local school-based surveys conducted by state and local education agencies. This report summarizes results from the national survey, 24 state surveys, and nine local surveys conducted among high school students during February through May 1993. In the United States, 72% of all deaths among school-age youth and young adults are from four causes: motor vehicle crashes, other intentional injuries, homicide, and suicide. Results from the 1993 YRBSS suggest many high school students practice behaviors that may increase their likelihood of death from these four causes: 19.1% rarely or never use a safety belt, 35.3% had ridden during the 30 days preceding the survey with a driver who had been drinking alcohol, 22.1% had carried a weapon during the 30 days preceding the survey, 80.9% ever drank alcohol, 32.8% ever used marijuana, and 8.6% had attempted suicide during the 12 months preceding the survey. Substantial morbidity and social problems among adolescents also result from unintended pregnancies and sexually transmitted diseases including HIV infection.(ABSTRACT TRUNCATED AT 250 WORDS)
Seasonal differences in pregnancy outcomes: United States, 1971-1989.
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Physical activity patterns in American high school students. Results from the 1990 Youth Risk Behavior Survey.
OBJECTIVE: To assess by self-reported participation in vigorous physical activity, the quantity and quality of school physical education, team sports, and television watching among 11,631 American high school students. RESULTS: Of all students in grades 9 through 12, 37% reported engaging in 20 minutes of vigorous physical activity three or more times per week. Participation in vigorous physical activity was higher among boys than girls (P < .01) and higher among white students than among those of other races and ethnic groups (P < .01). Overall, 43.7% of boys and 52% of girls reported that they were not enrolled in physical education classes. Of the students who reported attending physical education class during the past 2 weeks, 33.2% reported exercising 20 minutes or more in physical education class three to five times per week. In contrast, rates of participation in varsity and junior varsity sports remained constant across grade levels, but participation in recreational physical activity programs showed a lesser magnitude and also decreased with advancing grade. More than 70% of students reported spending at least 1 hour watching television each school day, and more than 35% reported watching television 3 hours or more each school day. CONCLUSIONS: Participation in vigorous physical activity and physical education class time devoted to physical activity are substantially below the goals set in Healthy People 2000. As students move toward graduation, we observed disturbing declines in participation in community recreation programs and overall vigorous activity. Students appear to spend considerably more time watching television than participating in physical activity. Public health efforts should focus on increasing the physical activity levels of our youth to enhance their current well-being and to reduce the risks of future chronic disease.
Measuring adolescent sexual behaviors and related health outcomes.
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Prevalence and determinants of caesarean section in Jamaica.
The prevalence and determinants of primary caesarean section in Jamaica were estimated from a survey of women aged 14-49 years. Among 2328 women reporting 2395 live hospital births during the period January 1984 to May 1989, the prevalence of caesarean section was 4.1%. Repeat caesarean sections accounted for 1.3% of the hospital births during that period. Of the medical complications studied, prolonged labour and/or cephalopelvic disproportion carried the highest risks of primary caesarean section, followed by breech presentation, maternal diabetes, a high birth-weight baby, maternal hypertension, and a low birth-weight baby. The risk of primary caesarean section increased with maternal age, decreased with parity, was higher for urban than for rural residents, and was higher for births in private versus government hospitals.
Changes in contraceptive use and fertility: El Salvador, 1978-88.
In El Salvador from 1978 to 1988, contraceptive use among married women 15-44 years of age increased from 34% to 47%, and the total fertility rate declined from 6.3 to 4.6 children per woman. Most of this change took place from 1978 to 1985. Sterilization is the most prevalent method used, but nearly one-half of the women who are sterilized did not use any contraception before their operation. Few young couples use reversible methods of contraception to space births or delay the start of childbearing. On average, women wait 8 years after marriage and have nearly three children before they use contraception.
Catholicism and fertility in Puerto Rico.
This paper examines the association between fertility and religious affiliation among Puerto Ricans. Bongaarts' proximate determinants framework is used to compare religious categories on behaviors that directly affect fertility. We found no difference in recent fertility between Catholics and non-Catholics in Puerto Rico (total fertility rate = 2.5). We also found Catholics and non-Catholics to be similar on age at first marriage (23.3 and 23.4 years, respectively), contraceptive use (71 percent and 69 percent of married women currently contracepting), and breast-feeding practices (mean duration of breast-feeding of 4.4 and 4.3 months). Differences were observed between less committed and more committed Catholics in total fertility rate, age at first marriage, and contraceptive use, but these differences were not large and were in the opposite direction from the expected. Our findings support the theory of convergence of Catholic and non-Catholic fertility for the US. Our discrepancy with findings from the National Survey of Family Growth is evidence of the cultural diversity in the US Hispanic population and indicates the importance of disaggregating by ethnicity or national origin when studying this population.
Automated haematology: construction of univariate reference ranges for blood cell count and size.
The theory of reference ranges advocated by the International Committee for Standardization in Haematology (ICSH) was tested experimentally for an aperture impedance and a flow cytometric system. The reference sample was drawn from volunteer blood donors and the sampling procedure carefully standardised. Subjects were partitioned for gender and smoking habits, and their ages noted. Reference ranges were constructed from Gaussian statistics, after objective evaluation of the data, based on an assumed occurrence of one false positive measurement in every twenty samples. Different reference ranges were obtained on the two different systems for some haematological parameters, and partitioning also produced differences in calculated reference ranges. We conclude that strict adherence to the ICSH recommendations is almost impossible. Nevertheless, it is important that all laboratories should construct their own local reference ranges for their specific analytical systems before cost effective clinical decisions can be made.
Fertility on the US-Mexico border.
Using Bongaarts' model, the relative importance of the proximate determinants of fertility is explored in five populations on the US-Mexico border. For the groups closest to natural fertility (the two Mexican groups), lactation, use of contraception, and marriage all were moderately important in terms of their direct effect on fertility. For the group with lowest fertility (Anglo-American), contraceptive use was an important factor inhibiting fertility; marriage was important but not nearly as important as contraceptive use. For the two US Mexican-American groups, contraceptive use was an important intermediate variable, not as important as for Anglo-Americans, but more important than it was for the two populations in Mexico. The proportion married was a moderately important factor for the Mexican-American groups. For these five populations the principal differences in fertility rates result from substantial differences in the use of effective contraception. Bongaarts' model proved very useful as an analytical framework in this study.
Pregnancy and birth rates among sexually experienced US teenagers--1974, 1980, and 1983.
We examined pregnancy rates and birth rates among United States teenagers aged 15 to 19 years in 1974, 1980, and 1983. Pregnancy rate refers to live births plus induced abortions per 1000 women; birth rate refers to live births per 1000 women. We present these rates for all teens aged 15 to 19 years and for teens aged 15 to 19 years who were sexually experienced. Data sources included National Center for Health Statistics birth records, Centers for Disease Control abortion surveillance reports, and Bureau of the Census population estimates. Sexual experience estimates came from national surveys of adolescent sexual behavior. Between 1974 and 1980, the pregnancy rate among all teens increased; the pregnancy rate among sexually experienced teens declined. From 1980 to 1983, the pregnancy rate declined among all teens and among sexually experienced teens. Birth rates among US teenagers (all teens and sexually experienced teens) declined between 1974 and 1983. Whereas the decline in the birth rate from 1974 to 1980 was primarily due to increased use of abortion, the decline from 1980 to 1983 related to the decrease in teenage pregnancies.
Use of maternal-child health services and contraception in Guatemala and Panama.
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[Use of contraceptives and fertility in Panama].
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Use of maternal and child health services and immunization coverage in Panama and Guatemala.
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Platelet volume heterogeneity in acute thrombocytopenia.
Platelet volume and count were measured by aperture impedance techniques in rats during acute thrombocytopenia 2, 6, 12 and 24 h and 3, 6, 9 and 11 days after a single injection of anti-platelet serum (APS). Platelet volume heterogeneity was quantified by four statistical parameters: the measure of central tendency, dispersion, asymmetry and convexity. None of the volume distributions, including the controls, was log Gaussian. Mean platelet volume increased for the first 6 h post APS and then started to decrease although the platelet count had not started to rise. There was an initial increase, followed by a smooth decrease to control values, in the coefficient of variation (suggesting an initial increased dispersion about the mean platelet volume) with concomitant decreases in asymmetry and convexity. In contrast the age of the platelets immediately after the APS injection must have a decreased dispersion about the mean age compared with control values. These facts are used to show that young platelets are not synonymous with large platelets even under the stress of acute thrombocytopenia and support the concept that thrombopoiesis is the dominant factor in determining platelet volume heterogeneity.
Contraceptive sterilization in Puerto Rico.
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