Relationship between perceived life satisfaction and adolescents' substance abuse.

PURPOSE: To explore the relationship between perceived global life satisfaction and selected substance use behaviors among 5032 public high school students. METHODS: The 1997 South Carolina Youth Risk Behavior Survey substance abuse and life satisfaction variables were used. An adjusted polychotomous logistic regression analysis utilizing SAS/SUDAAN, revealed a significant race/gender interaction. Subsequent multivariate models were constructed individually for four race/gender groups. Adjusted odds ratios and 95% confidence intervals were calculated to assess the magnitude of risk for selected substance abuse behaviors and their association with reduced global life satisfaction. RESULTS: Cigarette smoking, chewing tobacco, marijuana, cocaine, regular alcohol use, binge drinking, injection drug, and steroid use were significantly (p < .05) associated with reduced life satisfaction for specific race/gender groups (white males; black males; white females; and black females). In addition, age (< or = 13 years) of first alcohol drink, first marijuana use, first cocaine use, and first cigarette smoked were also significantly (p < .05) associated with reduced life satisfaction. CONCLUSION: Longitudinal studies are needed to determine whether dissatisfaction with life is a consequence or determinant of substance abuse behavior for adolescents.

Dietary methionine is involved in the etiology of neural tube defect-affected pregnancies in humans.

Research has provided evidence of the role of multivitamin supplementation in the prevention of neural tube defects (NTD). Failure of the neural tube to close is one of the most frequent and severe human developmental defects. The etiology of NTD is complex, encompassing genetic, dietary and environmental factors. The purpose of this study was to explore the relationship between maternal dietary intake of methionine and the risk of having a NTD-affected pregnancy. We hypothesized that women with high maternal dietary methionine intake were at a decreased risk for a NTD. Combinations of methionine, folate and vitamin B-12 intakes and NTD risk were also examined. Data from a 5-y, population-based, case-control study of 170 NTD-affected pregnancies and 269 controls were provided by the South Carolina NTD Surveillance, Prevention, and Research Project. There was a 30-55% lower NTD risk among women whose average daily dietary intake of methionine was greater than the lowest quartile of intake (>1580 mg/d). The odds ratios associated with the three quartiles of methionine intake > 1580 mg/d after adjusting for energy, race and body mass index were 0.72 (P < 0.07), 0.68 (P < 0.07) and 0.45 (P < 0.06), respectively. These findings indicate that a reduction in the risk of having a NTD-affected pregnancy is associated with maternal dietary intake of methionine (3 mo pre- to 3 mo postconception). This finding is consistent with the hypothesis that methionine plays a role in the etiology of NTD and suggests the need for further research in the area of maternal diet and pregnancy.

Relationship between life satisfaction and violent behaviors among adolescents.

OBJECTIVE: To explore relationships between life satisfaction and violent behaviors among 5,032 adolescents. METHODS: Adjusted polychotomous logistic regression analyses and multivariate models were used via SUDAAN with the 1997 CDC YRBS. RESULTS: Carrying a weapon; carrying a gun; carrying a weapon at school; physical fighting; physical fighting at school; physical fighting that required physician treatment; drinking and driving; riding with a drinking driver; having property stolen/damaged at school; feeling unsafe while at, going to or returning from school; and being injured/ threatened with a weapon were associated (p=.05) with reduced life satisfaction. CONCLUSION: Measures of life satisfaction as a component of comprehensive assessments of adolescent violence/aggression in field-work, research, and program-evaluation efforts should be considered.

Physical activity behaviors of adolescents in public and private high schools.

OBJECTIVE: To examine physical activity differences between public (PUBHS) and private (PVTHS) high school students (n = 6,627). METHODS: The 1995 SC Youth Risk Behavior Survey was utilized. Chi-square analyses compared PVTHS and PUBHS students. RESULTS: PVTHS school students reported greater involvement in regular exercise programs (p < .001) and participation on school-based sport teams (p < .001). However, PUBHS school students reported greater participation in physical education (p < .001). PUBHS males participated in more community-based sport programs than did PVTHS males (p <.001); however, PVTHS females participated in more community-based sports than PUBHS males did (p < .001). CONCLUSION: Significantly different physical activity behaviors exist between PVTHS and PUBHS students in South Carolina.

The impact of a required college health and physical education course on the health status of alumni.

The impact of a required college health and physical education course on selected health knowledge, attitudes, and behaviors of alumni was evaluated. The design was a cross-sectional study (mail out/mail back survey) using a stratified random sample of 2,000 college alumni. The overall response rate was 50%. Results were analyzed by college of graduation (college with a required health/physical education course versus no required course). Alumni who took the course were more likely to know their blood pressure, blood cholesterol, and recommended dietary fat intake than the comparison group were. They also reported that the course positively influenced their attitudes toward exercise, eating, and smoking They were more likely to engage in aerobic exercise and less likely to smoke; and they had lower intakes of dietary fat, cholesterol, and sodium. The results suggested that a required college course enhanced selected health-related knowledge, attitudes, and behaviors of alumni.

Statistical analysis for dependent dichotomous data.

The analysis of means for attributes data (ANOMAD) is used--when normal approximation applies to binomial distribution--by extending the analysis of means (ANOM) introduced by Ott and Schilling. ANOMAD compares the individual proportions or dependent percentages or set of frequencies of subjects responding to different stimuli, with the grand average of the proportions. It is interesting to see if all temporal values of some risk factors in cardiovascular diseases (CD)--acting as "stimuli"--can provide the same effect on a group of subjects by emphasizing the most important ones.

Comparison of selected health risk behaviors between adolescents in public and private high schools in South Carolina.

This study examined differences in selected health risk behaviors among 5,517 students attending public high schools (PUBHS) and 1,089 students attending private high schools (PVTHS) in South Carolina. The 1995 CDC Youth Risk Behavior Survey was used to collect self-report information on adolescent risk behaviors. Chi-square analyses were performed for comparing public and private students on selected risk behaviors. Both PUBHS and PVTHS students reported substantial involvement in most of the risk-taking behaviors examined. PUBHS students, in general, were more likely to report higher prevalence rates than PVTHS students for most of the selected health risk behaviors. However, PVTHS students reported even higher prevalence rates than PUBHS students for alcohol use, driving after drinking, and binge drinking; smoking cigarettes (past 30 days); chewing tobacco (males only); marijuana use during the past 30 days (females only); and use of alcohol or other drugs before last act of sexual intercourse. Results suggest attendance at a private high school is not a panacea for protection against adolescent risk behaviors, and that all high school students could benefit from a coordinated school health program.

The joint action of two mixed stimuli with a bivariate threshold.

The general mathematical statistical theory of a mixture of two stimuli in quantal bioassay or other binary response is investigated assuming the existence of thresholds. Univariate thresholds have long been studied. Different serious attempts on bivariate threshold theory have emerged since the late 1940s. Some have been based on biologically established fact mixed with analysis, while others have been more heuristic. In this paper we investigate the properties of correlations of thresholds. Joint actions are then interpreted according to those correlations and deviations from independence. Isoboles are lines, curves, planes, or surfaces of constant probability. They are also investigated, and their properties are used in proofs of important theorems. It is proved that additivity or additivism of two stimuli is present if and only if the thresholds of the two stimuli are perfectly correlated. Furthermore, additivity requires univariate dose-response functions to be everywhere concave on the nonnegative real numbers (doses). Finally, threshold theory, itself, dictates cumulative distributions of marginal thresholds that are everywhere nondecreasing and concave on the nonnegative reals. That is, they cannot have points of inflection. Such popular distributions as the normal and logistic have points of inflection at their respective medians. This does not invalidate their usefulness. They are simply modeling phenomena other than those which are the subject of this paper, namely, threshold theory.

Nonresponse bias in EC Respiratory Health Survey in Italy.

In the three Italian centres involved in the European Community Respiratory Health Survey (ECRHS), prevalence of asthma-like symptoms was assessed through a mailback questionnaire. Since the nonresponse rate was not negligible, ranging 10-18%, we investigated whether nonresponse bias affected the results and, if so, whether the bias could be eliminated from the final estimates of prevalence. A screening questionnaire was sent by mail to 7,000 randomly selected subjects 20-44 yrs of age, and nonresponders were contacted again by phone. Additional information was collected on a subsample of the respondents through a clinical interview. A logistic regression analysis showed that, except for one symptom (awakening for coughing), symptom prevalence significantly decreased from the first to the subsequent contact, when controlling for age, sex, centre and season of interview. The decrease in symptom prevalence was largely independent of smoking habits and socioeconomic status, and was seemingly caused by a symptom-related self-selection. When correcting results according to a linear regression model, observed estimates appeared to be slightly overestimated, by 4-10%. A simulation with the Italian data showed that the bias increased steeply at nonresponse rate higher than 30%, a situation quite common in asthma surveys. In conclusion, nonresponse bias affects the results of ECRHS in Italy, slightly inflating prevalence estimates. To make reliable comparisons on international data in the presence of different nonresponse rates, a correction of the observed prevalence seems necessary.

Black and white females' perceptions of ideal body size and social norms.

Different cultural norms and standards for appropriate female body size might contribute to the disparity in obesity rates between black and white adult females (46.0% and 24.6% respectively). The purpose of this study was to measure adolescents' perceptions of ideal size and social norms regarding female body size as well as adolescents' perceptions of significant others' evaluation and expectations of the adolescents' body size. Subjects included 437 adolescent girls (247 white and 190 black) aged 13 to 19 (x = 14.9, SD = .979) from six randomly selected public schools. The subjects, heights and weights were measured. Responses to a body image questionnaire and a series of nine female body drawings (arranged ordinally, 1 to 9, from thinnest to heaviest) were analyzed using the General Linear Model and Logistic Regression. The female body size considered ideal by black females was significantly larger than the size selected as ideal by white females (x = 3.47 and x = 3.13 respectively, p < 0.001). Black females were two times more likely than white females to describe themselves as thinner than other girls their age (O.R. = 2.01, 95% C.I. 1.34, 3.01) and seven times as likely to say that they were not overweight (O.R. = 7.08, 95% C.I. 3.72, 13.45). White females wanted to be a smaller size than they currently were and felt encouraged by significant others to lose weight or reduce their size. Black females did not indicate as great a desire as whites to be smaller and they tended to feel that their size was considered satisfactory by significant others. Only subjects from the low SES group perceived that significant others wanted them to gain weight. The differences between black and white subjects' beliefs and perceptions about body size norms may explain, in part, why heavier body weights persist in some cultural groups.

Body mass and risk of hip fracture among a national cohort of postmenopausal white women: a reanalysis.

To assess the prospective relationship between body mass and rate of hip fracture, we analyzed data from 2,285 postmenopausal women, aged 50-77 years, who responded to the first National Health and Nutrition Examination Survey (NHANES I) in 1971-1974 and the 1982-84 interview of the National Health Epidemiologic Follow-up Study (NHEFS). We plan to add to the previous analysis of these same data by Farmer et al. by 1) including retrospective information on estrogen replacement therapy; 2) increasing the follow-up time by 5 years and using only hospital-verified cases of hip fracture from the 1987 Health Care Facilities Stay data tape; and 3) limiting the analysis to postmenopausal white women, ages 50-77 years. Results of the multivariable Cox regression modeling showed that women with a baseline body mass index in the highest quartile (> 37 kg/m1.5) experienced a 70% lower rate of hip fracture compared with women in the lowest quartile (< or = 28.7 kg/m1.5)(RR=0.32; 95%CI:0.12, 0.82). Age was positively related to the risk of hip fracture, with the rate over 20% higher per year of age (RR=1.21; 95%CI:1.13, 1.29). Although reported education level, smoking history, physical activity level, and estrogen replacement were significantly (p < 0.0001) associated with body mass index, these covariates were not related to hip fracture in the multivariable analysis. Our findings corroborate earlier results using this same data source, and suggest that interventions aimed at preserving lean mass and consequent bone integrity should be encouraged among women before menopause and maintained through older adulthood.

Improved imputation of non-responses to mailback questionnaires.

Poor response rates, perhaps as low as 10 to 30 per cent, certainly bring into question the validity of any survey suffering such a malady. Repeated mailouts are capable of providing information on those persons who are resistant to responding. If one is willing to assume an exponential drop-off in response rates, then imputation is possible for the entire group of non-responders. Furthermore, a second exponential drop-off in favourable (or non-favourable) responses to particular items within the questionnaire leads to closed form estimates of population parameters and their associated standard errors. Three or more mailouts also provide a test of validity of the model assumed.

Improved rearrangement of the integrated Michaelis-Menten equation for calculating in vivo kinetics of transport and metabolism.

A multiple regression form of the integrated Michaelis-Menten equation was developed and evaluated with simulated data having controlled error. Both multiple and traditional linear regression fit errorless data perfectly, but multiple regression is much more stable with regard to accuracy and precision of estimating the Michaelis constant and maximum rate of reaction when data contain error. Bias in determining estimators of kinetic coefficients was -4 and -3% versus -56 and -35% with 10% error in the data. Multiple regression estimates for Michaelis constant and maximum rate of reaction directly as opposed to estimating 1/Km and maximum rate of reaction/Michaelis constant by linear regression. The difference in accuracy in estimating actual Michaelis constant, for example, is 4% versus 227% error with only 10% error in the data Precision of estimation is approximately the same as precision of the data for multiple regression. For the 800 data sets examined, R2 was always greater than .92 for multiple regression, but frequently was not significant for linear regression. The actual initial concentration was provided for linear regression but calculated by multiple regression with accuracy and precision equivalent to estimation of Michaelis constant and maximum rate of reaction. The multiple regression method has statistical power to determine treatment effects on Michaelis constant and maximum rate of reaction with a practical number of animals.

Clustering in sparse data and an analysis of rhabdomyosarcoma incidence.

Time series of epidemiologic events often contain periods of atypically low or high frequency. Correspondingly, for quite rate diseases there occur instances of long vacuous durations interrupted noticeably by periods of some disease activity. A recent community-based observation of the incidence of rhabdomyosarcoma (RMS), and an investigation of it, yielded sparse data of this general description. We introduce a combinatorial test for patchy time series and apply it to the RMS data. We comment on the prevalent practice of post hoc data analysis of alleged clusters, and on scale effects.

Imputing nonresponses to mail-back questionnaires.

Many mail-back questionnaires are expected at the outset to elicit poor response rates, perhaps as low as 15-30%. Corrections can be designed into such a survey by using either two or three mailouts of the questionnaire at regular intervals. Assuming a trend in responses as a function of the number of mailouts a person receives before filling out and mailing back the questionnaire, responses are imputed for those who do not mail back the questionnaire after the final mailout. Standard errors are derived, and an example is included. The imputation is easily programmed. A validation of this method is also included.

Canine corneal thickness measured by ultrasonic pachymetry.

Ultrasonic pachymetry was used to measure central, superior peripheral, and temporal peripheral corneal thicknesses of 75 dogs (150 eyes) with normal corneas, anterior chambers, and intraocular pressure. Mean corneal thickness averaged over the 2 eyes, 3 locations, and 75 dogs was 562 +/- 6.2 microns. The peripheral cornea was thicker on average than the central cornea by 49.43 +/- 8.45 microns and this difference increased with age at 6.97 +/- 1.3 microns/month of age. Mean corneal thickness changed with age (14.23 +/- 2.26 microns/month), and weight (1.83 +/- 0.38 microns/kg). Females had significantly thinner corneas (22.43 +/- 11.03 microns than males) after adjusting for age and weight.

Effect of surgical and chemical in ovo bursectomy on lymphocyte density scores and histological evaluations of primary and secondary lymphoid organs in hypertensive and hypotensive turkeys.

The effects of surgical and chemical in ovo bursectomy on the histology of primary and secondary lymphoid organs were studied in hypertensive and hypotensive lines of turkeys. The effects of bursectomy were measured by determining the presence of lymphatic nodules and the presence of lymphocytes in secondary lymphoid organs: spleen, cecal tonsil, Meckel's diverticulum, and Peyer's patches; as well as in the thymus and bursa of Fabricius. No treatment effect on splenic nodule formation occurred, but a significantly lower lymphocyte density score was present in the surgically bursectomized group. Both nodule formation and lymphocyte density scores for the cecal tonsil and Peyer's patches were significantly reduced in the surgically bursectomized and testosterone-treated groups as compared with the control and sham groups. The most consistent depression in lymphatic scores in both the surgically and chemically bursectomized groups occurred in the Peyer's patches followed by cecal tonsils and Meckel's diverticulum. As expected, there were no differences in thymocyte density scores. There was no consistent effect on lymphatic scores due to blood pressure selection; however, the hypertensive line showed significantly lower scores than the hypotensive line in the bursa, cecal tonsils, and Peyer's patches. No differences between the sexes were noted in any organ.

Effect of surgical and chemical in ovo bursectomy on hatchability, mortality rate, and antibody response in hypertensive and hypotensive lines of turkeys.

The effect of in ovo bursectomy on hatchability, mortality rate, and antibody response to keyhole limpet hemocyanin (KLH) was studied in hypertensive and hypotensive lines of turkeys. Experiments were conducted to assess the optimal time to perform surgical in ovo bursectomy in turkey embryos for the lowest mortality rate. Factors such as the ease of operation, hatchability, and least deaths were considered. Surgical bursectomies at 25, 24, 23, and 22 day embryonation resulted in 75, 20, 0, and 10% hatchability, respectively. The surgical procedure performed at 25-day embryonation resulted in superior hatchability and ease of operation, and it was less traumatic as evidenced by fewer deaths. The hatchability of embryos injected with testosterone (TE) at 15 days incubation was 55%. Birds subjected to surgery or chemical treatment had increased mortality rates. Cyclophosphamide (CY) treatment at 1 and 2 days posthatch caused a significant increase in deaths over groups not treated with CY. Both primary and secondary KLH responses were significantly lower in bursectomized and TE-injected groups, than in shamoperated or nonoperated control groups.

Controlled dosage titration of febantel paste in naturally parasitized cattle.

A controlled anthelmintic trial was conducted to determine the efficacy of febantel paste (45.5%) at dosages of 2.5, 5.0, 7.5, and 10.0 mg/kg in calves harboring natural gastrointestinal nematode infections. Dosages of 5.0, 7.5 and 10.0 mg of febantel/kg of body weight were greater than 96% effective in removing adults of Haemonchus contortus, Ostertagia spp, Cooperia spp, and Oesophagostomum radiatum. The 2.5 mg/kg dosage was considered suboptimal because of low efficacy against Ostertagia and Cooperia spp. Efficacies against Trichostronglylus axei, Trichuris spp, Bunostomum phlebotomum, and Stronglyloides papillosus were difficult to determine because fewer numbers of these nematodes were recovered. Efficacies of febantel paste against immature bovine parasites ranged from 83.62% to 97.72%.