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Biomedical subjects

L M Collins

Publications and source records attributed to L M Collins.

44 records · Page 3Linked to original sources
PubMed1985

Attrition in prevention research.

Selective attrition can detract from the internal and external validity of longitudinal research. Four tests of selective attrition applicable to longitudinal prevention research were conducted on data bases from two recent studies. These tests assessed (1) differences between dropouts and stayers in terms of pretest indices of primary outcome variables (substance use), (2) differences in change scores for dropouts and stayers, (3) differences in rates of attrition among experimental conditions, and (4) differences in pretest indices for dropouts among conditions. Results of these analyses indicate that cigarette smokers, alcohol drinkers, and marijuana users are more likely to drop out than nonusers, limiting the external validity of both studies. For one project, differential rates of attrition among conditions suggested a possible attrition artifact which will interfere with interpretation of outcome results, possibly masking true program effectiveness. Recommendations for standardizing reports of attrition and for avoiding attrition through second efforts are made.

Adolescent↗
PubMed1985

Self-initiated smoking cessation among high school students.

The purpose of this study was to examine psychosocial predictors of self-initiated smoking cessation among high school students. Students from nine high schools were pretested using a questionnaire which assessed smoking behavior, beliefs about positive and negative consequences of smoking, moral attitudes toward smoking, normative expectations about smoking, rebelliousness, peer smoking and parent smoking. Smokers identified at pretest were reexamined three months and fifteen months later. Three variables, moral attitudes, peer smoking and positive beliefs about smoking significantly discriminated continuing smokers from quitters at the three-month posttest. Three different variables, negative beliefs about smoking, parental smoking and rebelliousness significantly discriminated between those who quit and later relapsed and those who quit and maintained their non-smoking status at the 15 month posttest. Smoking characteristics at pretest failed to discriminate either those who would quit or those who would maintain their non-smoking status. Results support the development of public information programs which encourage early cessation of smoking which feature the development of appropriate attitudes and beliefs and which foster social support.

Adolescent↗
PubMedDate not supplied

Distribution of cocaine and metabolites in the pregnant rat and fetus in a chronic subcutaneous injection model.

We examined the distribution of cocaine and its metabolites benzoylecgonine (BE) and norcocaine (NOR) in pregnant Sprague-Dawley rats and fetuses following twice-daily subcutaneous (s.c.) injections of 20 mg/kg cocaine HCl from gestational day (GD) 8 through GD 20. On GD 21, the animals received a single injection and maternal trunk blood, fetal blood, fetal brains, and amniotic fluid were collected 5 min, 15 min, 30 min, 1 h, 2 h, 4 h, 8 h, or 12 h later for cocaine and metabolite analyses by high-performance liquid chromatography (HPLC) with UV detection. The highest concentrations of cocaine and BE were detected in maternal plasma at 1 h and 4 h respectively. Cocaine peaked at 2 h and BE at 4 h in both fetal plasma and brain. In amniotic fluid, cocaine levels peaked at 2 h, but the highest BE levels were found at 8 h postinjection. An additional group of chronically treated dams was given both cocaine injections on GD 21 and sacrificed 2 h later. Benzoylecgonine concentrations were increased in fetal plasma, fetal brain, and amniotic fluid when compared with the 2-h results following a single cocaine treatment. Moreover, NOR, which had not been previously detected, was now measurable in the amniotic fluid.

Animals↗
PubMedDate not supplied

Analysis of stage-sequential change in rehabilitation research.

The analysis of change is a critical topic for rehabilitation outcomes research, because the goal of rehabilitation is to improve patients' function. This article will sketch the issues and problems in statistical methods for analysis of change. Recovery after serious illness or injury often has been described in terms of transitions between a series of stages, but these theories of recovery have rarely been subjected to adequate statistical examination. This article presents two methods for the analysis of change, suitable for ordinal measures of function and for testing either simple cumulative or complex multipath stage-models of recovery. Progress in medical rehabilitation will be enhanced by explicitly specifying models of recovery, measuring recovery at multiple time points, and using the resulting data to test these models empirically.

Humans↗