Biomedical subjects

L M Collins

Publications and source records attributed to L M Collins.

8 recordsLinked to original sources

PubMed1991

Modeling transitions in latent stage-sequential processes: a substance use prevention example.

This article illustrates the use of latent transition analysis (LTA), a methodology for testing stage-sequential models of individual growth. LTA is an outgrowth of latent class theory and is a particular type of latent Markov model emphasizing the use of multiple manifest indicators. LTA is used to compare the fit of two models of early adolescent substance use onset and to assess the effects of a school-based substance use prevention program on Ss measured in 7th grade and again in 8th grade. Several interesting findings emerged. First, a model of substance use onset including both alcohol and tobacco use as possible starting points fit better than a model that included alcohol use as the only starting point. Second, Ss who had tried tobacco but not alcohol in in 7th grade seemed to be on an accelerated onset trajectory. Third, the normative education prevention program was generally successful, except for the students who had tried only tobacco in 7th grade.

Age Factors↗

PubMed1991

The measurement of dynamic latent variables in longitudinal aging research: quantifying adult development.

Dynamic latent variables involve systematic intraindividual change over time. Although it seems natural to apply traditional measurement theory to dynamic latent variables, in fact this is often inappropriate. Traditional measurement theory is based on the idea of static latent variables and offers little guidance to the researcher who wishes to measure a dynamic latent variable with a high degree of accuracy and validity. It is the contention of this article that measurement of a dynamic latent variable must start from a clearly defined substantive theory about human development. Two approaches that take this perspective are presented: the longitudinal Guttman simplex (LGS), a measurement model for dynamic latent variables undergoing irreversible cumulative, unitary development; and latent transition analysis (LTA), a more general latent class measurement model.

Aging↗

PubMed1990

Using the longitudinal Guttman simplex as a basis for measuring growth.

Many difficulties inherent in the measurement of growth stem from the use of traditional measurement methodologies. The longitudinal Guttman simplex (LGS), an alternative approach based on a model of growth, is discussed in this article. The LGS has several advantages over traditional methodology. First, interindividual differences in developmental rates are a part of the model. Second, the LGS procedure can easily handle any number of occasions of measurement. Third, the LGS is suited to nonlinear as well as linear monotonic growth. Fourth, a consistency index associated with the LGS methodology, CL, indicates the extent to which cumulative, unitary development characterizes a particular latent variable. Finally, and perhaps most important, because a model of the growth undergone by the latent variable being measured is incorporated in the LGS model the resulting instruments enjoy a high level of construct validity. The LGS is limited to cumulative, unitary development; additional measurement theories are needed for other kinds of development.

Child↗

PubMed1987

Frequency and adequacy of breast cancer screening among elderly Hispanic women.

Studies have demonstrated that Hispanic (relative to Anglo) women are at greater risk for late-stage breast cancer diagnosis. Screening irregularity may be a factor contributing to late-stage diagnosis, yet virtually nothing is known about the breast cancer-screening behavior of Hispanic women. We interviewed 600 elderly Hispanic women residing in Los Angeles to collect information on frequency of physician breast examinations and mammography and on regularity and competence of breast self-examination. Predictors of screening were also examined. Fifty percent of our sample indicated that they had had a breast exam within the past year; 12.5% had had a mammogram within the past year (74% never had had a mammogram); and 47% reported that they had performed breast self-examination within the past month. Few of the women were able to demonstrate adequate breast self-examination technique on a foam breast model, and only 1% found all five lumps present. Thus, although the observed frequency of screening and self-examination is comparable to national norms, it is unlikely that our subjects' attempts at self-examination would lead to early breast cancer detection. Age, educational level, emotional reactions to screening, and media cues predicted screening behavior. Physician instruction in breast self-examination increased the frequency and adequacy of self-examination. Perceived susceptibility to cancer, perceived benefits of early detection, and level of acculturation were not strong predictors. The extent to which our results generalize to other subpopulations of Hispanic women is discussed.

Aged↗

PubMed1987

The surface area of the adult human mouth and thickness of the salivary film covering the teeth and oral mucosa.

The surface area of the mouth was measured to calculate the average thickness of the salivary film which separates the opposing layers of the oral mucosa and which also overlies the dental plaque. The subjects were 10 adults of each sex, all of whom had essentially a full complement of teeth. Impressions were taken of the upper and lower jaws, the buccal and labial vestibular mucosa, and the ventral surface of the tongue, and stone models were cast. The dorsum of the tongue was assumed to have the same area as the palate plus that of the palatal surfaces of the upper teeth. The six separate areas considered were the teeth, the palate, the buccal and lingual gingival and alveolar mucosa, the buccal and labial vestibular mucosa, the ventral surface of the tongue, including the floor of the mouth, and the dorsum of the tongue. Aluminum foil, of known weight per unit area, was adapted to the models of the different regions of the mouth, and the surface areas were calculated from the weights of the foil. The mean total surface area of the mouth was 214.7 +/- 12.9 cm2, and there was no significant difference due to gender. The teeth, keratinized epithelium, and non-keratinized epithelium occupied about 20%, 50%, and 30% of the total surface area, respectively. Given that the average volumes of saliva present in the mouth before and after swallowing have been estimated to be 0.77 and 1.07 mL, respectively, it can be calculated that the average thickness of the salivary film in the mouth varies between 0.07 and 0.10 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Health behavior of elderly Hispanic women: does cultural assimilation make a difference?

The role of cultural assimilation in Hispanic health behavior has received little empirical examination. Prior studies have operationalized assimilation primarily in terms of language preference and have obtained weak or no effects. We interviewed 603 elderly Hispanic women residing in Los Angeles to evaluate the usefulness of cultural factors as predictors of preventive health behavior (e.g., physical examination, screening for breast cancer) more rigorously. Factor analysis of responses yielded four dimensions of cultural assimilation: "language preference", "country of birth", "contact with homeland", and "attitudes about children's friends." After controlling for education and age, no dimension of assimilation associated strongly or consistently with health behavior. Of the four dimensions, use of English language associated most closely with increased screening, although most of the effects for language were small in magnitude. These findings, coupled with those of other studies, strongly suggest that cultural factors may have little impact on the health behavior of Hispanics. Access to and availability of services, affective reactions toward screening, and sociodemographic factors are stronger determinants of Hispanic health practices.

Aged↗

PubMed1986

High-school smoking prevention: results of a three-year longitudinal study.

This study compared two strategies for preventing cigarette smoking among high-school students. One strategy emphasized social-pressure resistance skills, while the other focused on education about health concerns which are relevant to high-school students. Additionally, the use of same-age peer leaders and the use of familiar models in media presentations were investigated. The results suggest that social-influences resistance training was efficacious in reducing transitions to higher use by those who had previously experimented with cigarettes. Health education was most effective in preventing initial experimentation among those who had not smoked prior to the beginning of the study. Neither program was effective in limiting transitions among those who had gone beyond the experimental stage of smoking, and neither had any effect on encouraging cessation. There were no differences which could be attributed to peer leaders or to familiar media models. During later adolescence, a combined health education and social skills training approach is advocated. It is suggested that while there are some gains by implementing programs during late adolescence, prevention programs targeted at younger students may be more effective generally.

Adolescent↗

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↗