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Biomedical subjects

J A Bean

Publications and source records attributed to J A Bean.

62 records · Page 4Linked to original sources
PubMed1978

Menstrual cycle patterns and breast cancer risk factors.

Using a data set of women who longitudinally recorded menstrual and reproductive events, we examined menstrual cycle characteristics in relationship to early and late menarche, early and late menopause, and deferred parity, three variables epidemiologically related to breast cancer incidence. Women with late onset of menarche had longer and more variable cycles in the 10 years after menarche than did those with early onset. Women with late onset of menopause had longer and more variable cycles in the premenopausal interval than did those with early onset. Cumulative fertility in women after marriage did not differ according to cycle length and variance. Late menopause may be a breast cancer risk factor due to relative estrogen excess and progesterone lack as reflected in longer, more varied cycle patterns. Observed cycle differences between women with early and late menarche await further study of the endocrine physiology of the menstrual cycle in those groups.

Adolescent↗
PubMedDate not supplied

Mantel-Haenszel statistics and direct standardization.

This paper demonstrates that the Mantel-Haenszel chi-square statistic may be employed to test the equality of two directly standardized rates. For certain epidemiological applications, this eliminates the need for special computer programs to contrast two directly standardized rates. Furthermore, since the weights are determined entirely by the data there is the advantage of avoiding the selection of an external standard population. Data analysts who compare two groups of rates with the Mantel-Haenszel chi-square statistic may view this statistic as a comparative measure of two directly adjusted rates.

Age Factors↗
PubMedDate not supplied

Small sample behaviour of hypothesis tests related to indirect standardized rates: a Monte Carlo study.

Different distributions of confounding variables in populations complicate any comparison of the relative frequency of an event. To resolve this, methods for fitting statistical models to tables of rates have recently been developed. One such model is the multiplicative model. We performed a Monte Carlo study of the multiplicative model for a 4 X 3 table of rates. For small samples the likelihood ratio test statistic was conservative for small expected cell counts, liberal for moderate expected counts, and performed well for large expected counts. The weighted least squares test statistic was generally more conservative and less powerful than both the likelihood ratio statistic and the Pearson statistic.

Biometry↗
PubMedDate not supplied

A family study of anorexia nervosa and bulimia.

A family study is presented that examines the association between eating disorders and affective illness. 307 relatives of 30 eating disorder patients, of 16 patients with major depression, and of 20 normal controls, were interviewed to determine lifetime histories of psychiatric illness. Using logistic regression analyses, the results supported previous findings of a familial association between eating disorders and major depression. However, there was no evidence that clinical features of eating disorder patients (presence of bulimia or major depression) can be used to predict morbid risk. In addition, the results failed to reveal a familial aggregation of either alcoholism or drug abuse in eating disorder families.

Adult↗
PubMedDate not supplied

Ultrasound characterization of acoustic properties of acute intracardiac thrombi: studies in a new experimental model.

Echocardiographic differentiation among intracavitary thrombus, cavity noise, and adjacent myocardium can be difficult. As an initial step toward quantitative thrombus characterization with ultrasound, 11 dogs were studied with an in vivo intracardiac thrombus model to delineate the acoustic properties of acute thrombi. The apical coronary arteries were ligated, and subsequently injections of 5% sodium rescinoleate and 1000 units of thrombin at the endocardium-blood interface created left ventricular mural thrombi. Echocardiographic images were obtained in long- and short-axis views with a digital acquisition system, and a statistical analysis of echo intensities was performed in regions of interest in the thrombus, surrounding ventricular cavity and adjacent myocardium. Statistical measurements used to evaluate echo intensities in each region of interest included mean gray level, standard deviation, skewness, and kurtosis. The results showed that thrombus could be distinguished from myocardium (by mean gray level and standard deviation) only in short-axis views, where regions of interest could be placed at similar depths of field. Mean gray level, standard deviation, and skewness all distinguished thrombus from intracavitary blood regardless of the region of interest placement. The phase of the cardiac cycle at which data were acquired did not alter the results. We conclude that acute intracardiac thrombi can be distinguished from surrounding blood and myocardium with ultrasound tissue characterization techniques that may have the potential for clinical application.

Acoustics↗