Search PubMed⌕ Search

Biomedical subjects

J A Baron

Publications and source records attributed to J A Baron.

At least 145 records · Page 8Linked to original sources
PubMed1991

Cigarette smoking, body mass and other risk factors for fractures of the hip in women.

Determinants of hip fractures were assessed using data from a network of hospital-based case-control studies from northern Italy. For the present analysis, cases were 209 women with fractures of the hip/proximal femur (aged 29 to 74, median age 62) admitted to a network of teaching and general hospitals in the greater Milan area; controls were 1449 women, aged 25 to 74 (median age 55), admitted for non-traumatic, acute conditions to the same network of hospitals. There was a strong direct association with smoking, the relative risk (RR) being significantly and similarly elevated both in ex- and in current smokers (RR 1.7 and 1.5 respectively) which rose to 2.4 for 25 or over cigarettes per day. The risk was associated with duration of smoking and apparently greater in post-menopausal women. Two factors showed significant inverse associations with hip fractures: relative weight, with relative risks of 0.5, 0.4 and 0.3 in subsequent categories of body mass index as compared with thinner ones, and the use of oestrogen replacement treatment (multivariate RR = 0.4, 95% confidence interval (CI): 0.2-1.1). No association was observed with education or social class, selected indicator foods or alcohol consumption (RR for the highest consumption level = 1.0). The effects of smoking and body mass index appeared independent: compared with never smoking heavier women, the RR for smoking thin women was 4.6. Thus, this case-control study of hip fractures in a predominantly post-menopausal population of Italian women showed a strong association with smoking and appreciable protection from heavier body mass index and the use of oestrogen replacement treatment.

Adult↗
PubMed1991

Hip fracture incidence and mortality in New England.

We used Medicare data to conduct a population-based study of osteoporotic hip fracture incidence and outcomes among New England residents. To reduce bias and improve data reliability, we combined data from multiple files; we found that 6% of cases would have been missed had we relied on hospital claims alone. Hip fracture incidence (per 1,000 person-years) increased for white females from 2.2 for ages 65-69 to 31.8 for ages 90-94 and for white males from 0.9 for ages 65-69 to 20.8 for ages 90-94. Incidence among blacks was lower in all age/sex groups. The female/male relative risk was greater among whites than among blacks. Case fatality following hip fracture was 12.5% at 90 days and 23.7% at 1 year and was higher among males, older patients, and those who had documented comorbidity or who were residents of nursing homes.

Age Factors↗
PubMed1990

Effect of intravenous streptokinase on early mortality in patients with suspected acute myocardial infarction. A meta-analysis by anatomic location of infarction .

PURPOSE: To determine the effect of intravenous streptokinase on early mortality in patients with suspected acute anterior and acute inferior myocardial infarctions. DATA IDENTIFICATION: A literature search of English-language studies on the use of intravenous streptokinase in the treatment of suspected acute myocardial infarction for the period 1966 to 1989 using Medlars II and the bibliographies of relevant articles. In a number of instances, additional details on early mortality by location of myocardial infarction were provided by the authors. STUDY SELECTION: Of 140 originally identified articles, 6 that specifically met our inclusion criteria were selected: randomized trials that used intravenous streptokinase in a dose of 1.5 million units, with or without additional agents, compared with a group that differed only by the absence of streptokinase. Trials were selected by review of the methods section without regard for the results. DATA EXTRACTION: Data were extracted independently by two observers using specific methodologic criteria for infarct location and early mortality. After they conferred, the observers agreed completely on the data. RESULTS OF DATA SYNTHESIS: Among the 9155 patients with suspected acute anterior myocardial infarction, the mortality rate in the control group was 17.4%. In contrast, patients treated with streptokinase had a 12.5% mortality. The mean risk difference was -4.8% (95% CI, -7.5% to -2.1%) and the summary risk ratio was 0.72 (CI, 0.65 to 0.79). A total of 9650 patients with suspected inferior infarction had a mortality rate in the control group of 7.6% [corrected]. The mortality for streptokinase-treated patients was 6.6%. The mean risk difference was -0.8% (CI, -1.8% to 0.2%) and the summary risk ratio was 0.87 (CI, 0.76 to 1.01). CONCLUSIONS: Intravenous streptokinase clearly confers a protective effect against early mortality in patients with suspected acute anterior myocardial infarction. The magnitude of this effect is on the order of a 5% absolute reduction in risk of death by 21 to 35 days. For these patients, 21 need to be treated to save 1 additional life. For patients with suspected acute inferior infarction, the benefit of treatment on reducing early mortality is of smaller magnitude and less certain. These patients have an estimated absolute reduction of early mortality of approximately 1%, which would require treating 125 patients to save 1 additional life.

Humans↗
PubMed1990

A clinical trial of beta carotene to prevent basal-cell and squamous-cell cancers of the skin. The Skin Cancer Prevention Study Group.

BACKGROUND: Beta carotene has been associated with a decreased risk of human cancer in many studies employing dietary questionnaires or blood measurements, and it has had protective effects in some animal models of carcinogenesis. METHODS: We tested the possible cancer-preventing effects of beta carotene by randomly assigning 1805 patients who had had a recent nonmelanoma skin cancer to receive either 50 mg of beta carotene or placebo per day and by conducting annual skin examinations to determine the occurrence of new nonmelanoma skin cancer. RESULTS: Adherence to the prescribed treatment was good, and after one year the actively treated group's median plasma beta carotene level (3021 nmol per liter) was much higher than that of the control group (354 nmol per liter). After five years of follow-up, however, there was no difference between the groups in the rate of occurrence of the first new nonmelanoma skin cancer (relative rate, 1.05; 95 percent confidence interval, 0.91 to 1.22). In subgroup analyses, active treatment showed no efficacy either in the patients whose initial plasma beta carotene level was in the lowest quartile or in those who currently smoked. There was also no significant difference between treated and control groups in the mean number of new nonmelanoma skin cancers per patient-year. CONCLUSIONS: In persons with a previous nonmelanoma skin cancer, treatment with beta carotene does not reduce the occurrence of new skin cancers over a five-year period of treatment and observation.

Aged↗
PubMed1990

The antiestrogenic effect of cigarette smoking in women.

Epidemiologic results indicate that women who smoke cigarettes are relatively estrogen-deficient. Smokers have an early natural menopause, a lowered risk of cancer of the endometrium, and an increased risk of some osteoporotic fractures. Moreover, women who smoke may have a reduced risk of uterine fibroids, endometriosis, hyperemesis gravidarum, and benign breast disease. Several possible mechanisms for these effects have been identified. Smoking does not appear to be clearly related to estradiol levels, at least in postmenopausal women, although levels of adrenal androgens are increased. Moreover, smoking appears to alter the metabolism of estradiol, leading to enhanced formation of the inactive catechol estrogens.

Breast Neoplasms↗
PubMed1990

Cigarette smoking and the risk of natural menopause.

We reviewed published studies on the association of age at natural menopause and cigarette smoking. All demonstrated an earlier median or mean age of menopause among smokers; for current smokers vs noncurrent smokers the difference ranged from 0.8 to 1.7 years. For studies that presented suitable data, we computed prevalence odds ratios of menopause for current smokers vs never-smokers, current smokers vs noncurrent smokers, and former smokers vs never-smokers. The Mantel-Haenzel summary odds ratios and 95% confidence intervals for these contrasts were: 1.9 (1.7-2.2), 1.7 (1.5-1.9), and 1.3 (1.0-1.7). Studies that presented data on amount of cigarettes smoked per day demonstrated "dose-response" trends when analyzed using the Mantel-Haenszel extension. The consistency of results across studies, the persistence of the effect when age and other covariates were considered, and the dose-response relation all support the hypothesis that smoking increases the risk of early menopause.

Adult↗
PubMed1990

Pulmonary sequelae in survivors of congenital diaphragmatic hernia.

Nineteen survivors of congenital diaphragmatic hernia repair were compared with age and sex matched control children six to 11 years after repair. All subjects were examined clinically and underwent lung function testing. The patients also had individual lung volumes assessed radiographically and had radionuclide (krypton-81 m, technetium-99 m macroaggregates) ventilation-perfusion (V/Q) lung scans. Four patients had pectus excavatum and two had mild scoliosis. Spirometric measurements were lower in the patients than in the control subjects but only the differences in peak expiratory flow and flow at 50% of expired vital capacity were significant. The radiographic left lung volumes in patients surviving left diaphragmatic repair were larger than expected at 49.3% (SD 2%), suggesting alveolar overdistension. V/Q scans showed a mismatch in the ipsilateral lung, mean Q (40% (7%] being significantly lower than mean V (47% (6%)). In seven patients who had required ventilation for four days or more perfusion to the ipsilateral lung was significantly lower (34% (6%)) than values for the 12 patients ventilated for less than four days (43% (6%)). Survivors of right diaphragmatic repair had a better outcome in terms of relative radiographic lung volumes and V/Q distribution. More severely affected children are now surviving repair of congenital diaphragmatic herniation, with residual pulmonary abnormalities that could produce functional impairment in adult life.

Child↗
PubMed1990

Overcoming potential pitfalls in the use of Medicare data for epidemiologic research.

We used Medicare data bases and US Census data to address two questions critical to the use of Medicare files for epidemiologic research. First, we examined the degree to which the population enrolled in the Medicare program is similar to the elderly resident population of the United States, as estimated by the US Census. We found small differences in the total population estimates but substantial differences by age and race. Second, we found that among Medicare enrollees, physician claims identify a small proportion of hip fracture cases which are not documented in the hospital discharge files. This proportion varies by age, region, and state within the United States. Calculation of rates based on Medicare hospital discharge data, and probably other hospital discharge data sets as well, must take these limitations into account. Use of all available Medicare data files can overcome these limitations.

Aged↗
PubMed1990

Preliminary trial of the effect of general practice based nutritional advice.

Despite formal recommendations for dietary change to reduce the incidence of ischaemic heart disease, the acceptability and effectiveness of the proposed diets have not been well investigated in population based studies. In this preliminary investigation of nutritional advice in a well population, subjects in one group practice were randomized to receive either dietary instruction or simple follow up without instruction. The dietary recommendations were well received, and a substantial proportion of subjects reported altering their diets in accordance with them. There were modest beneficial changes in plasma lipid levels among men. Thus, using general practice as an avenue for promoting dietary change is feasible, and may be effective among men.

Adult↗
PubMed1989

Effect of weight loss on coagulation factors VII and X.

Coagulation plays an important role in the pathogenesis of coronary artery disease. Therefore, reversing a tendency to thrombosis may be an avenue for its prevention. Because of an association between obesity and high levels of several coagulation factors, the effect of weight loss on coagulation factors VII and X was investigated among subjects taking part in a 3-month weight loss study. At baseline, both coagulation factors were correlated with age, Quetelet's index, total cholesterol and triglycerides. During the diet period, the subjects lost an average of 3.5 kg at 1 month and 4.2 kg at 3 months, whereas lipoproteins changed in only minor ways. In the group as a whole, factor VII and X both decreased at 1 month but returned to or exceeded the baseline levels despite continued weight loss at 3 months. Although changes in weight, serum total cholesterol and triglycerides were correlated with the changes in the factors during the first month, during months 2 and 3 these correlations remained substantial only for triglycerides. Multiple regression analysis indicated that changes in weight, cholesterol and triglycerides could not explain the decreasing and increasing pattern in factors VII and X. These data suggest that weight itself does not explain the association between obesity and factors VII and X, and that weight loss does not effectively decrease the levels of these factors.

Cholesterol↗
PubMed1989

The Skin Cancer Prevention Study: design of a clinical trial of beta-carotene among persons at high risk for nonmelanoma skin cancer.

We describe a randomized clinical trial of oral beta-carotene (50 mg/day) for preventing nonmelanoma skin cancer. It is a multicenter study conducted at sites in California, Minnesota, and New Hampshire. This report describes the design of the study, baseline characteristics of the 1805 randomized patients, changes in their plasma beta-carotene and retinol levels after 1 year of treatment, and plans for statistical analyses. Important features of this study are (1) a high proportion of potential subjects were found to be ineligible or chose not to enter the study, (2) the study agent is readily available over the counter and in common foods, and (3) nonmelanoma skin cancer is a relatively minor health concern for most patients. These considerations necessitated intensive efforts to encourage compliance with the study regimen. There are also some unusual statistical features of the study. One is that the study outcome is routinely assessed only at annual examinations, so the precise time of failure cannot be identified. Also, a secondary goal of the study is to determine whether beta-carotene decreases the average number of new skin cancers per patient per year, and there are no established statistical methods for analysis of data in this situation. Alternative approaches to the analysis are discussed.

Adult↗
PubMed1989

The clinical utility of risk factor data.

Epidemiological data on risk factors may be used by clinicians to help diagnose the presence of a disease or assess the probability of its developing in the future. However, the use of risk factor data in this way has not been well evaluated. In this report, relationships are derived between common epidemiological measures of association, such as risk ratios, and common clinically useful measures, such as the operating characteristics of tests. These indicate that even a risk factor with a high relative risk may not be effective when used clinically.

Cardiovascular Diseases↗
PubMed1989

Sex hormones and lipoproteins in men.

PURPOSE: To clarify the conflicting evidence of an association between endogenous sex hormones and lipoprotein metabolism in men, we examined the relationship between sex hormone levels, total cholesterol, and high-density lipoprotein cholesterol (HDL-C), taking into account the coronary artery disease (CAD) status of the subjects. PATIENTS AND METHODS: Sex hormone levels, total cholesterol, and HDL-C were measured in 67 men with CAD from among 191 consecutive male patients between the ages of 25 and 75 undergoing coronary angiography, in 26 men without angiographic evidence of CAD, and in 55 men who were clinically free of CAD. RESULTS: There was a consistently positive correlation between total estradiol or calculated free estradiol and both total cholesterol and HDL-C, which persisted after adjustment for potential confounders. Total cholesterol was associated with total testosterone after controlling for age, adiposity, and the presence or absence of CAD, but not with calculated free testosterone. No association was noted between total testosterone or calculated free testosterone and HDL-C. A significant interaction was observed between estradiol and testosterone with respect to total cholesterol. CONCLUSION: This study demonstrates an association between sex hormone levels and lipoprotein metabolism, specifically between estradiol levels and both total cholesterol and HDL-C. Unlike most previous investigators, we were able both to control for the CAD status of our subjects and to consider unbound, biologically active hormone levels. In addition, we documented a complex interaction between endogenous testosterone and estradiol in relation to lipoprotein levels; this association should be considered in future studies.

Adult↗
PubMed1989

Cigarette smoking and breast cancer.

The relation between cigarette smoking and the risk of breast cancer in women was investigated in a population-based case-control study conducted in Adelaide, Australia during 1982-1984. Cases were identified through the South Australian Central Cancer Registry, and, for each case, one age-matched control was selected from the electoral register; in all, 451 case-control pairs were enrolled. Overall, no clear association was found between ever or current smoking and breast cancer risk. In a subgroup analysis, premenopausal ex-smokers were observed to have an increased risk (estimated odds ratio = 2.3). The absence of a protective effect of cigarette smoking on breast cancer risk may reflect the relatively weak estrogen dependence of breast cancer, or the nature of its hormone dependence.

Adult↗
PubMed1989

Determinants of plasma levels of beta-carotene and retinol. Skin Cancer Prevention Study Group.

The associations of retinol and beta-carotene plasma concentrations with eight personal variables and the use of seven classes of cardiovascular drugs were studied in over 1,750 patients with nonmelanoma skin cancer enrolled at four American study centers in a cancer prevention clinical trial. Dietary carotene and female sex were positively related to beta-carotene levels, while cigarette smoking and Quetelet index were negatively related. Use of vitamins, beta blockers, or other antihypertensive drugs were also related to beta-carotene levels, but were associated with much smaller changes in these levels. Age and use of other types of cardiovascular drugs were not associated with beta-carotene levels to a statistically significant extent. There was no statistically significant interaction of smoking and dietary carotene in predicting plasma beta-carotene levels. The multiple correlation coefficient between log plasma beta-carotene and the full model was R = 0.50. Retinol levels were positively related to male sex and use of vitamins, diuretics, beta blockers, other cardiovascular drugs, and menopausal estrogens, and negatively related to current cigarette smoking and use of nitrates. The multiple correlation coefficient between plasma retinol and the full model was R = 0.33. These findings confirm the importance of several previously reported predictors of plasma retinol and beta-carotene levels. They also identify several new predictors of these micronutrient levels.

Adult↗
PubMed1989

Stability of electrophysiological parameters after acute amiodarone loading: implications for patient management.

The appropriate timing of electrophysiological study in patients treated with amiodarone is uncertain. Twenty patients with coronary artery disease in whom sustained ventricular tachycardia was still inducible after 9 +/- 1 days of amiodarone loading (1,200-1,400 mg/day) underwent repeat electrophysiological testing after an additional month of maintenance therapy (400 mg/day). Compared with baseline, both short- and long-term amiodarone therapy caused significant changes in QTc, right ventricular effective refractory period, and ventricular tachycardia cycle length. However, there was no significant change in electrophysiological parameters between the end of the acute amiodarone loading period and 1 month of additional therapy. Sustained ventricular tachycardia remained inducible in 19 of 20 patients after 1 month of maintenance therapy. Amiodarone and desethylamiodarone plasma concentrations remained stable after amiodarone loading, but did not correlate with the magnitude of electrophysiological changes from baseline. These data suggest that electrophysiological testing after 9 days of high dose amiodarone therapy may accurately reflect long-term electrophysiological effects.

Aged↗
PubMed1989

Cigarette smoking and benign proliferative epithelial disorders of the breast in women: a case-control study.

STUDY OBJECTIVE: The purpose of the study was to investigate the possible association between cigarette smoking and benign proliferative epithelial disorders of the breast. DESIGN: This was a case-control study with two different control groups. SETTING: The study was community based and took place in metropolitan Adelaide, South Australia. SUBJECTS: 506 biopsy proven cases between 18 and 75 years were identified, of whom 39 could not be approached because of surgeon refusal, 66 would not be interviewed and 18 were untraceable, leaving 383 for inclusion in the study. Controls were 192 women who had had a negative breast biopsy, out of a possible 259 (17 surgeon refusals, 39 interview refusals, 11 untraceable); and a randomly selected group of women matched to the index group for age and area of residence (582 subjects were approached to enrol 383 controls). MEASUREMENTS AND MAIN RESULTS: All breast biopsies were examined by one pathologist and classified using a standard system. Sociodemographic and medical information was collected by trained interviewers using structured questionnaires. Overall, and within menopausal strata, risk of benign proliferative epithelial disease for women who had ever smoked and for current and ex-smokers was similar to that for women who had never smoked. In premenopausal women, using community controls as the comparison group, risk decreased with cigarette-years of exposure, but the trend was not statistically significant. Risk appeared to increase when biopsy controls were used. There was no trend in the association when examined by degree of cytological atypia. CONCLUSIONS: The data suggest that cigarette smoking is not related to the risk of benign proliferative epithelial breast disease.

Adolescent↗