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Biomedical subjects

J A Baron

Publications and source records attributed to J A Baron.

At least 109 records · Page 6Linked to original sources
PubMed1995

Calcium supplementation and rectal mucosal proliferation: a randomized controlled trial.

BACKGROUND: Data from studies using rodents suggest that dietary calcium inhibits bile acid-induced mucosal damage and experimental carcinogenesis in the large bowel. However, in humans, the effect of dietary calcium and calcium supplementation on proliferation and carcinogenesis in the large bowel has been unclear. PURPOSE: To assess the effect of calcium supplementation on rectal mucosal proliferation in humans, we conducted a multicenter, randomized, placebo-controlled, double-blinded trial. METHODS: Participants were part of a larger multicenter chemoprevention trial; all were at high risk for large-bowel neoplasia, with at least one large-bowel adenoma removed endoscopically within the 3 months before study entry but with no known polyps remaining. Subjects were randomly assigned to receive daily either 3000 mg of calcium carbonate (providing 1200 mg elemental calcium) or an identical-appearing placebo tablet. During a scheduled endoscopy 6-9 months after random assignment (approximately 1 year after the qualifying endoscopy), rectal mucosal samples were obtained from 333 patients (173 assigned to calcium and 160 assigned to placebo). Proliferating cell nuclear antigen (PCNA) labeling indices (LIs) were computed as the measure of proliferation in specimens from 146 patients receiving calcium and 129 patients receiving placebo. Bromodeoxyuridine (BrdU) labeling was used to measure proliferation in a smaller number of specimens (27 calcium-receiving and 31 placebo-receiving participants). For each scorable crypt having at least one labeled cell (or surrounded by crypts with at least one labeled cell), a crypt LI was calculated as the number of labeled cells divided by the total number of crypt cells. Crypt LIs were averaged to produce a participant's average LI. RESULTS: The overall unadjusted mean PCNA LIs (+/- SE) were similar in the calcium and placebo groups (3.85% +/- 0.08% versus 3.92% +/- 0.08%, respectively, P = .30). The overall unadjusted mean BrdU LIs (+/- SE) were 3.88% +/- 0.30% in the calcium group and 3.54% +/- 0.21% in the placebo group (P = .54). PCNA labeling indices in the most luminal 40% of the crypt were small but, if anything, were higher in the calcium group. There was no patient subgroup within which calcium had an antiproliferative effect; the overall findings persisted among patients with high and low calcium intake, high and low fat intake, and high and low fiber intake. CONCLUSIONS: Calcium supplementation does not decrease rectal mucosal proliferation, as measured by PCNA (and BrdU) immunohistochemistry, in patients with previous large-bowel adenomas. This study, therefore, does not provide evidence for an anticarcinogenic effect of calcium.

Adenoma↗
PubMed1995

Use of inferior vena cava filters in the Medicare population.

To examine the use of inferior vena cava (IVC) filters, we performed a population-based study using a 5% random sample of the United States Medicare population (1.25 million persons). Filter placement and its timing relative to diagnosis of venous thromboembolism (VTE) were determined using both hospital and physician Medicare billing codes after detailed review of large samples of complete individual claims records. Comorbid conditions and mortality were also noted. From July 1986 through June 1989, a total of 806 patients in the sample population received IVC filters. Mortality rates after filter placement were high: 16% during initial hospitalization, 32% within 6 months of filter placement, and 48% after 2 years. However, only 3 (1%) of 423 patients who underwent filter placement without the diagnosis of pulmonary embolism (PE) suffered PE within 1 year of filter placement. Use of IVC filters increased significantly over the study period (p < 0.001). Rates of filter placement among the nine census divisions of the United States differed significantly (p < 0.001). An East-West trend was notable with the highest rate (37 filters/100,000 enrollees/yr) in New England, as compared with 14 filters/100,000 enrollees/yr in the Pacific Division. No explanation for these regional differences was evident after patient demographics and comorbidity were examined. Vena cava filters prevent PE for at least 1 year after placement. The frequency of IVC filter use in elderly patients is increasing and varies substantially by region. Although reasons for these trends are unclear, these findings suggest the need for uniform practice guidelines for IVC filter placement.

Aged↗
PubMed1995

The short-term effect of nicotine chewing gum in patients with Parkinson's disease.

Because of the inverse association of cigarette smoking with the risk of Parkinson's disease, we performed a short-term, double-blind, randomized controlled trial of nicotine polacrilex resin gum in patients with this disease. Forty-eight subjects were randomly assigned to chew either nicotine gum or placebo gum three times at 2-h intervals, with evaluation of symptoms before and after the trial. The nicotine gum was reasonably well tolerated, but there were no substantial differences in Parkinson's disease symptoms between the two treatment groups.

Aged↗
PubMed1995

Number of siblings and subsequent gastric cancer risk.

The number of siblings is an indirect indicator of living and, possibly, dietary conditions in childhood and adolescence. The relationship between the number of siblings and subsequent gastric cancer risk was analysed using data from a case--control study conducted in Italy between 1985 and 1992 on 723 cases of incident, histologically confirmed gastric cancer and 2,024 controls in hospital for acute, non-neoplastic, non-digestive tract disorders. After allowance for age and sex, there was a significant trend of increasing gastric cancer risk with increasing number of siblings (P < 0.01). Compared with subjects with no siblings, the relative risk (RR) was 1.1 for those with one, 1.3 for 2, 1.4 for 3-6 and 1.7 for 7 or more siblings. The association was stronger in subjects above the age of 60: the RR for > or = 5 siblings was 1.8, as compared with 1.2 for younger subjects. These patterns of trends are consistent with the hypothesis that domestic crowding and deprivation in childhood and adolescence is a correlate of subsequent gastric cancer risk, and offer therefore interesting clues to our understanding of the process of gastric carcinogenesis.

Adolescent↗
PubMed1995

The effect of cigarette smoking on adrenal cortical hormones.

We assessed the association between cigarette smoking and basal levels of adrenal cortical hormones in 11 postmenopausal smokers and 11 postmenopausal nonsmokers and measured the acute adrenal effects of cigarettes in the smokers. After an overnight food, alcohol and tobacco fast, participants smoked or sham-smoked every hr for 8 hr and provided serum samples for hormone assay before and after every other cigarette/sham, as well as before and after a corticotropin stimulation test. The postmenopausal smokers had substantially higher basal levels of androstenedione (4.60 +/- 0.42 vs. 2.70 +/- 0.36 nmol/l, P < .05) and dihydroepiandrosterone sulfate (2.88 +/- 0.36 vs. 1.91 +/- 0.16 mumol/l, P < .05) and higher average levels of cortisol and androstenedione from 0800 to 1300 hr (351.0 +/- 17.5 vs. 295.5 +/- 17.1, nmol/l and 3.58 +/- 0.42 vs. 2.51 +/- 0.19 nmol/l, P = .03, and P < .05, respectively). There were small acute effects of individual cigarettes on the hormones, but the response to corticotropin was similar in smokers and nonsmokers. Our results indicate that cigarette smoking causes a generalized disturbance in adrenal cortical hormone levels. There is no evidence for acute tolerance to the adrenocortical affects of the hourly smoking of medium-nicotine cigarettes, but these acute effects do not explain the higher hormone levels in smokers. There is no evidence for a partial block in the cortisol synthesis pathway to explain the increased adrenal androgen levels in smokers.

Adrenal Cortex↗
PubMed1995

Alcohol intake and breast cancer risk: effect of exposure from 15 years of age.

Research regarding the relationship between alcohol intake and breast cancer risk has suggested an association between the two, although the data are inconsistent regarding dose effects and susceptible populations. To clarify these issues, we investigated the association of breast cancer risk with alcohol intake at various ages in a population-based case-control study nested within a screening cohort in Sweden. Subjects were women 40-75 years old who participated in a screening program in central Sweden. Information about personal characteristics, diet, and alcohol intake was obtained by a questionnaire sent out at the invitation to the screening interview and at a supplementary interview conducted among a sample of women who did and did not develop breast cancer. Alcohol intake did not affect breast cancer risk among women under 50 years old. However, among those over 50 years of age, ever-drinking conferred a relative risk of 1.8 (95% confidence interval = 1.2-2.6). Current and former drinkers had similar increases in risk. No particular latent period of alcohol effect was identified, but drinking later in life to have a bigger effect than did drinking earlier in life.

Adolescent↗
PubMed1994

A clinical trial of antioxidant vitamins to prevent colorectal adenoma. Polyp Prevention Study Group.

BACKGROUND: People who consume a diet high in vegetables and fruits have a lower risk of cancer of the large bowel. Antioxidant vitamins, which are present in vegetables and fruits, have been associated with a diminished risk of cancers at various anatomical sites. We conducted a randomized, controlled clinical trial to test the efficacy of beta carotene and vitamins C and E in preventing colorectal adenoma, a precursor of invasive cancer. METHODS: We randomly assigned 864 patients, using a two-by-two factorial design, to four treatment groups, which received placebo; beta carotene (25 mg daily); vitamin C (1 g daily) and vitamin E (400 mg daily); or the beta carotene plus vitamins C and E. In order to identify new adenomas, we performed complete colonoscopic examinations in the patients one year and four years after they entered the study. The primary end points for analyses were new adenomas identified after the first of these two follow-up examinations. RESULTS: Patients adhered well to the prescribed regimen, and 751 completed the four-year clinical trial. There was no evidence that either beta carotene or vitamins C and E reduced the incidence of adenomas; the relative risk for beta carotene was 1.01 (95 percent confidence interval, 0.85 to 1.20); for vitamins C and E, it was 1.08 (95 percent confidence interval, 0.91 to 1.29). Neither treatment appeared to be effective in any subgroup of patients or in the prevention of any subtype of polyp defined by size or location. CONCLUSIONS: The lack of efficacy of these vitamins argues against the use of supplemental beta carotene and vitamins C and E to prevent colorectal cancer. Although our data do not prove definitively that these antioxidants have no anticancer effect, other dietary factors may make more important contributions to the reduction in the risk of cancer associated with a diet high in vegetables and fruits.

Adenomatous Polyps↗
PubMed1994

The epidemiology of diagnosed pulmonary embolism and deep venous thrombosis in the elderly.

BACKGROUND: There are no studies that define the basic epidemiology of pulmonary embolism (PE) and deep venous thrombosis (DVT) in the elderly. This project was undertaken to provide that information. METHODS: We obtained all Medicare claims during the period 1986 through 1989 from a random 5% sample of US Medicare enrollees. By selecting codes used for diagnoses and treatment, we identified 7174 cases of PE and 8923 cases of DVT. These cohorts were analyzed to provide incidence by age, race, sex, and geographic location; frequency of invasive treatment; frequency of PE after treatment for DVT; frequency of recurrence of PE; and survival after diagnosis. RESULTS: Annual incidence rates per 1000 at age 65 to 69 years for PE and DVT were 1.3 and 1.8, respectively. Both rates increased steadily with age to 2.8 and 3.1 by age 85 to 89 years. For PE, women had lower rates than men (adjusted relative risk, 0.86; 95% confidence interval, 0.82 to 0.90), and blacks had higher rates than whites (adjusted relative risk, 1.25; 95% confidence interval, 1.15 to 1.36). For DVT, the associations with gender and race were weaker and in the opposite direction. Pulmonary embolectomy was done in 0.2% of cases of PE; interruption of the vena cava was done in 4.4% of cases of PE and in 2% of cases of DVT. Thrombectomy was done in 0.3% of all cases. Pulmonary embolism occurred in 1.7% of patients with DVT within 1 year of hospital discharge for initial treatment. The 1-year recurrence rate for PE was 8.0%. In-hospital mortality associated with PE and DVT was 21% and 3%, respectively. One-year mortality was 39% and 21%, respectively. CONCLUSIONS: Pulmonary embolism and DVT are common problems in the elderly. Both increase with age, but the effects of race and sex are small. Current treatment patterns appear to be effective in preventing both PE after DVT and recurrence of PE. Both are associated with substantial 1-year mortality, suggesting the need to understand the role of associated conditions as well as the indications for prophylaxis and the methods of treatment.

Black or African American↗
PubMed1994

Racial differences in fracture risk.

Blacks appear to have a lower risk of fractures than whites, but there has been little research regarding racial differences in the risk of fractures at sites other than the hip. We used Medicare claims to investigate the risks of fractures of the hip, distal forearm, proximal humerus, and ankle among American whites and blacks over 65 years old. Each of these fractures occurred more frequently in women than in men and (except for ankle fracture) displayed an increase in risk with age. Blacks had a lower risk than whites, although these differences were smaller for fractures of the ankle and were less pronounced among men. The most likely explanation for this is a constitutional or metabolic factor prevalent in blacks that particularly influences the risk of osteoporotic fractures in women.

Aged↗
PubMed1994

A two-stage validation study for determining sensitivity and specificity.

A two-stage procedure for estimating sensitivity and specificity is described. The procedure is developed in the context of a validation study for self-reported atypical nevi, a potentially useful measure in the study of risk factors for malignant melanoma. The first stage consists of a sample of N individuals classified only by the test measure. The second stage is a subsample of size m, stratified according the information collected in the first stage, in which the presence of atypical nevi is determined by clinical examination. Using missing data methods for contingency tables, maximum likelihood estimators for the joint distribution of the test measure and the "gold standard" clinical evaluation are presented, along with efficient estimators for the sensitivity and specificity. Asymptotic coefficients of variation are computed to compare alternative sampling strategies for the second stage.

Adult↗
PubMed1994

Treatment and survival among elderly Americans with hip fractures: a population-based study.

OBJECTIVES: This study was undertaken to examine the patterns of treatment and survival among elderly Americans with hip fracture. METHODS: A 5% national sample of Medicare claims was used to identify patients who sustained hip fractures between 1986 and 1989. In comparing treatment patterns across regions, direct standardization was used to derive age- and race-adjusted percentages. Logistic regression and Cox regression were used to examine short- and long-term survival. RESULTS: In the United States, 64% of femoral neck fractures were treated with arthroplasty; 90% of pertrochanteric fractures were treated with internal fixation. Higher short- and long-term mortality was associated with being male, being older, residing in a nursing home prior to fracture, having a higher comorbidity score, and having a pertrochanteric fracture. Blacks and Whites had similar 90-day postfracture mortality, but Blacks had a higher mortality later on. For femoral neck fracture, internal fixation has a modestly lower short-term mortality associated with it than arthroplasty has. CONCLUSION: Variation in the treatment of hip fracture was modest, The increased delayed mortality after hip fracture among Blacks requires further study.

Age Factors↗
PubMed1994

Internal validation of Medicare claims data.

The Medicare database is commonly used for epidemiology and health services research, but validation of its data by chart review or questionnaire may be difficult and expensive. Since hospital and physician bills are independent in Medicare, however, these two data sources can be used to supplement and corroborate each other. This "internal validation" is illustrated here for hip fracture and prostatectomy. Agreement of the hospital and physician data streams regarding site of hip fracture (neck vs other), treatment of hip fracture (internal fixation vs arthroplasty), and type of prostatectomy (transurethral resection of prostate, open, or radical) was excellent, with percentage of agreement generally between 89% and 99%, and kappa statistics typically between 0.74 and 0.95. When validation with outside data sources is not readily available, such internal validation of Medicare data may be valuable.

Abstracting and Indexing↗