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Biomedical subjects

J A Baron

Publications and source records attributed to J A Baron.

At least 91 records · Page 5Linked to original sources
PubMed1996

History of childbearing and colorectal cancer risk in women aged less than 60: an analysis of Swedish routine registry data 1960-1984.

Data from a computerised linkage between the Swedish Cancer Registry and the Fertility Registry were used to study the influence of reproductive history on the risk of colorectal cancer in women aged less than 60, in the period 1960 to 1984. A "nested" case-control design was used with 1,415 colon cancer cases and 733 rectal cancer cases, and 7,073 and 3,665 age-matched controls, respectively. Conditional logistic regression was employed to study the independent effects of parity, age at first birth and years since last birth on the risk of colorectal cancer. High parity was associated with reduced risk in women older then 50 years at diagnosis, both for the colon as a whole and for colon subsites. Women having had 5 children or more had an odds of colon cancer of 0.44 (95% confidence interval 0.24-0.82) relative to that of nulliparous woman. Contrary to the hypothesis advanced by McMichael and Potter (J. Nat. Cancer Inst., 75, 185-191 [1985]), which predicted a strong protective effect of parity in the proximal compared to the distal colon, we found the reverse. Increasing years since last birth seemed to be associated with a reduced risk of rectal cancer. A significant positive trend with increasing age at first birth was suggested with respect to distal colon cancer and rectal cancer risk. The mutually adjusted effects of the reproductive variables under study were similar to the unadjusted effects. Our data suggest that increasing parity is associated with a decline in risk of colon cancer but not rectal cancer, although the association with colon cancer is restricted to women aged 50 or more. The effects of age at first birth and years since last birth are not consistent or pronounced.

Adult↗
PubMed1996

Heterogeneity of hip fracture: age, race, sex, and geographic patterns of femoral neck and trochanteric fractures among the US elderly.

To explore potential etiologic differences in the two major types of hip fracture, the authors computed the incidence rates of fractures of the femoral neck and trochanteric region of the proximal femur using a 5 percent sample of the US Medicare population aged 65-99 years. For the period they examined, July 1, 1986, through June 30, 1990, the rates of both hip fracture types increased with age in all race and sex categories. The proportion of hip fractures that occurred in the trochanteric region rose steeply with age among white women, but not among black women, white men, or black men. Within the United States, a north-to-south gradient in rates of both fracture types was observed among women, while no clear pattern was found for men. These findings raise the possibility of etiologic differences in the two fracture types, and the results provide further evidence of sex and racial differences in the risk of osteoporotic fractures.

Black or African American↗
PubMed1996

Mortality associated with low plasma concentration of beta carotene and the effect of oral supplementation.

OBJECTIVE: To examine the relationship between beta carotene plasma concentration and beta carotene supplementation and risk of death from major disease causes. DESIGN: Cohort study of plasma concentrations; randomized, controlled clinical trial of supplementation. SETTING: Medical school-affiliated dermatology practices. PATIENTS: A total of 1188 men and 532 women with mean age of 63.2 years, who had enrolled in a randomized clinical trial of beta carotene supplementation to prevent nonmelanoma skin cancer. INTERVENTION: Oral beta carotene, 50 mg per day for a median of 4.3 years. MAIN OUTCOME MEASURES: All-cause mortality and mortality from cardiovascular disease and cancer. RESULTS: During a median follow-up period of 8.2 years, there were 285 deaths. Persons whose initial plasma beta carotene concentrations were in the highest quartile (>0.52 micromol/L [27.7 microg/dL]) had a lower risk of death from all causes (adjusted relative rate [RR], 0.52; 95% confidence interval [CI] 0.44 to 0.87) and from cardiovascular diseases (adjusted RR, 0.57; 95% CI, 0.34 to 0.95) compared with persons with initial concentrations in the lowest quartile (<0.21 micromol/L [11.2 microg/dL]). Patients randomly assigned to beta carotene supplementation showed no reduction in relative mortality rates from all causes (adjusted RR, 1.03; 95% CI, 0.82 to 1.30) or from cardiovascular disease (adjusted RR, 1.16; 95% CI, 0.82 to 1.64). There was no evidence of lower mortality following supplementation among patients with initial beta carotene concentrations below the median for the study group. CONCLUSIONS: These analyses provide no support for a strong effect of supplemental beta carotene in reducing mortality from cardiovascular disease or other causes. Although the possibility exists that beta carotene supplementation produces benefits that are too small or too delayed to have been detected in this study, noncausal explanations should be sought for the association between plasma concentrations of beta carotene and diminished risk of death.

Administration, Oral↗
PubMed1996

Variation in female breast cancer risk by occupation.

Data from a population-based case control study were used to estimate occupation-specific relative risks for female breast cancer, adjusted for established breast cancer risk factors. Breast cancer cases under age 75 were identified from tumor registries in four states. Controls were randomly selected from driver's license and Medicare beneficiary lists. Information on usual occupation and risk factors was obtained by telephone interview. Odds ratios from logistic regression adjusted for age, state, body mass index, benign breast disease, family history of breast cancer, menopausal status, age at menarche, parity, age of first birth, lactation history, education, and alcohol consumption were calculated for each of 26 occupational groups. Complete occupational information was obtained for 6,835 cases and 9,453 controls. Of 26 occupational groups, only "administrative support occupations" had a statistically significantly increased risk of breast cancer (OR = 1.15, 95% CI 1.06-1.24). In these data, no specific occupational group had an unusual risk of breast cancer. Increased risks reported elsewhere for nurses and teachers were not corroborated.

Administrative Personnel↗
PubMed1996

The effect of smoking at different life stages on bone mineral density in elderly men and women.

To assess the effect of smoking on bone mineral density (BMD) at different life stages, to examine whether the effect of smoking differs between men and women, and to discover whether its effect in women differs according to history of estrogen use, a cohort study was carried out with single cross-section measurement of BMD by single and dual photon absorptiometry. The setting was the Framingham Study, a population-based cohort study with over 40 years prospectively collected data on smoking. Subjects (n = 1164) consisted of cohort members participating in the 20th biennial Framingham examination (1988-1989). The measurements included in the study were BMD measured at the hip, spine and radius, smoking history ascertained at all Framingham Study examinations since 1948, and other factors affecting BMD (age, weight, estrogen use, caffeine use, alcohol use and physical activity). Neither current smoking, recent (last 10 years) smoking, nor early adulthood smoking resulted in significantly lower BMD at any skeletal site among women who had not taken estrogen. Among women who had taken estrogen, BMD at most sites was lower among current or recent smokers, although the small numbers of smokers made it difficult to find significant differences at all skeletal sites. Among men, a consistently lower BMD at all skeletal sites was observed for smokers regardless of when in their life they smoked (4-15.3% lower), although the effect of smoking during early adulthood was of a lesser magnitude (4-8% lower). Former male smokers who had quit < 10 years ago had lower BMD than men who had quit > or = 10 years ago. In conclusion, in women who had used estrogen, BMD was lower in current or recent smokers than it was in non-smokers. In men, smoking at any stage of life had adverse effects on the skeleton that was independent of weight, alcohol or caffeine use, implying other mechanisms for smoking's effect on bone.

Absorptiometry, Photon↗
PubMed1996

Patterns of fracture among the United States elderly: geographic and fluoride effects.

The purpose of this study was to examine whether geographic area or water fluoride were related to the occurrence of fractures among the elderly in the United States. We used a 5% sample of the white U.S. Medicare population, aged 65 to 89 years during the period 1986-1990, to identify fractures of the hip, proximal humerus, distal forearm, and ankle. The association of geographic region and fluoridation status with fracture rates was assessed using Poisson regression. We found that rates of hip fracture were generally lower in the northern regions of the United States and higher in the southern regions. For fractures of the distal forearm and proximal humerus, lower rates were found in the Western states, and higher rates in the East. No discernible geographic pattern was found for ankle fractures. Adjustment for water fluoridation did not influence these results. Independent of geographic effects, men in fluoridated areas had modestly higher rates of fractures of the distal forearm and proximal humerus than did men in nonfluoridated areas; no such differences were observed among women, nor for fractures of the hip or ankle among either men or women. In conclusion, our data suggest that fractures of the distal forearm and proximal humerus have etiologic determinants distinct from those of fractures of the hip or ankle.

Aged↗
PubMed1996

The epidemiology of peripheral fractures.

Although much is known about hip fracture epidemiology, there are relatively little data regarding fractures at other peripheral sites. Epidemiological differences between fractures are important, since they imply that an understanding of the consequences and clinical expression of osteoporosis requires the study of many different fracture types. Recent data regarding the basic epidemiology of limb fractures among the elderly in industrialized countries have made some patterns clear. Fractures outside the hip are relatively common events, and before age 70 to 75, ankle and distal forearm fractures occur more commonly than fractures of the hip. Among the elderly, fractures at the most proximal and most distal ends of the limbs have the highest incidence. Thus, in the upper extremity, fractures of the proximal humerus and distal forearm are the most common, while in the lower extremity, those at the hip and ankle predominate. Outside the axial skeleton, females have higher rates for most fracture types, and at most fracture sites whites have higher rates than blacks. In each limb, the most proximal fractures tend to have the most pronounced age-related increases in risk.

Aged↗
PubMed1996

Beneficial effects of nicotine and cigarette smoking: the real, the possible and the spurious.

Cigarette smoking is an established risk factor for cancer and cardiovascular disease, and is the leading cause of avoidable disease in most industrialized countries. Less well-known are possible beneficial effects, which are briefly considered in this survey. Preliminary data suggest that there may be inverse associations of smoking with uterine fibroids and endometriosis, and protective effects on hypertensive disorders and vomiting of pregnancy are likely. Smoking has consistently been found to be inversely related to the risk of endometrial cancer, but cancers of the breast and colon seem unrelated to smoking. Inverse associations with venous thrombosis and fatality after myocardial infarction are probably not causal, but indications of benefits with regard to recurrent aphthous ulcers, ulcerative colitis, and control of body weight may well reflect a genuine benefit. Evidence is growing that cigarette smoking and nicotine may prevent or ameliorate Parkinson's disease, and could do so in Alzheimer's dementia. A variety of mechanisms for potentially beneficial effects of smoking have been proposed, but three predominate: the 'anti-estrogenic effect' of smoking; alterations in prostaglandin production; and stimulation of nicotinic cholinergic receptors in the central nervous system. Even established inverse associations cannot be used as a rationale for cigarette smoking. These data can be used, however, to clarify mechanisms of disease, and point to productive treatment or preventive options with more narrowly-acting interventions.

Alveolitis, Extrinsic Allergic↗
PubMed1996

Basic epidemiology of fractures of the upper and lower limb among Americans over 65 years of age.

Current knowledge regarding the basic epidemiology of fractures is largely limited to a few fracture sites, notably those of the hip and distal forearm. To clarify the patterns of incidence of limb fractures in the elderly, we used data from a 5% sample of the U.S. Medicare population over age 65 years during the years 1986-1990. We identified incident fractures of the proximal humerus, other parts of the humerus, proximal radius/ ulna, shaft of the radius/ulna, distal radius/ulna, pelvis, hip, other parts of the femur, patella, ankle, and other parts of the tibia/fibula from diagnoses and procedures coded on claims for inpatient services, outpatient facility use, and physician services. We used Poisson regression to investigate the relation between demographic factors and fracture risk at these sites. Fractures at the hip were the most common, accounting for 38% of the fractures identified. The proximal humerus, distal radius/ulna, and ankle also were common fracture sites. A pattern of rapidly rising rates with age was seen for fractures of the pelvis, hip, and other parts of the femur among women. Fractures distal to the elbow or knee, however, had, at most, modest increases in incidence with age over 65 years. For each of the fractures studied, women had higher rates than men of the same race, and whites generally had higher rates than blacks of the same gender. Gender-related differences in risk were larger among whites than among blacks, and racial differences in risk were more marked among women than among men.

Aged↗
PubMed1996

The accuracy of skin self-examination for atypical nevi.

We conducted a validation study to assess laypersons' ability to self-report atypical nevi. Study subjects were drawn from a large population-based cohort of middle-aged Swedish women who had responded to a previous health survey. The health survey questionnaire included color photographs of atypical nevi. Respondents were asked to examine their lower extremities for similar lesions. We invited 500 survey respondents to participate in a physician-conducted skin examination; 400 (80%) subjects agreed. We compared the results of skin self-examination for atypical nevi to the results of the physician-conducted skin examination. Using methods developed for this study, we estimated sensitivity as 29% and specificity as 85%. Positive predictive value was 20%; negative predictive value was 90%. We estimated that 12% of Swedish women have atypical nevi on the lower extremities. Although these findings suggest poor accuracy of skin self-examination for atypical nevi, our results may have been adversely affected by limiting self-examination to the legs and by the severity of atypical nevi shown in the comparison photographs used by survey respondents.

Adult↗
PubMed1996

Total hip arthroplasty: use and select complications in the US Medicare population.

Use and outcomes of primary total hip arthroplasty among US Medicare recipients more than 65 years of age were investigated by means of physician and hospital claims for a 5% random sample during 1986 through 1989. Cases involving hip fracture or evidence of existing orthopedic devices in the hip were omitted. Use rates were higher for women than for men and were substantially lower for Blacks than Whites. Major complications (death, further hip surgery, infection pulmonary embolism) were uncommon. These data document the frequent use of total hip arthroplasty, and confirm the rarity of serious adverse outcomes. Further studies should investigate the lower use of total hip arthroplasty among Blacks.

Black or African American↗
PubMed1996

Reproductive history and cigarette smoking as risk factors for thyroid cancer in women: a population-based case-control study.

A population-based case-control study was conducted in Northern Norway and Central Sweden to investigate hormonal and reproductive factors and cigarette smoking as determinants of papillary and follicular thyroid carcinoma in women. Information on 191 histologically confirmed cases and 341 age-matched controls was included. No clear association was found with regard to the number of live births, number of pregnancies, a history of incomplete pregnancies, or the use of oral contraceptives or hormonal replacement therapy. However, an early first childbirth (before 20 years of age, or less than 5 years after menarche) was associated with an increased risk of thyroid cancer. There was an increased risk of thyroid cancer among women with a history of artificial menopause compared to those with a spontaneous menopause [odds ratio (OR), 2.52; 95% confidence interval (CI), 0.96-6.62], which was more pronounced for the papillary carcinoma and after adjustment for age at menopause and use of replacement therapy. Cigarette smokers had a decreased risk of borderline statistical significance compared to nonsmokers (OR, 0.69; 95% CI, 0.47-1.01), particularly among premenopausal women (OR, 0.60; 95% CI, 0.38-0.96). This negative association persisted after adjustment for parity, hormonal treatments, and education. Women who started smoking before the age of 15 experienced a marked reduction in risk (OR, 0.38%; 95% CI, 0.18-0.80¿). Moreover, there was a suggestion of a dose-response effect with the amount of cigarettes smoked daily and with duration of the habit. Both the increased risk of artificial menopause and the negative association with smoking are compatible with a relation between levels of estrogens and thyroid cancer among women.

Adenocarcinoma, Follicular↗
PubMed1996

Occupational exposure to 60-hertz magnetic fields and risk of breast cancer in women.

We used data from a large population-based case-control study to test the hypothesis that women whose "usual occupation" entailed exposure to higher than background 60-Hz magnetic fields had a higher risk of breast cancer than women without such exposure. Breast cancer cases were identified from four statewide tumor registries, and controls were randomly selected from lists of licensed drivers and Medicare beneficiaries. Information on usual occupation and breast cancer risk factors was obtained by telephone interview. We calculated adjusted odds ratios from logistic regression models for women holding occupations with potential for low, medium, or high magnetic field exposure, compared with background exposure. There was a modest increase in risk for women with potential for high exposure [odds ratio (OR) = 1.43; 95% confidence interval (CI) = 0.99-2.09], and no increase for women with potential for medium (OR = 1.09; 95% CI = 0.83-1.42) or low (OR = 1.02; 95% CI = 0.91-1.15) exposure The risk among premenopausal women in the highest-exposure category was higher (OR = 1.98; 95% CI = 1.04-3.78) than for postmenopausal women (OR = 1.33; 95% CI = 0.82-2.17).

Breast Neoplasms↗
PubMed1996

Dietary calcium, vitamin D, and the risk of colorectal cancer in Stockholm, Sweden.

The epidemiology of large bowel cancer suggests an etiological role for dietary factors. Although the evidence is inconsistent, several studies have suggested an inverse association between dietary vitamin D or calcium and colorectal cancer risk. We conducted a population-based case-control study to examine the relationship between dietary vitamin D and calcium and colorectal cancer among residents of Stockholm, Sweden. Between January 1986 and March 1988, 352 cases of colon cancer and 217 cases of rectal cancer diagnosed among living persons residing in Stockholm County were identified via a cancer surveillance network established among all the hospitals in Sweden and the Stockholm Regional Cancer Registry. Controls (512) were randomly selected from a computerized population registry. Dietary intake was assessed using a quantitative food frequency questionnaire focusing on average consumption during the preceding 5 years. Supplemental intake of vitamin D and calcium was not ascertained. Logistic regression was used to calculate odds ratios (ORs) as the measure of association between the exposure of interest (vitamin D or calcium) and cancer risk. Increasing levels of dietary vitamin D were inversely associated with the risk of colorectal cancer. The association was somewhat more pronounced for cancers of the rectum [OR, 0.5; 95% confidence interval (CI), 0.3-0.9 between the highest and lowest quartiles] than for cancers of the colon (OR, 0.6; 95% CI, 0.4-1.0) after adjustment for age, sex, and total caloric and protein intake. Dietary calcium was not associated with the adjusted risk of colon (OR, 1.2; 95% CI, 0.7-2.1) or rectal cancer (OR, 1.0; 95% CI, 0.5-1.9). Further adjustments for fat and dietary fiber intake, body mass index, and physical activity had little or no effect on the results. These results suggest that dietary vitamin D may reduce the risk of large bowel cancer, particularly rectal cancer. In addition, although some of the previous data suggested a protective effect for calcium against cancers of the large bowel, we could not document such an effect.

Aged↗
PubMed1996

Aspirin and other nonsteroid anti-inflammatory drugs as cancer-preventive agents.

Several lines of evidence support the notion that aspirin and other nonsteroid anti-inflammatory drugs (NSAIDs) may prevent human cancer, particularly cancers of the large bowel. These drugs are potent inhibitors of cyclo-oxygenases, enzymes that catalyse the synthesis of prostaglandins from arachidonic acid. In rodent models, NSAIDs consistently inhibit chemically induced neoplasms of the colorectum. Case reports and randomized controlled trials are also consistent in showing a reduction in adenomas following administration of the NSAID sulindac to patients with familial adenomatous polyposis. Perhaps the most intriguing evidence, however, comes from epidemiological studies, which indicate a 30-50% reduction in risk of colorectal neoplasia among regular users of aspirin. These studies have employed both case-control and cohort approaches, and lower risk has been found for colon and rectal cancer mortality, invasive cancer incidence, and adenoma occurrence. The results of the epidemiological studies are not uniform, however, and a few studies found no benefit with aspirin use. Existing epidemiological studies are limited by a lack of information about dosage and duration of aspirin use. Moreover, questions remain about the mechanism through which NSAIDs might affect cancer occurrence. Thus, there is a clear need for focused clinical trials, as well as for further epidemiological study and laboratory investigation, to define better the potential of these agents to prevent cancers.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1996

Large bowel adenomas: markers of risk and endpoints.

In many large bowel chemoprevention trials adenomas have a double duty: they are used to identify subjects at risk for large bowel neoplasia, and also serve as endpoints. Many features of adenomas make them suitable for these tasks. Patients with adenomas are fairly numerous and easy to identify; further, the 'adenoma-carcinoma' sequence suggests that adenomas are logical endpoints. The high recurrence risk among adenoma patients means that a relatively modest number of subjects will suffice for adequate statistical power. The are some limitations to the use of adenomas, however. There is clearly heterogeneity of risk for subsequent cancer. Patients with only small adenomas may have rates of colorectal cancer that are not much greater than those of the general population. Certainly subjects with large adenomas, and those with villous or highly dysplastic adenomas have a higher risk. Often, one would chose the high-risk patients for preventive interventions. Such a strategy makes sense from a risk-benefit point of view. However, from a population perspective, such a strategy may well have only a minor impact on the overall colorectal cancer burden. For more complete population-based prevention, efforts will have to be directed to the numerous individuals who are each at small risk, but who collectively account for most colorectal cancer. For this preventive approach, patients with any adenoma would certainly be part of the target population, and so are sensible subjects in chemoprevention trials. There are similar complexities in consideration of the use of adenomas as endpoints of chemoprevention trials. The adenomas that occur in prevention trials are generally small, and may not be associated with a greatly increased cancer risk. The issue for chemoprevention trials however, is not whether the endpoints are truly intermediate in the causal chain-but whether the intervention under study alters the adenoma recurrence risk to the same extent as it does for colorectal cancer risk. This is a difficult matter to verify, but the limited data available are encouraging. The epidemiology of colorectal adenomas (largely small adenomas) is similar in many regards to that for colorectal cancer itself. Thus to the extent that data are available, one can tentatively conclude that external influences affect adenomas and colorectal cancer similarly. To date, more than ten adenoma prevention trials have reported results. The data have been fairly consistent. Vitamin C (with or without vitamin E) has provided at most a modest protective benefit, except in one small trial in which it was combined with vitamin E and preformed vitamin A. beta-Carotene seems to be without any effect, and interventions to increase fiber and decrease fat intake have not indicated substantial effects. On the other hand, trials among familial polyposis patients have provided evidence for an impact of nonsteroidal anti-inflammatory drugs. Studies in progress have the potential to clarify greatly the preventive potential of the currently promising-but yet unproven-chemopreventive regimens.

Adenoma↗
PubMed1996

Cigarette smoking and breast cancer.

A priori hypotheses suggest that cigarette smoking could either increase or decrease breast cancer incidence. To clarify these competing hypotheses, we used data from a very large population-based breast cancer case-control study to investigate the impact of smoking on breast cancer risk. Breast cancer patients less than 75 years old were identified from statewide tumor registries in Wisconsin, Massachusetts, Maine, and New Hampshire; controls were randomly selected from driver's license lists (age less than 65) or lists of Medicare beneficiaries (age 65-74). Information on reproductive history, medical history, and personal habits including cigarette smoking was obtained by telephone interview. A total of 6,888 cases and 9,529 controls were interviewed. There was virtually no relationship between current smoking and breast cancer risk (multivariate odds ratio, 1.00; 95% confidence interval, 0.92-1.09), and former smokers had a barely increased risk (odds ratio, 1.10; 95% confidence interval, 1.01-1.19). Similar results were observed among both premenopausal and postmenopausal women. There was no suggestion that heavy or long-term smoking increased or decreased risk, nor were there indications that women who began smoking at an early age were at increased risk, as has been hypothesized. The results of this large population-based study indicate that smoking does not influence the risk of breast cancer, even among heavy smokers who began smoking at an early age.

Age Factors↗