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H Brenner

Publications and source records attributed to H Brenner.

At least 199 records · Page 11Linked to original sources
PubMed1993

Use of the positive predictive value to correct for disease misclassification in epidemiologic studies.

Misclassification problems of the disease status often arise in large epidemiologic cohort studies in which the outcome is classified on the basis of record linkage with routinely collected error-prone data sources, such as cancer registries or mortality statistics. If the misclassification is nondifferential, i.e., independent of the exposure status, this leads to bias toward the null in estimates of relative risk. A variety of methods have been proposed to correct for this bias. Most approaches are based on estimates of the sensitivity and specificity of disease classification from validation studies, which typically require invasive and time-consuming diagnostic procedures. For ethical and practical reasons, such procedures may often not be applied on individuals classified as not having the disease, in which case estimates of sensitivity and specificity cannot be obtained. In this paper, an alternative correction method is proposed based on estimates of the positive predictive value, which requires validation of the diagnosis among samples of individuals classified as having the disease only. The method is applicable in situations with either differential or nondifferential specificity of disease classification as long as the sensitivity is nondifferential. Point estimates and large-sample interval estimates of the corrected relative risk are algebraically derived. The performance of the method is assessed by extensive simulations and found to be satisfactory even for small sample sizes.

Bias↗
PubMed1993

Misclassification bias arising from random error in exposure measurement: implications for dual measurement strategies.

Despite the resulting loss of information, continuous exposure variables are often categorized in epidemiologic data analysis. It has been shown that nondifferential measurement error of exposure can lead to differential misclassification under these circumstances. This paper extends these findings to the misclassification bias that results from nondifferential measurement error if dual measurement strategies are employed with dichotomized exposures. Different scenarios of random measurement error are presented in the context of case-control studies. Although differences in the misclassification rates between cases and controls are generally small, the bias toward the null is usually much weaker than expected under truly nondifferential exposure misclassification even with single exposure measurements. In most cases, the bias is further reduced by the use of dual measurements. Caution is needed, however, if the analysis is restricted to individuals with concordant exposure classifications (both measurements above or both measurements below the cutpoint). In this case, the true exposure-disease association is often overestimated.

Bias↗
PubMed1993

V delta 2+ gamma delta T lymphocytes are cytotoxic to the MCF 7 breast carcinoma cell line and can be detected among the T cells that infiltrate breast tumors.

In order to study the potential role of gamma delta T lymphocytes in cytotoxicity against breast carcinoma cells, normal peripheral blood gamma delta cells were isolated and triggered with an alloantigenic lymphoblastoid B cell line and recombinant interleukin-2 and cloned. The clones expressed a CD3+V gamma 9+V delta 2+CD4-CD8- (or CD8+) phenotype. Five clones were cytotoxic to the Molt 4 T cell leukemia, but not to the alloantigen, whereas one clone lysed the alloantigen, but not the Molt 4 line. Clones that were cytotoxic to Molt 4 were either spontaneously cytotoxic against MCF 7 breast carcinoma cells or could be induced to kill MCF 7 cells by monoclonal antibodies specific for the gamma delta T cell receptor. In situ staining demonstrated that V delta 2+ as well as other subsets of gamma delta T cells can be detected in the lymphocytic infiltrate within breast carcinomas. These data showing that V delta 2+ T cells can recognize and kill cells of breast carcinoma lineage in vitro, and that cells expressing V delta 2 genes in their T cell receptor structure can be detected in the tumor, suggest that further studies of the nature of the interactions between V delta 2 T cells and breast carcinoma cells are warranted.

Antibodies, Monoclonal↗
PubMed1993

The role of childbirth in smoking cessation.

BACKGROUND: Many women abstain from smoking during pregnancy, but relapse rates in the first year postpartum are high. The impact of childbirth on long-term abstinence from smoking is unknown for both women and men. METHODS: We assessed the impact of childbirth on long-term abstinence from smoking (minimum: 17 months, much longer in most cases) in a retrospective cohort analysis of 925 women and 1,494 men who were interviewed in 1984 to 1986 in the national baseline survey of the German Cardiovascular Prevention Study. RESULTS: Among women, smoking cessation rates resulting in long-term abstinence were about three times higher during the year of childbirth and the year before than in other years (adjusted rate ratio, 2.98; 95% confidence interval, 2.21-4.03). Childbirth was also associated with increased cessation rates among better educated men (adjusted rate ratio for this subgroup, 1.84; 95% confidence interval, 1.16-2.92), but not among less educated men. Nevertheless, childbirth led to long-term abstinence from smoking only in a small minority of smoking mothers and fathers. CONCLUSION: Despite increased cessation rates around childbirth, more effective measures are needed to promote sustained abstinence after childbirth among both parents.

Adult↗
PubMed1993

A field study on the immediate effects of exposure to low-altitude flights on heart rate and arrhythmia in patients with cardiac diseases.

Noise from low-altitude military flights differs from most other sources of noise by virtue of its unpredictability in space and time, its very high maximal levels, and the fast increase in noise level at high flight speeds. While this makes low-altitude flights a frightening and annoying experience, the potential immediate health hazards for exposed individuals with preexisting cardiovascular disease are unclear. A field study on the immediate effects of exposure to low-altitude flights on heart rate and arrhythmia was conducted among patients of a rehabilitation clinic for cardiac diseases in the summer of 1990 in Bad Rothenfelde, Germany. Twenty-four hour electrocardiograms of 68 patients taken on days when low-altitude overflights with peak sound pressure levels above 95 dB(A) were registered on the flat roof of the clinic were analyzed for changes in the heart rate or the occurrence of ventricular extrasystoles in four 2-min periods before, around, and after the overflights. Overall, 149 "overflight events" were included in the analysis. No major changes in the heart rate or in the frequency of ventricular extrasystoles were observed, but this could be partly due to problems inherent in the field approach. Nevertheless, the potential effects on heart rate and arrhythmia of low-altitude flights appear to be of limited magnitude compared to the potential effects of other factors, such as psychological or physical exposures, and they are probably too small to be proven under field conditions in an observational epidemiologic study in Germany following the limitations placed on the frequency and altitude of flights in September 1990.

Aged↗
PubMed1993

Second primary malignancies following gynecological tumours in Saarland, Germany, 1968-1987.

The occurrence of second primary malignancies was assessed among 2922 women with cervical cancer, 2721 women with endometrial cancer and 1745 women with malignant neoplasms of the ovaries, who were notified to the cancer registry of Saarland, Germany, between 1968 and 1987. Analyses are presented for second primary malignancies at any site and at the most important single sites. Among women with cervical cancer, 98 second primary malignancies were observed, slightly fewer than the 99.3 cases that would have been expected on the basis of the incidence rates of the general population (standardized incidence ratio, SIR = 0.99). More second malignancies were observed than expected in the urinary bladder (SIR = 3.51) while the opposite applied to second neoplasms in the breast (SIR = 0.56). Among women with endometrial and ovarian cancer, the numbers of observed cases slightly exceeded the expected numbers for second primary neoplasms at any site (SIR = 1.19 and 1.41 respectively). More second primary neoplasms were observed than expected in the colon, breast, urinary bladder and kidneys among these women. We discuss our results, which are in agreement with findings among North European and North American populations, from clinical and etiological points of view.

Confidence Intervals↗
PubMed1993

Intra-operative transluminal angioplasty of the supra-aortic vessels.

Intra-operative transluminal angioplasty of supra-aortic vessels was performed in 9 patients. All subjects had lesions which were considered difficult or impossible to operate upon. In 2 patients a proximal occlusion of the left subclavian artery was dilated. Seven subjects showed severe stenoses of the supra-aortic vessels: common carotid artery: 1, internal carotid artery: 2, external carotid artery: 1, external carotid artery prosthetic graft: 1, brachiocephalic trunk: 1, vertebral artery: 1. All patients suffered from symptoms which corresponded to the site of the lesions in question. Intra-operative angioplasty was primarily successful in all 9 patients. Re-occlusion occurred within a few days in both patients who underwent angioplasty of the subclavian artery. Six of the seven subjects with stenotic lesions remained free of symptoms and of restenosis. In the case of dilatation of a prosthetic graft of the external carotid artery asymptomatic occlusion developed within 8 weeks. In selected cases intra-operative angioplasty is a potentially valuable alternative in the treatment of surgically inaccessible lesions of the supra-aortic vessels.

Adult↗
PubMed1993

Bias due to non-differential misclassification of polytomous confounders.

This paper addresses potential effects of non-differential misclassification of polytomous confounders on adjusted exposure-disease associations. Although the degree of confounder-misclassification bias heavily depends on the relative distribution of the confounding variable among the compared exposure groups and the misclassification pattern, in most cases the bias is in the same direction (though to a lesser degree) than the confounding, i.e. the observed adjusted measures lie between the crude and the fully adjusted measures. In some instances, however, the confounder misclassification bias may be in the opposite direction. This is in contrast to previous understanding that non-differential confounder misclassification always tends to bias adjusted effect estimates towards the crude estimates and that the extent of this bias has a stable relationship to the degree of misclassification. Consequently, conclusions on the potential effects of non-differential misclassification of a polytomous confounder in any given study should only be made after careful sensitivity analyses which consider plausible ranges of misclassification rates.

Bias↗
PubMed1993

The effects of joint misclassification of exposure and disease on epidemiologic measures of association.

This paper addresses the effects of simultaneous misclassification of both exposure and disease on epidemiologic measures of association. If misclassification of a dichotomous exposure is independent of a dichotomous disease status and vice versa (non-differential misclassification), and misclassification of exposure is independent of misclassification of disease, then the bias is always toward the null. In practice, however, errors in exposure and disease ascertainment may often be correlated. In this case, the observed exposure-disease association may be strongly biased in any direction even with non-differential misclassification. As an important corollary, the assertion commonly made in the discussion of epidemiologic study results that the observed measures of association can only be biased toward the null due to presumedly non-differential misclassification has to be viewed as inadequate unless the assertion that exposure and disease misclassification are independent is also justified. Inferences regarding the degree and direction of bias due to misclassification of exposure and disease should consider plausible degrees of correlation in classification errors in addition to the overall misclassification rates. Whenever possible, sensitivity analyses should be performed to provide a quantitative basis for such inferences.

Bias↗
PubMed1993

Second primary neoplasms following breast cancer in Saarland, Germany, 1968-1987.

A statewide cohort study on the occurrence of second primary neoplasms was conducted among 9678 women first diagnosed with breast cancer in Saarland, Germany between 1968 and 1987. A total number of 409 second primary neoplasms was observed compared to 328 cases that would have been expected based on the incidence rates of the general population (standardised incidence ratio, SIR = 1.25). This elevation in incidence of second neoplasms was primarily due to increased occurrence of cancer of the opposite breast (SIR = 2.48), which was most pronounced for patients below the age of 50 (SIR = 4.20) and within the first 5 years after diagnosis (SIR = 2.91). There was a moderate elevation in incidence of malignant tumours of the ovaries (SIR = 1.46), while the incidence of most other malignancies was lower than in the general population. Our results, which are in agreement with previous findings from Northern Europe, the U.S.A. and Japan provide valuable background information for aetiological research, as well as for surveillance of breast cancer patients.

Breast Neoplasms↗
PubMed1993

Inferences on the potential effects of presumed nondifferential exposure misclassification.

In the presentation and discussion of epidemiologic study results, investigators often argue that their results have to be viewed as conservative due to the occurrence of presumedly nondifferential exposure misclassification. Sometimes attempts are made to correct for this supposed bias toward the null. Particularly, various dual exposure measurement strategies that may eliminate or at least reduce the bias if the exposure misclassification is truly nondifferential have gained much popularity in recent years. However, even in cohort studies, it is often questionable whether the exposure misclassification rates are completely independent of measured disease risk. In this article, I assess the effects of violating the assumption of nondifferential misclassification on the direction and magnitude of bias and on the misclassification correction procedures. Even slight violation of the nondifferentiality assumption can lead to large bias away from the null or to crossover bias, particularly if dual measurement procedures are used to correct for exposure misclassification. Consequently, inferences on the potential effects of presumedly nondifferential exposure misclassification in any given study should only be made after careful sensitivity analyses that take into account the full range of plausible misclassification rates as well as of plausible deviations from nondifferentiality.

Bias↗
PubMed1993

Children's exposure to parental smoking in West Germany.

In this study, we derive national estimates of the prevalence of children's exposure to parental smoking in West Germany. The estimates are based on a national health survey conducted in 1987 and refer to those parents living in the same household as the child. Estimated prevalences of maternal smoking range from 18.9% among children aged < 2 years to more than 30% among 2-5 and 6-13 year old children. Estimates of paternal smoking prevalence are considerably higher: 33.7% among children < 2 years old and 43.1% and 46.8% among 2-5 and 6-13 year old children, respectively. The prevalence of at least one smoking household member was 49.9% among 2-5 year old children, while a clear majority of children aged < 2 years (58.8%) and 6-13 (67.5%) were living in a household with at least one smoker. For all age groups, prevalence of maternal and paternal smoking was considerably higher among children of less-educated parents than among children of better-educated parents. Given the high prevalence of parental smoking and the association of parental smoking with a variety of respiratory diseases in children, a large proportion of these diseases could be prevented by efforts to reduce smoking among parents.

Adolescent↗
PubMed1993

Risk and rate advancement periods as measures of exposure impact on the occurrence of chronic diseases.

The predominant epidemiologic measures of risk factor impact have been various concepts of the "attributable fraction." For many chronic diseases, however, risk factors merely advance the occurrence of disease, and traditional concepts of the attributable fraction do not convey information on the time dimension of premature disease occurrence. Measures of years of disease-free life lost have been proposed to reflect this time dimension but are not always estimable without special assumptions. In this paper, we examine two alternative measures, the risk and rate advancement periods, which are the time periods by which the risk or rate of disease is advanced among exposed subjects conditional on disease-free survival to some baseline age. These measures are applicable for risk factors that promote progression of chronic diseases whose rates increase with age. Point and interval estimates of these measures are easily derived from the output of standard modeling analyses. The measures are illustrated with examples from the literature. The uses and limitations of risk and rate advancement periods are critically discussed.

Adult↗
PubMed1993

A birth cohort analysis of the smoking epidemic in West Germany.

STUDY OBJECTIVE: The aim was to provide insights in the spread of the smoking epidemic and eventual progress against cigarette smoking in West Germany. DESIGN: This was a retrospective birth cohort analysis based on a cross sectional national survey. SETTING: The survey was conducted in 1987 by the Ministry of Youth, Family and Health in order to identify priorities for health policy and promotion. The target population were all residents of German nationality above the age of 14 years. STUDY POPULATION: 1721 men and women of the birth cohorts 1911-20, 1921-30, 1931-40, 1941-50, 1951-60, and 1961-70 were included in this analysis (65.7% overall response rate). MEASUREMENTS AND MAIN RESULTS: The participants were asked for their detailed life time history of cigarette smoking in a personal interview. This information was used to calculate and plot historical smoker prevalences by sex, level of school education, birth cohort, and calendar year after correcting for differential survival of smokers and non-smokers. In men, smoking prevalences increased slowly from birth cohort to birth cohort and reached a maximum of more than 70% in the 1941-50 cohort in the early 1970s. While smoker prevalences were considerably lower in the two youngest birth cohorts among better educated men, no major changes were observed in men with lower educational status. The rise of the smoking epidemic in women seems to have levelled off only very recently. CONCLUSIONS: In contrast to other countries with more powerful antismoking campaigns, no major progress in the fight against cigarette smoking has so far been made in West Germany. Major public health efforts are badly needed to limit the epidemic of smoking attributable diseases in this country.

Adolescent↗
PubMed1993

[Projection of new cancer diseases to the year 2002--a contribution to health planning in public health by the Saarland cancer registry].

This paper provides projections of incident cases of malignant neoplasms in Saarland, Germany, between 1988 and 2002. The analyses are based on population forecasts by the National Statistical Office and on age-cohort analyses of cancer incidence data from the population-based cancer registry of the Saarland. Due to dramatic demographic changes and increasing age-specific cancer incidence rates, the average yearly number of total incident cases of malignant neoplasms is projected to increase by 63.1% between 1983-1987 and 1998-2002 in men, with the strongest increase projected for colon cancer (+114.6%). In women, a modest increase (+7.1%) is projected for all malignant neoplasms, with stronger increases for colon cancer (+50.1%), lung cancer (+44%) and breast cancer (+27.4%), whereas decreasing annual numbers of cases are projected for cervical cancer (-51.6%), stomach cancer (-18.5%) and endometrial cancer (-10.2%). The results provide a quantitative basis for health care planning in the Saarland. They may also serve as a rough guide for other parts of Germany for which reliable cancer incidence data are not available.

Adolescent↗
PubMed1992

Intraperitoneal chemotherapy versus no treatment in patients with ovarian carcinoma who are in complete clinical remission.

BACKGROUND: The optimal management of patients with ovarian carcinoma who are in complete clinical remission after completion of postoperative cisplatin-based chemotherapy has not been established. METHODS: In this study, the outcomes of two groups of such patients were compared. One group of 25 patients underwent a second-look laparotomy and subsequently received three courses of intraperitoneal chemotherapy (IP group). The other group of 12 patients was not reexplored and received no additional treatment (NT group). RESULTS: A trend for better survival in the IP group was found compared with the NT group. There was no difference in the duration of the progression-free interval. CONCLUSIONS: More effective treatment for the consolidation of complete clinical remission in patients with ovarian carcinoma is needed.

Aged↗