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Biomedical subjects

J Wellmann

Publications and source records attributed to J Wellmann.

15 recordsLinked to original sources
PubMed2006

A randomized controlled trial comparing hydration therapy to additional hemodialysis or N-acetylcysteine for the prevention of contrast medium-induced nephropathy: the Dialysis-versus-Diuresis (DVD) Trial.

Contrast medium-induced nephropathy (CIN) is a serious complication with increasing frequency and an unfavorable prognosis. Previous analyses of surrogate parameters have suggested beneficial effects of hemodialysis that are assessed in this randomized clinical trial. We performed a prospective single-center trial in 424 consecutive patients with serum creatinine concentrations between 1.3- 3.5 mg/dl who underwent elective coronary angiography. Patients were randomized to one of three treatment strategies with all patients receiving pre- and postprocedural hydration: One group received no additional therapy, patients in the second group were hemodialyzed once, and the third group received oral N-acetylcysteine. The frequency of CIN (defined as an increase in serum creatinine>or=0.5 mg/dl) from 48 to 72 h after catheterization was 6.1% in the hydration-only group, 15.9% with hemodialysis treatment, and 5.3% in the N-ACC group (intention-to-treat analysis; P=0.008). There were no differences between the treatment groups with regard to increased (>or=0.5 mg/dl) serum creatinine concentrations after 30-60 days (4.8%, 5.1%, and 3.1%, respectively; P=0.700). Analyses of long-term follow-up (range 63 to 1316 days) by Cox regressions models of the study groups found quite similar survival rates (P=0.500). In contrast to other (retrospective) studies, long-term survival of patients with vs those without CIN within 72 h was not different, but patients who still had elevated creatinine concentrations at 30-60 days suffered from a markedly higher 2-year mortality (46% vs 17%, P=0.002). In conclusion, hemodialysis in addition to hydration therapy for the prevention of CIN provided no evidence for any outcome benefit but evidence for probable harm. Increased creatinine concentrations at 30-60 days, but not within 72 h, were associated with markedly reduced long-term survival.

Acetylcysteine↗
PubMed2006

Cancer mortality in German carbon black workers 1976-98.

BACKGROUND: Few studies have investigated cancer risks in carbon black workers and the findings were inconclusive. METHODS: The current study explores the mortality of a cohort of 1535 male German blue-collar workers employed at a carbon black manufacturing plant for at least one year between 1960 and 1998. Vital status and causes of death were assessed for the period 1976-98. Occupational histories and information on smoking were abstracted from company records. Standardised mortality ratios (SMR) and Poisson regression models were calculated. RESULTS: The SMRs for all cause mortality (observed deaths (obs) 332, SMR 120, 95% CI 108 to 134), and mortality from lung cancer (obs 50, SMR 218, 95% CI 161 to 287) were increased using national rates as reference. Comparisons to regional rates from the federal state gave SMRs of 120 (95% CI 107 to 133) and 183 (95% CI 136 to 241), respectively. However, there was no apparent dose response relationship between lung cancer mortality and several indicators of occupational exposure, including years of employment and carbon black exposure. CONCLUSIONS: The mortality from lung cancer among German carbon black workers was increased. The high lung cancer SMR can not fully be explained by selection, smoking, or other occupational risk factors, but the results also provide little evidence for an effect of carbon black exposure.

Adult↗
PubMed2006

Markov models for repeated ordinal data.

OBJECTIVES: To demonstrate the application of Markov models, especially for ordinal outcomes, within the context of regression models for correlated data. METHODS: A brief review of regression methods for correlated data is given. A proportional odds model and a continuation ratio model is applied to repeated measurements of macular pigment density, obtained in an intervention study on the supplementation of macular carotenoids. The correlation between repeated assessments is assumed to follow a first-order Markov model. The models are implemented with standard statistical software. RESULTS: Both models, though not directly comparable, provide a similar conclusion. The application of these models with standard statistical software is straightforward. CONCLUSIONS: Markov models can be valuable alternatives to random effects modes or procedures based on generalized estimation equations.

Carotenoids↗
PubMed2004

Different methods to calculate effect estimates in cross-sectional studies. A comparison between prevalence odds ratio and prevalence ratio.

OBJECTIVES: According to results from the epidemiological literature, it can be expected that the prevalence odds ratio (POR) and the prevalence ratio (PR) differ with increasing disease prevalence. We illustrate different concepts to calculate these effect measures in cross-sectional studies and discuss their advantages and weaknesses, using actual data from the ISAAC Phase III cross-sectional survey in Münster, Germany. METHODS: We analyzed data on the association between self-reported traffic density and wheeze and asthma by means of the POR, obtained from a logistic regression, and the PR, which was estimated from a log-linear binomial model and from different variants of a Poisson regression. RESULTS: The analysis based on the less frequent disease, i.e. asthma with an overall prevalence of 7.8%, yielded similar results for all estimates. When wheezing with a prevalence of 17.5% was analyzed, the POR produced the highest estimates with the widest confidence intervals. While the point estimates were similar in the log-binomial model and Poisson regression, the latter showed wider confidence intervals. When we calculated the Poisson regression with robust variances, confidence intervals narrowed. CONCLUSIONS: Since cross-sectional studies often deal with frequent diseases, we encourage analyzing cross-sectional data based on log-linear binomial models, which is the 'natural method' for estimating prevalence ratios. If algorithms fail to converge, a useful alternative is to define appropriate starting values or, if models still do not converge, to calculate a Poisson regression with robust estimates to control for overestimation of errors in the binomial data.

Adolescent↗
PubMed2003

[Classical risk factors for myocardial infarction and total mortality in the community--13-year follow-up of the MONICA Augsburg cohort study].

PURPOSE: The MONICA (MONItoring of trends and determinants in CArdiovascular disease) project in the region of Augsburg, Southern Germany, is the first population-based cohort study in Germany investigating the association of the risk factors hypertension, hypercholesterolemia and smoking with incident myocardial infarction and total mortality, and to assess their impact at the population level. METHODS: At baseline, 1074 men and 1013 women aged 45-64 years were randomly selected from the population in the Augsburg region and extensively interviewed and examined regarding their cardiovascular risk profile. They were traced over 13 years from 1984-1997. We calculated incidence rates, hazard rate ratios, population attributable risks (PAR), and rate advancement periods (RAP) according to the three risk factors and their combinations. RESULTS: Among men, 107 myocardial infarctions and 204 total mortality events occurred during the study period; in women the number of total mortality cases was 102. The three classical risk factors were associated with incident myocardial infarction in men and with total mortality in men and women over a period of 13 years. Heavily smoking men had a particularly high risk of total mortality (HRR=4.2; 95% CI 2.5-7.0) and myocardial infarction (HRR=3.8; 1.9-7.6). Men with treated hypertension were at equally high risk for both total mortality (HRR=2.4; 1.5-3.7) and myocardial infarction (HRR=2.4; 1.3-4.3). In women, treated hypertension (HRR=2.5; 1.5-4.1) and hypercholesterolemia (HRR=2.0; 1.2-3.3) were most strongly related to total mortality. Regarding the association of risk factor combinations and myocardial infarction among men, the presence of all three risk factors simultaneously (HRR=7.9; 3.6-17.3) and the combination smoking/hypercholesterolemia (HRR=5.8; 3.2-10.5) were particularly hazardous. In total, the three risk factors contributed 54% of the burden of myocardial infarction in the male study population. The rate advancement periods for myocardial infarction related to treated hypertension, hypercholesterolemia and heavy smoking were 10.5, 5.8 and 15.8 years, respectively. CONCLUSIONS: Our results confirm the outstanding impact of the classical risk factors on myocardial infarction and total mortality in a southern German population. Coronary heart disease is largely preventable through risk factor reduction. Therefore, risk factor counselling, education and treatment are crucial to prevent people from developing the disease or dying prematurely.

Cohort Studies↗
PubMed2002

On the potential of measurement error to induce differential bias on odds ratio estimates: an example from radon epidemiology.

It is well established that odds ratios estimated by logistic regression are subject to bias if exposure is measured with error. The dependence of this bias on exposure parameter values, particularly for multiplicative measurement error, and its implications in epidemiology are not, however, as fully acknowledged. We have been motivated by a German West case-control study on lung cancer and residential radon, where restriction to a subgroup exhibiting larger mean and variance of exposure than the entire group has shown higher odds ratio estimates as compared to the full analysis. By means of correction formulae and simulations, we show that bias from additive classical type error depends on the exposure variance, not on the exposure mean, and that bias from multiplicative classical type error depends on the geometric standard deviation (in other words on the coefficient of variation of exposure), but not on the geometric mean of exposure. Bias from additive or multiplicative Berkson type error is independent of exposure distribution parameters. This indicates that there is a potential of differential bias between groups where these parameters vary. Such groups are commonly compared in epidemiology: for example when the results of subgroup analyses are contrasted or meta-analyses are performed. For the German West radon study, we show that the difference of measurement error bias between the subgroup and the entire group exhibits the same direction but not the same dimension as the observed results. Regarding meta-analysis of five European radon studies, we find that a study such as this German study will necessarily result in smaller odds ratio estimates than other studies due to the smaller exposure variance and coefficient of variation of exposure. Therefore, disregard of measurement error can not only lead to biased estimates, but also to inconsistent results and wrongly concluded effect differences between groups.

Air Pollutants, Radioactive↗
PubMed2002

Mechanistic modelling in large case-control studies of lung cancer risk from smoking.

The two-step clonal expansion (TSCE) model is applied to large case-control studies, frequency matched for age, which allow estimation of the RR of lung tumour risk caused by smoking. For estimating background hazard rates, mortality data from the study areas are used to supplement the case-control data. Two approaches are used to analyse the data, based on the unconditional and the conditional likelihoods. They are demonstrated to give nearly identical results. Some model diagnostics are performed and demonstrate a good model fit. Our results indicate that smoking acts on the promotion and transformation parameters, but not on the initiation parameter of the TSCE model. The fitted relative risk of current smokers peaks between ages 50 and 60 years. The relative risk of male ex-smokers decreases strongly with time since end of exposure, but does not reach the risk of non-smokers, and does not decrease as much as for female ex-smokers.

Adult↗
PubMed2002

[Secondary prevention of coronary heart disease. Results from EuroASPIRE I and II in the region of Münster, Germany].

BACKGROUND: EuroASPIRE (European Action on Secondary Prevention through Intervention to Reduce Events) is a European multicenter study on secondary prevention in patients with coronary heart disease (CHD). The first cross-sectional survey was undertaken in 1995/96 among 3569 patients from nine countries. A second cross-sectional survey (EuroASPIRE II) was conducted in 1999/2000 among 5556 patients from 15 countries to evaluate among others whether coronary prevention had improved since the first. METHODS: The present study was conducted in the region of Münster, Germany, as part of the EuroASPIRE study. Consecutive patients, men and women up to 70 years of age with established CHD, were identified retrospectively. A total of 392 (EuroASPIRE I) and 402 (EuroASPIRE II) patients participated. Information on cardiovascular risk factors, lifestyle and medication were obtained through medical records, interviews and examinations. RESULTS: Both studies demonstrate a high prevalence of risk factors among CHD patients. At the time of the interview more than 60% of the patients in both surveys had two or more risk factors. The comparison of EuroASPIRE I and II reveals a substantial decrease of 20% in the prevalence of hypercholesterolemia, but an increase in the prevalence of hypertension and obesity. ACE-inhibitors, betablockers and lipid lowering drugs, especially statins, were used more frequently in EuroASPIRE II. CONCLUSIONS: We conclude that secondary prevention of CHD in the region of Münster like in the other European study regions is less than optimal and has not substantially improved between 1996 and 2000. Potential reasons are discussed.

Adult↗
PubMed2001

Lung cancer in lifetime nonsmoking men - results of a case-control study in Germany.

Epidemiological studies of lung cancer among nonsmoking men are few. This case-control study was conducted among lifetime nonsmoking men between 1990 and 1996 in Germany to examine lung cancer risk in relation to occupation, environmental tobacco smoke, residential radon, family history of cancer and previous lung disease. A total of 58 male cases with confirmed primary lung cancer and 803 male population controls who had never smoked more than 400 cigarettes in their lifetime were personally interviewed by a standardized questionnaire. In addition, 1-year radon measurements in the living and bedroom of the subjects' last dwelling were carried out. Unconditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI). Having ever worked in a job with known lung carcinogens was associated with a two-fold significantly increased lung cancer risk (OR = 2.2; CI = 1.0-5.0), adjusted for age and region. The linear trend test for lung-cancer risk associated with radon exposure was close to statistical significance, demonstrating an excess relative risk for an increase in exposure of 100 Bq m(-3)of 0.43 (P = 0.052). Nonsignificantly elevated effects of exposure to environmental tobacco smoke in public transportation and in social settings were observed. No associations with a family history of cancer or previous lung diseases were found. Our results indicate that occupational carcinogens and indoor radon may play a role in some lung cancers in nonsmoking men.

Adenocarcinoma↗
PubMed2001

Case-control study on lung cancer and residential radon in western Germany.

In a 1990-1996 case-control study in western Germany, the authors investigated lung cancer risk due to exposure to residential radon. Confirmed lung cancer cases from hospitals and a random sample of community controls were interviewed by trained interviewers regarding different risk factors. For 1 year, alpha track detectors were placed in dwellings to measure radon gas concentrations. The evaluation included 1,449 cases and 2,297 controls recruited from the entire study area and a subsample of 365 cases and 595 controls from radon-prone areas of the basic study region. Rate ratios were estimated by using conditional logistic regression adjusted for smoking and for asbestos exposure. In the entire study area, no rate ratios different from 1.0 were found; in the radon-prone areas, the adjusted rate ratios for exposure in the present dwelling were 1.59 (95% confidence interval (CI): 1.08, 2.27), 1.93 (95% CI: 1.19, 3.13), and 1.93 (95% CI: 0.99, 3.77) for 50-80, 80-140, and >140 Bq/m3, respectively, compared with 0-50 Bq/m3. The excess rate ratio for an increase of 100 Bq/m3 was 0.13 (-0.12 to 0.46). An analysis based on cumulative exposure produced similar results. The results provide additional evidence that residential radon is a risk factor for lung cancer, although a risk was detected in radon-prone areas only, not in the entire study area.

Adenocarcinoma↗
PubMed2000

The use of sliding time windows for the exploratory analysis of temporal effects of smoking histories on lung cancer risk.

To examine the time-dependent effects of exposure histories on disease we use sliding time windows as an exploratory alternative to the analysis of variables like time since last exposure and duration of exposure. The method fits a series of risk models which contain total cumulative exposure and an additional covariate for exposures received during fixed time intervals. Characteristics of the fitted models provide insight into the influence of exposure increments at different times on disease risk. A simulation study is performed to check the validity of the approach. We apply the method to data from a recent German case-control study on smoking and lung cancer risk with about 4300 lung cancer cases and a similiar number of controls. The sliding time window approach indicates that the amount of cigarettes smoked from two to 11 years before disease incidence is most predicitive of lung cancer incidence. Among different smoking profiles that result in the same lifelong cumulative number of cigarettes smoked, those with a concentration of smoked cigarettes within 20 years before interview bear substantially larger risk than others.

Aged↗
PubMed2000

Models for retrospective quantification of indoor radon exposure in case-control studies.

In epidemiologic studies on lung cancer risk due to indoor radon the quantification of individual radon exposure over a long time period is one of the main issues. Therefore, radon measurements in one or more dwellings, which in total have been inhabited by the participants for a sufficient time-period, are necessary as well as consideration of changes of building characteristics and ventilation habits, which influence radon concentration. Given data on 1-y alpha-track measurements and personal information from 6,000 participants of case-control studies in West and East Germany, an improved method is developed to assess individual radon exposure histories. Times spent in different rooms of the dwelling, which are known from a personal questionnaire, are taken into account. The time spent outside the house (average fraction 45%) varies substantially among the participants. Therefore, assuming a substantially lower radon exposure outside the dwelling, the residence time constitutes an important aspect of total radon exposure. By means of an analysis of variance, important determinants of indoor radon are identified, namely constant conditions such as type of house (one family house or multiple dwelling), type of construction (half-timbered, massive construction, lightweight construction), year of construction, floor and type of basement, and changeable conditions such as heating system, window insulation, and airing habits. A correction of measurements in former dwellings by factors derived from the analysis is applied if current living conditions differ from those of the participants at the time when they were living in the particular dwellings. In rare cases the adjustment for changes leads to a correction of the measurements with a factor of about 1.4, but a reduction of 5% on average only. Exposure assessment can be improved by considering time at home and changes of building and ventilation conditions that affect radon concentration. The major concern that changes in ventilation habits and building conditions lead to substantial errors in exposure (and therefore risk) assessment cannot be confirmed in the data analyzed.

Air Pollutants, Radioactive↗
PubMed2000

Analysis of exposure-time-response relationships using a spline weight function.

To examine the time-dependent effects of exposure histories on disease, we estimate a weight function within a generalized linear model. The shape of the weight function, which is modeled as a cubic B-spline, gives information about the impact of exposure increments at different times on disease risk. The method is evaluated in a simulation study and is applied to data on smoking histories and lung cancer from a recent case-control study in Germany.

Biometry↗
PubMed1997

Serum immunoglobulin level and skin prick test response.

OBJECTIVE: The relation of viral infections and allergic diseases is inconclusive. The objective of the analysis therefore was to examine the relation between immunoglobulin levels and sensitization to common allergens as measured by the skin prick test (SPT). METHODS: In a population-based study of 2,470 children, 2,188 skin prick tests, and 2,042 blood samples could be analyzed. RESULTS: At least one positive SPT was observed in 19.2% of the children. IgA und IgG levels did not show any association with SPT response. As expected, there was a sharp increase in the two highest quartile groups of IgE (p for trend <0.0001), while the prevalence of positive SPT continuously decreased with higher IgM levels (p for trend 0.002). This effect of IgM could be seen for all allergens examined. If an upper respiratory tract infection was reported one week prior to testing, the prevalence of a positive SPT was also reduced by nearly one half, however, this association was not significant. CONCLUSIONS: Since IgM has a half-life of approximately 5 days, the inverse association found between IgM and the prevalence of positive SPT seems to be a transient effect of a prior infection.

Allergens↗