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Biomedical subjects

Ulf Strömberg

Publications and source records attributed to Ulf Strömberg.

At least 19 recordsLinked to original sources
PubMed2006

Weight and height at 4 and 7 years of age in children born to mothers with a high intake of fish contaminated with persistent organochlorine pollutants.

In Sweden the main exposure route for persistent organochlorine pollutants (POP) is through consumption of fatty fish from the Baltic Sea (off the eastern coast). The present study aimed to investigate whether intrauterine exposure for POP may have negative impact on children's weight and height at 4 and 7 years of age, respectively. The study included 174 fishermen's wives from the Swedish east coast who had given birth to an infant with either low (n=55) or normal (n=119) birth weight, and 88 and 206 corresponding women from the Swedish west coast (where the fish is less polluted). Comparisons between the east and west coast cohorts were performed. In addition, blood samples were collected among the east coast women and the concentrations of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) in plasma was analyzed and estimated for the year of childbirth. There were no significant differences between the east and west coast cohorts regarding weight and height at 4 and 7 years of age. There were, however, significant negative associations between the estimated plasma concentrations of CB-153 during year of childbirth and weight at 4 and 7 years of age, respectively, among the normal birth weight children. The study gives only very weak support for the hypothesized association.

Animals↗
PubMed2005

Prognostic significance of chromosome aberrations in high-grade soft tissue sarcomas.

PURPOSE: To investigate whether previously observed correlations between tumor karyotype and risk of metastases could be reproduced in an independent set of high-grade soft tissue sarcomas (STSs). PATIENTS AND METHODS: In a previous study on high-grade STSs with clonal chromosome aberrations, we identified a number of cytogenetic variables, besides tumor grade and size, that were associated with significantly increased risk of metastases. In the present study, we have tested the predictive value of these cytogenetic variables in a new set of 156 high-grade STSs, all located in the extremities or trunk wall. RESULTS: Of the 10 cytogenetic variables that turned out to provide prognostic information in the previous series, encompassing 122 trunk wall or extremity STSs, three were significantly associated with metastases also in the new series. In a final Cox regression analysis including these three cytogenetic variables, as well as tumor grade and size, on the combined series of 278 high-grade STSs, four parameters were found to be significantly associated with metastasis risk: tumor grade 3, tumor size > or = 5 cm, breakpoint in region 1p1, and gain of region 6p1. CONCLUSION: Our findings suggest that independent prognostic information may be gained from cytogenetic analysis of high-grade STS.

Adult↗
PubMed2005

Are associations between socio-economic characteristics and exposure to air pollution a question of study area size? An example from Scania, Sweden.

BACKGROUND: Numerous studies have shown that exposure to air pollutants in the area of residence and the socio-economic status of an individual may be related. Therefore, when conducting an epidemiological study on the health effect of air pollution, socio-economy may act as a confounding factor. In this paper we examine to what extent socio-economic status and concentrations of NO2 in the county/region of Scania, southern Sweden, are associated and if such associations between these factors differ when studying them at county or city level. To perform this study we used high-resolution census data and modelled the annual exposure to NO2 using an emission database, a dispersion modelling program and a geographical information system (GIS). RESULTS: The results from this study confirm that socio-economic status and the levels of NO2 in the area of residence are associated in some cities. The associations vary considerably between cities within the same county (Scania). Even for cities of similar sizes and population bases the associations observed are different. Studying the cities together or separately yields contradictory results, especially when education is used as a socio-economic indicator. CONCLUSION: Four conclusions have been drawn from the results of this study. 1) Adjusting for socio-economy is important when investigating the health effects of air pollution. 2) The county of Scania seems to be heterogeneous regarding the association between air pollution and socio-economy. 3) The relationship between air pollution and socio-economy differs in the five cities included in our study, depending on whether they are analysed separately or together. It is therefore inadvisable to determine and analyse associations between socio-economy and exposure to air pollutants on county level. This study indicates that the size and choice of study area is of great importance. 4) The selection of socio-economic indices (in this study: country of birth and education level) is important.

Journal Article↗
PubMed2005

Tubular and glomerular kidney effects in Swedish women with low environmental cadmium exposure.

Cadmium is a well-known nephrotoxic agent in food and tobacco, but the exposure level that is critical for kidney effects in the general population is not defined. Within a population-based women's health survey in southern Sweden (Women's Health in the Lund Area, WHILA), we investigated cadmium exposure in relation to tubular and glomerular function, from 1999 through early 2000 in 820 women (71% participation rate) 53-64 years of age. Multiple linear regression showed cadmium in blood (median, 0.38 microg/L) and urine (0.52 microg/L; density adjusted = 0.67 microg/g creatinine) to be significantly associated with effects on renal tubules (as indicated by increased levels of human complex-forming protein and N-acetyl-beta-D-glucosaminidase in urine), after adjusting for age, body mass index, blood lead, diabetes, hypertension, and regular use of nephrotoxic drugs. The associations remained significant even at the low exposure in women who had never smoked. We also found associations with markers of glomerular effects: glomerular filtration rate and creatinine clearance. Significant effects were seen already at a mean urinary cadmium level of 0.6 microg/L (0.8 microg/g creatinine). Cadmium potentiated diabetes-induced effects on kidney. In conclusion, tubular renal effects occurred at lower cadmium levels than previously demonstrated, and more important, glomerular effects were also observed. Although the effects were small, they may represent early signs of adverse effects, affecting large segments of the population. Subjects with diabetes seem to be at increased risk.

Acetylglucosaminidase↗
PubMed2005

Model specification and unmeasured confounders in partially ecologic analyses based on group proportions of exposed.

OBJECTIVES: The aim of this study was to quantify bias from a partially ecologic analysis due to (i) model misspecification and (ii) an unmeasured confounder, considering various scenarios that may occur in occupational and environmental epidemiology. A study with an aggregate exposure variable, PE, but with outcome, group membership, and covariates assessed individually is partially ecologic. In this paper, PE is the proportion exposed; PE can vary across geographic areas or occupational groups. METHODS: Several hypothetical scenarios were considered, varying the baseline risk, the exposure effect, the exposure distribution across groups, the impact of the (unmeasured) confounder, and the confounder distribution across groups. First, confounding within groups was introduced. Thereafter, confounding between groups was introduced by co-varying PE and the confounder prevalence across the groups. The expected odds ratio (exposed versus unexposed) was calculated in two alternative models, the logistic regression and linear odds models, both with PE as the independent variable. Moreover, empirical data on noise exposure and sleeping disturbances were analyzed. RESULTS: Compared with the logistic regression model, the linear odds model yielded a markedly less biased odds ratio (OR) when the outcome was rare (< or = 5% baseline risk). Confounding within groups resulted in marginal bias, whereas confounding between groups resulted in more pronounced bias. CONCLUSIONS: A logistic regression analysis, with PE as an independent variable, can yield substantial model misspecification bias. By contrast, the linear odds model is valid when the outcome is rare. Confounding between groups should be of more concern than confounding within groups in partially ecologic analyses.

Bias↗
PubMed2004

Impact of types of lymphocyte chromosomal aberrations on human cancer risk: results from Nordic and Italian cohorts.

The frequency of cells with structural chromosomal aberrations (CAs) in peripheral blood lymphocytes is the first genotoxicity biomarker that has shown an association with cancer risk. CAs are usually divided into chromosome-type (CSAs) and chromatid-type aberrations (CTAs), with different mechanisms of formation. From a mechanistic point of view, it is of interest to clarify whether the cancer predictivity of CAs is different with respect to CSAs and CTAs. We report here cancer risk for cytogenetically tested, healthy subjects with respect to frequency of CAs, CSAs, and CTAs in peripheral blood lymphocytes, using Nordic (1981 subjects with CA data, 1871 subjects with CSA/CTA data) and Italian (1573 subjects with CA data, 877 subjects with CTA/CSA data) cohorts, with a median follow-up of 17 years. High levels of CAs at test were clearly associated with increased total cancer incidence in the Nordic cohorts and increased total cancer mortality in the Italian cohort. In the Nordic cohorts, significantly elevated cancer risks were observed for subjects with both high CSAs and high CTAs at test, and these variables showed equally strong cancer predictivity. The results of the Italian cohort did not indicate any clear-cut difference in cancer predictivity between the CSA and CTA biomarkers. There was no significant effect modification by age at test, gender, country, or time since test. The results suggest that both DNA double-strand breaks and other initial DNA lesions responsible for CSAs and CTAs are associated with cancer risk.

Chromatids↗
PubMed2004

Altered menstrual cycles in women with a high dietary intake of persistent organochlorine compounds.

Dietary exposure to persistent organochlorine compounds (POCs) has been found to affect the menstrual cycle in both animals and humans. In Sweden, the major exposure route for POCs is the consumption of fatty fish from the Baltic Sea. Thus, women who eat relatively large amounts of this fish constitute a suitable study group when investigating a possible association between dietary exposure to POC and menstrual cycle disruption. Questionnaires were sent to the exposed women, as well as to a socioeconomically similar cohort of controls, and information was collected on their menstrual cycles. Since the exposed women tended to smoke more than the controls, all results were adjusted for smoking habits. A cohort comparison found that the exposed women on average had 0.46 (95% confidence interval: 0.03, 0.89) days shorter menstrual cycles than controls. However, within the exposed cohort no effects were found of the proxy variables early life exposure and high consumption of Baltic Sea fatty fish. The results give some support to previous results from studies on women with similar exposure, but are not conclusive with respect to whether there is a causal association between POC exposure and menstrual cycle disruption.

Adolescent↗
PubMed2004

Polychlorinated biphenyls in serum and time to pregnancy.

Polychlorinated biphenyls (PCBs) may affect the female reproductive system in both animals and humans. In Sweden, a main exposure source to PCBs is consumption of fatty fish from the Baltic Sea. From 165 female consumers of such fish (fishermen's sisters), information on time to pregnancy (TTP) and miscarriages was collected, blood was drawn, and serum was analyzed for 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153), a biomarker for total PCB exposure. TTP and miscarriage data, as well as plasma CB-153 concentrations, for 121 fishermen's wives were available from previous studies. Thus, information on 286 women was available for investigation of whether a high exposure to PCB affects fertility negatively by increasing the TTP. The concentrations of CB-153 at the time of conception were estimated and trichotomized into low, medium, and high exposure groups. When we analyzed the joint data set of fishermen's wives and fishermen's sisters, a decrease rather than an increase in TTP was indicated for women in the medium (fecundability ratio 1.27 [95% confidence interval 0.89-1.82]) and high (fecundability ratio 1.42 [0.99-2.03]) exposure groups compared to those in the low exposure group. Similar results were found when we stratified on the original data set (fishermen's wives and fishermen's sisters) or childhood exposure. Women with miscarriages had lower estimated past CB-153 concentrations than women with live births. Our data provide no evidence of a hazardous effect associated with CB-153 concentration in the exposure range assessed. The exposure levels found in the fishermen's families, although high compared to that in the general Swedish population, may not be high enough to negatively affect fertility.

Abortion, Spontaneous↗
PubMed2004

Oral Pentasa in the treatment of active Crohn's disease: A meta-analysis of double-blind, placebo-controlled trials.

BACKGROUND & AIMS: The aim of this study was to perform a meta-analysis of the efficacy results from 3 placebo-controlled multicenter clinical trials of slow-release mesalamine (Pentasa) for the acute treatment of mild to moderate Crohn's disease. METHODS: Three trials fulfilled the selection criteria (double-blind, placebo-controlled, randomized studies in adult patients treated with Pentasa 4 g/day for active Crohn's disease). The efficacy and safety was evaluated in these trials by using the Crohn's Disease Activity Index (CDAI) as the primary efficacy variable. The study duration was 16 weeks in all 3 trials. The total numbers of patients were 304 in the Pentasa 4-g/day treatment groups and 311 in the placebo groups. A meta-analysis was performed based on the study reports. RESULTS: For the intent-to-treat patients in the Pentasa groups, the overall mean reduction of the CDAI from baseline to the final visit was -63 points. The corresponding CDAI change in the placebo groups was -45 points; the net difference was -18 points. Compared with placebo, the 4-g/day dose of Pentasa was associated with a statistically significant overall improvement in the CDAI from baseline to the final visit (P = 0.04). When the meta-analysis was restricted to protocol correct patients, the effect of Pentasa became more pronounced (overall mean reduction of -83 CDAI points; P = 0.02, compared with placebo). Contrary to the consistent effects with Pentasa, the trial-specific reductions of the CDAI with placebo differed significantly between the trials. CONCLUSIONS: The meta-analysis of 3 large, double-blind, randomized studies in the treatment of active Crohn's disease confirms that Pentasa 4 g/day is superior to placebo in reducing the CDAI but the clinical significance of the magnitude of this difference is not clear.

Adult↗
PubMed2004

Incorporating group-level exposure information in case-control studies with missing data on dichotomous exposures.

In case-control studies with exposure data obtained from interviews, participation is an issue of concern. Use of external group-level exposure information, available for all cases and controls (including nonparticipants), can reduce participation bias and improve precision of effect estimates. Our methodologic investigation was motivated by a population-based case-control study on occupational exposures and leukemia. We assessed exposure using dichotomous data collected in interviews, and also using census data on past and current occupational groups for all subjects. Based on information from a job-exposure database, a group-level probability of exposure was assigned to each subject. We studied the performance of the iterative expectation-maximization method for estimating the odds ratio (OR) by using the individual-level exposure data on the interviewed participants together with the assigned group-level exposure probabilities for the nonparticipants. In each iteration, the expected numbers of exposed and unexposed among the nonparticipating cases and controls were calculated from their assigned exposure probabilities and, for the cases only, from the current OR estimate. We then estimated the OR based on the total (observed plus expected) numbers and repeated the procedure until convergence. The expectation-maximization method eliminated participation bias and improved precision for scenarios with error-free group-level exposures and individual-level exposure data missing at random conditional on disease status and group affiliation. We specifically addressed consequences of assigning erroneous exposure probabilities to the nonparticipating subjects. In such situations, the expectation-maximization method can produce biased estimates if the participation rates among the cases and controls differ substantially.

Bias↗
PubMed2004

Doubled mortality rate in irradiated patients reoperated for regrowth of a macroadenoma of the pituitary gland.

BACKGROUND: Reduced life expectancy has been shown in patients with hypopituitarism, mainly caused by cardiovascular diseases. A major cause of hypopituitarism is pituitary adenomas, and radiotherapy may be employed as a treatment modality to reduce the post-operative regrowth rate of these tumours. Recently, we showed that in patients with craniopharyngiomas, tumour regrowth foreshadowed a fourfold risk increase for death. For patients with pituitary adenomas, the impact of regrowth on life expectancy is, however, not known. OBJECTIVE: To assess the impact of a reoperation due to a regrowth of a pituitary macroadenoma on mortality, taking into account other candidate prognostic factors. DESIGN AND PATIENTS: In 281 patients with operated and irradiated macroadenomas, excluding acromegaly and Cushing's disease, 35 patients had a regrowth (median follow-up 16.6 years). Possible risk factors for tumour regrowth were investigated by Cox regression models. RESULTS: For tumour regrowth, age, calendar time at primary surgery, gender and extension of tumour growth had no statistically significant impact. For younger patients, the proportion of regrowths was higher, but after age-stratified Cox regression analysis only regrowth was shown to have a significant impact on mortality, with a more than doubled mortality risk for patients with tumour regrowth as compared with the non-regrowing tumour patients (hazard ratio=2.24, P<0.001). This finding was corroborated by cohort analyses using the general population as an external comparison group. CONCLUSION: Among patients with irradiated pituitary macroadenomas, excluding acromegaly and Cushing's disease, a doubled mortality rate was observed for those reoperated for tumour regrowth as compared with patients with non-regrowing tumours.

Adenoma↗
PubMed2004

Epidemiological evaluation of cytogenetic biomarkers as potential surrogate end-points for cancer.

Various occupational exposures have been monitored by chromosomal aberrations, sister chromatid exchanges and micronuclei in peripheral blood lymphocytes. During the last decade, epidemiological studies have evaluated whether any of these markers foreshadows cancer risk. Results from Nordic, Italian and Czech cohorts support an approximately twofold cancer risk among subjects with high frequencies of chromosomal aberrations, but no such association was seen for any of the other biomarkers. The estimated attributable proportion of high frequencies of chromosomal aberrations for overall cancer risk is 0.25, which gives a quantitative estimate of the chromosomal aberration assay as a surrogate endpoint of cancer. The results from the different cohort studies are contradictory in terms of whether or not the predictive value of the chromosomal aberration assay for cancer is differential with respect to occupational exposure to clastogens. Genetic susceptibility factors are known to affect the frequency of chromosomal aberrations in peripheral blood lymphocytes. It is quite possible that such factors might also affect the frequency of chromosomal aberrations directly or might modify the impact of exposures to clastogen. There is no other biomarker for general cancer risk that is applicable to healthy subjects from the general population with such a high attributable proportion. However, at present only a simplified and tentative model can be proposed for the role of the chromosomal aberration marker in the pathogenesis of cancer.

Biomarkers↗
PubMed2003

Cytogenetic and morphologic subgroups of myelodysplastic syndromes in relation to occupational and hobby exposures.

OBJECTIVES: This study investigated the association between occupational and hobby exposure and the risk of myelodysplastic syndromes (MDS) while focusing on differential patterns of clonal chromosome aberrations and morphologic subgroups. METHODS: A case-referent study was conducted with 330 MDS patients investigated cytogenetically in 1976-1993 (cases) and matched referents. Telephone interviews with either the person or a next-of-kin were used. The participation rate of the cases and referents was 85% and 60%, respectively. Information was obtained from the next-of-kin more often for the cases (88%) than for the referents (26%). Occupational hygienists assessed the exposure using interview data on worktasks and hobbies. Associations with disease risk were evaluated for 10 exposures with a logistic regression analysis. RESULTS: The investigated exposures were generally not associated with cytogenetically abnormal MDS. Effect estimates for specific cytogenetic or morphologic subgroups were generally imprecise. Occupational exposure to extremely low-frequency magnetic fields (EMF) was associated with MDS with a normal karyotype [odds ratio (OR) 2.0, 95% confidence interval (95% CI) 1.0-4.0]. The exposure-response association was consistent for intensity but inconclusive for duration. A decreased risk was observed for MDS, irrespective of karyotypic pattern, among farmers and farmhands (OR 0.53, 95% CI 0.35-0.81). CONCLUSIONS: Cytogenetically abnormal MDS was generally not associated with occupational or hobby exposure to known or suspected genotoxic agents. However, exposure prevalences and intensities were low for several agents. An association was suggested between occupational exposure to EMF and MDS with a normal karyotype. Biases due to differential information quality and selective participation cannot be ruled out.

Case-Control Studies↗
PubMed2002

Prognostically important chromosomal aberrations in soft tissue sarcomas: a report of the Chromosomes and Morphology (CHAMP) Study Group.

Cytogenetic analysis has not only provided important information on the pathogenesis of soft tissue tumors but, by disclosing distinct chromosomal rearrangements in different histopathological entities, has also come to serve as a valuable diagnostic tool. Little is known as yet about the potential prognostic impact of cytogenetic features detected in these tumors. A total of 239 benign and 221 malignant soft tissue tumors with clonal chromosome aberrations were subdivided according to general karyotypic features, such as degree of complexity and ploidy level, and rearrangements of specific chromosomal regions. The cytogenetic variables were analyzed regarding clinical outcome, using time to metastasis as the end point. Selected variables were then compared with established clinicopathological predictors of metastasis development. When the entire material was considered, 167 of 268 investigated cytogenetic variables were associated with clinical outcome. Focusing on the subset of 151 patients with high-grade sarcoma, 17 variables were identified that, besides grade and size, were associated with increased risk of metastasis development. A final Cox regression analysis identified five independent cytogenetic predictors of adverse outcome; breakpoints in chromosome regions 1p1, 1q4, 14q1, and 17q2, and gain of regions 6p1/p2. An increasing effect on metastatic risk was seen with increasing involvement of the selected cytogenetic variables, even when different histopathological types were studied separately. We conclude that cytogenetic data provide independent prognostic information in soft tissue sarcomas. Furthermore, our results point to specific areas of the genome harboring genes that may influence the metastatic potential of sarcoma cells.

Adolescent↗
PubMed2002

Effects of systematic exposure assessment errors in partially ecologic case-control studies.

BACKGROUND: In ecologic studies, group-level rather than individual-level exposure data are used. When using group-level exposure data, established by sufficiently large samples of individual exposure assessments, the bias of the effect estimate due to sampling errors or random assessment errors at the individual-level is generally negligible. In contrast, systematic assessment errors may produce more pronounced errors in the group-level exposure measures, leading to bias in ecologic analyses. METHODS: We focus on effects of systematic exposure assessment errors in partially ecologic case-control studies. Individual-level information on disease status, group membership, and covariates is obtained from registries, whereas the exposure is a group-level measure obtained from an established exposure database. Effects on bias and coverage of 95% CI in various error situations are investigated under the linear risk model, using both simulated and empirical ecologic data on exposures that are binary at the individual level. RESULTS: Our simulations suggest that the bias produced by systematic exposure assessment errors under the linear risk model is generally approximately equal to the ratio of the slope bias and the intercept bias in ordinary linear regression with measurement errors in the independent variable. Consequently, bias in either direction can occur. Exposure assessment errors that systematically distort the group-level exposure measures have more pronounced effects on bias and coverage than errors producing random fluctuations of the group-level measures, which imply bias towards the null. CONCLUSIONS: The results indicate the need for careful consideration of potential effects of systematic distortions of the group-level exposure measures when constructing and applying group-level exposure databases, such as probabilistic job exposure matrices.

Bias↗
PubMed2002

Estimating attributable fraction in partially ecologic case-control studies.

Partially ecologic case-control studies combine group-level exposure data with individual-level data on disease status, group membership, and covariates. If the exposure measure is the exposure prevalence of various groups, the attributable fraction (AF; the estimated proportion of cases that are attributable to exposure) can be estimated by classifying all subjects in groups with exposure prevalence above zero as exposed. Such a threshold AF estimator ([AF]T) is unbiased in confounding-free situations if the threshold is 100% sensitive, but it might be imprecise. We propose an alternative AF estimator, [AF]L, for partially ecologic case-control studies under a linear model for the association between the exposure prevalence and the odds ratio. The proposed estimator can also be applied to situations in which covariate adjustment is necessary. [AF]T and [AF]L are compared with respect to precision and bias. [AF]L is also unbiased when the exposure prevalence is zero in the group(s) assessed as unexposed. Using [AF]L will consistently result in improved precision compared with [AF]T, although the results may not differ substantially. The 95% confidence intervals for both AF estimators show satisfactory coverage in bias-free exposure scenarios. Pronounced negative bias and decreased coverage result for both AF estimators even when small fractions (3-9%) of exposed subjects are included in the group assessed as unexposed.

Bias↗
PubMed2002

Female fertility in relation to the consumption of fish contaminated with persistent organochlorine compounds.

OBJECTIVES: The purpose of the study was to assess the effect of exposure to presistent organochlorine compounds through the consumption of fatty fish from the Baltic Sea on human fertility. METHODS: Information on time to pregnancy, miscarriages, and subfertility was collected retrospectively by self-administered questionnaires in two cohorts of fishermen's sisters from the Swedish east coast, by the Baltic Sea, and the west coast, where fish are less contaminated. Along with cohort affiliation, fish consumption and growing up in a fishing village or fisherman's family were used as measures of exposure within the eastcoast cohort (ie, the exposed cohort). RESULTS: There was no support for a negative effect of the consumption of fatty Baltic Sea fish on time to pregnancy, miscarriages, or subfertility. On the contrary, some evidence pointed towards a protective effect of fatty fish consumption within both cohorts. CONCLUSIONS: No evidence of reduced fertility was found for women who could be assumed to have a high lifetime consumption of fatty fish contaminated by persistent organochlorine compounds. A possible explanation for this finding is that a positive effect of some of the constituents in fatty fish could be strong enough to disguise the hazardous effects of exposure to persistent organochlorine compounds.

Abortion, Spontaneous↗