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Biomedical subjects

U Strömberg

Publications and source records attributed to U Strömberg.

At least 19 recordsLinked to original sources
PubMed1998

Cancer predictive value of cytogenetic markers used in occupational health surveillance programs: a report from an ongoing study by the European Study Group on Cytogenetic Biomarkers and Health.

The cytogenetic endpoints in peripheral blood lymphocytes: chromosomal aberrations (CA), sister chromatid exchange (SCE) and micronuclei (MN) are established biomarkers of exposure for mutagens or carcinogens in the work environment. However, it is not clear whether these biomarkers also may serve as biomarkers for genotoxic effects which will result in an enhanced cancer risk. In order to assess this problem, Nordic and Italian cohorts were established, and preliminary results from these two studies indicated a predictive value of CA frequency for cancer risk, whereas no such associations were observed for SCE or MN. A collaborative study between the Nordic and Italian research groups, will enable a more thorough evaluation of the cancer predictivity of the cytogenetic endpoints. We here report on the establishment of a joint data base comprising 5271 subjects, examined 1965-1988 for at least one cytogenetic biomarker. Totally, 3540 subjects had been examined for CA, 2702 for SCE and 1496 for MN. These cohorts have been followed-up with respect to subsequent cancer mortality or cancer incidence, and the expected values have been calculated from rates derived from the general populations in each country. Stratified cohort analyses will be performed with respect to the levels of the cytogenetic biomarkers. The importance of potential effect modifiers such as gender, age at test, and time since test, will be evaluated using Poisson regression models. The remaining two potential effect modifiers, occupational exposures and smoking, will be assessed in a case-referent study within the study base.

Biomarkers, Tumor↗
PubMed1998

Chromosomal aberrations in lymphocytes predict human cancer: a report from the European Study Group on Cytogenetic Biomarkers and Health (ESCH).

Chromosomal aberrations (CAs), sister chromatid exchanges (SCEs), and micronuclei (MN) in peripheral blood lymphocytes have for decades been used as cytogenetic biomarkers to survey genotoxic risks in the work environment. The conceptual basis for this application has been the idea that increased cytogenetic damage reflects an enhanced cancer risk. Nordic and Italian cohorts have been established to evaluate this hypothesis, and analyses presented previously have shown a positive trend between CA frequency and increased cancer risk. We now report on a pooled analysis of updated data for 3541 subjects examined for CAs, 2703 for SCEs, and 1496 for MN. To standardize for interlaboratory variation, the results for the various cytogenetic end points were trichotomized on the basis of the absolute value distribution within each laboratory as "low" (1-33 percentile), "medium" (34-66 percentile), or "high" (67-100 percentile). In the Nordic cohort, there was an elevated standardized incidence ratio (SMR) for all cancer among subjects with high CA frequency [1.53; 95% confidence interval (CI), 1.13-2.05] but not for those with medium or low CA frequency. In the Italian cohort, a SMR in cancer of 2.01 (95% CI, 1.35-2.89) was obtained for those with a high CA frequency level, whereas the SMRs for those with medium or low did not noticeably differ from unity. Cox's proportional hazards models gave no evidence that the effect of CAs on total cancer incidence/mortality was modified by gender, age at test, or time since test. No association was seen between the SCEs or the MN frequencies and subsequent cancer incidence/mortality. The present study further supports our previous observation on the cancer predictivity of the CA biomarker, which seems to be independent of age at test, gender, and time since test. The risk patterns were similar within each national cohort. This result suggests that the frequency of CAs in peripheral blood lymphocytes is a relevant biomarker for cancer risk in humans, reflecting either early biological effects of genotoxic carcinogens or individual cancer susceptibility.

Chromosome Aberrations↗
PubMed1998

Polychlorinated biphenyls in blood plasma among Swedish female fish consumers in relation to low birth weight.

The authors examined the hypothesized association between the body burden of polychlorinated biphenyls (PCB) in women and the risk of low birth weight for their infants. In Sweden, a main exposure route for PCBs and other persistent organochlorine compounds is through the consumption of fatty fish from the Baltic Sea (on the Swedish east coast). A previous comparison between a cohort of consumers of large quantities of fish from the Swedish east coast and a reference population, together with a following analysis based on questionnaire data from a case-control study within the east coast cohort, supported the hypothesized association. In 1995, blood samples were collected from the wives and ex-wives of fishermen from the Swedish east coast (n = 192) who had given birth during the period 1973-1991. Cases (n = 57), i.e., infants with low birth weight (1,500-2,750 g), were matched with controls (n = 135; birth weight, 3,250-4,500 g) on gender, parity, and calendar year of birth. The concentration of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) in plasma was analyzed; it has been suggested that CB-153 is a relevant biomarker of exposure to PCBs. The concentration of CB-153 in the plasma of mothers during the year of childbirth was "estimated" using some alternative plausible kinetic models. For two alternative estimated exposure datasets, which were focused on separately, an increase in the risk of a low birth weight was observed at a CB-153 concentration of 300 and 400 ng/g lipid weight, respectively (adjusted odds ratios of 2.1 (95% confidence interval (CI) 1.0-4.7) and 2.3 (95% CI 0.9-5.9)). The present results strengthen the findings reported previously for this study population.

Adolescent↗
PubMed1998

Agreement between reported fish consumption obtained by two interviews and its impact on the results in a reproduction study.

In an ongoing study of the hypothesised association between consumption of fish contaminated with persistent organochlorine compounds and low birth weight, a relevant measure of exposure is the accumulated fish consumption over long time periods. An issue of concern in this study is the quality of the retrospective exposure assessments. The present investigation was undertaken to determine the agreement between reported fish consumption in two interviews with approximately one year in between. in order to evaluate its impact on the effect estimates. The agreement decreased with increasing retrospective time interval between interview and focused time period of fish consumption. Furthermore, the exposure assessments based on the two interviews led to considerably different effect estimates.

Adult↗
PubMed1998

Absence attributed to incapacity and occupational disease/accidents among female and male workers in the fish-processing industry.

Sick-leave between 1984 and 1989 was higher among both female (n = 515) and male (n = 304) fish-processing workers [observed/expected (O/E) 2.24 and 1.69, respectively] than among non-exposed groups (0.62 and 0.89). Diagnoses in the musculoskeletal system dominated (i.e., neck/upper limbs; females, exposed vs. non-exposed workers: 30 vs. 12%; males: 11 vs. 5.8%). In subjects who left employment, the O/E-ratio decreased (females: 3.02 vs. 1.55; males: 2.40 vs. 1.55). Among those women hired before the start of the observation period, exposed subjects had higher frequencies of sick-leave than non-exposed, for both total illness and musculoskeletal diagnoses. In the men, there were corresponding differences, though not fully statistically significant. Reported occupational diseases [O/E: females: 4.5; (95% confidence interval) CI = 3.2-6.1; males: 2.3; CI = 1.3-3.9] and accidents (females: 4.3; CI = 3.0-5.9; males: 1.8; CI = 1.2-2.7) were also higher in female than in male fish-processing workers, and much higher than in non-exposed workers. In conclusion, work in the fish-processing industry was associated with increased frequencies of sick-leave, especially because of diagnoses of the musculoskeletal system, and occupational disorders and accidents, in particular among female workers.

Accidents, Occupational↗
PubMed1998

Lead concentrations in tibial and calcaneal bone in relation to the history of occupational lead exposure.

OBJECTIVES: This study tested a simple model of the relationship between the lead concentration in bone (bone-Pb), exposure time, and lead in plasma (P-Pb) and whole blood (B-Pb) to make it possible to use bone-Pb as a retrospective exposure index. METHODS: Seventy-seven active lead workers and 24 referents were studied. The bone-Pb in tibia (T-Pb) and calcaneus (C-Pb) was measured by in vivo X-ray fluorescence. P-Pb was calculated from B-Pb by use of the nonlinear relationship between these variables. Cumulative B-Pb (cumB-Pb) and P-Pb (cumP-Pb) were calculated to the time of the bone-Pb measurements. In addition, cumP-Pb was adjusted by applying varying rate constants for the transfer of lead from bone to plasma. RESULTS: There were close linear associations between the lead concentrations in tibia (proportion of variance explained, R2 = 0.78) and calcaneus (R2 = 0.80), on one hand and the cumB-Pb on the other. The best fit of bone-Pb to the adjusted cumP-Pb (0.79 for T-Pb; 0.82 for C-Pb) was obtained for the terminal phase half-times of 13 and 12 years, respectively. CONCLUSIONS: The combined data on bone-Pb and exposure time make it possible to estimate previous mean P-Pb and B-Pb. Such estimates will be valuable in studies of toxic effects on long-term exposed lead workers when data on the intensity of previous exposure are lacking. The use of P-Pb in modeling bone-Pb kinetics is physiologically relevant, but the use of adjusted cumP-Pb, as compared with cumB-Pb, did not significantly change the variance in the relation to bone-Pb.

Adolescent↗
PubMed1997

The impact of age, lactation and dietary habits on PCB in plasma in Swedish women.

The mean concentration of the chlorinated biphenyl 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) in plasma from 192 fishermen's wives from the Swedish east coast was on a fresh weight basis 960 (range 80-4300) pg/g and lipid adjusted 160 (range 20-780) ng/g lipid. The concentration of CB-153 in plasma was significantly influenced by age, total lactation time and place of living during childhood and adolescence (fishing village vs. other place). The residential variable probably reflects early life consumption of fish from the Baltic Sea (at the Swedish east coast) contaminated with persistent organochlorine compounds.

Adult↗
PubMed1997

A method for deciding early stopping of inconclusive case-control studies in settings where data are stratified.

Statistical methodology for early stopping of clinical trials is well developed. However, in epidemiologic studies, methods for deciding early stopping have rarely been considered. In contrast to clinical trials, termination due to an early significant result is indeed seldom relevant, because further expenditure is then likely to be worthwhile in order to obtain a more precise effect estimate and to more precisely account for confounders. On the other hand, if data obtained early indicate an inconclusive final result and if continuation of the epidemiologic study is expensive, then it might be desirable to stop the study early. The present paper proposes a method for evaluating the possibility that an ongoing case-control study will produce an inconclusive final result. The method is developed for stratified case-control data. In principle, probable final results, given the available data, are predicted by repeatedly simulating the remaining data using plausible assumptions on the true exposure effect. These assumptions involve the current effect estimate as well as some alternatives, chosen with respect to the investigator's prior hypothesis concerning a harmful exposure effect, which are in reasonable agreement with the available data.

Animals↗
PubMed1997

Monitoring of polychlorinated biphenyls in human blood plasma: methodological developments and influence of age, lactation, and fish consumption.

Human plasma samples from 50 wives of fishermen have been analyzed with respect to PCBs. The non-ortho-substituted PCB congeners CB-126 and CB-169 were determined by mass spectrometry in negative ion chemical ionization mode, which demonstrated a limit of detection of 30 fg. The recoveries of the internal standards used for determination of ortho-substituted CBs were approximately 95%. Two methods, one gravimetric and the other based on enzymatic determinations of triglycerides, cholesterol and phospholipids, were compared for the determination of total amount of lipids in the plasma samples; the correlation coefficient was 0.82 and the slope 0.98. For practical reasons, enzymatic determinations are recommended for further use. The total, lipid-adjusted concentrations of PCBs in plasma were influenced by age, total lactation time and consumption of fatty fish from the Baltic Sea.

Adult↗
PubMed1996

Collapsing ordered outcome categories: a note of concern.

When analyzing and interpreting data from an epidemiologic study where ordinal (ordered categorical) outcomes have been measured in different exposure groups, an effect parameter of interest is the common odds ratio implied by the proportional odds model. This model can sometimes be applied to a collapsed outcome variable, instead of the measured variable, without reducing efficiency considerably. However, in a given data set, changing the outcome categories can affect the effect estimate as well as the inference being drawn from the data, even if the true effect itself has not changed. In particular, one should be careful in dichotomizing the measured outcome variable.

Bias↗
PubMed1996

Cancer incidence and specific occupational exposures in the Swedish leather tanning industry: a cohort based case-control study.

OBJECTIVE: To study the effect on the incidence of cancer of exposure to chemicals handled in the leather tanning industry. MATERIALS AND METHODS: A case-control study was performed within a cohort of 2487 workers employed for at least six months during the period 1900-89 in three Swedish leather tanneries. 68 cancer cases (lung, stomach, bladder, kidney, nasal, and pancreatic cancers and soft tissue sarcomas) and 178 matched controls were studied. Effects of chemical exposures on cancer incidence, adjusted for age at risk, sex, and plant were estimated with a conditional logistic regression model. RESULTS: A significant association was found between exposure to leather dust and pancreatic cancer (odds ratio (OR) 7.19, 95% confidence interval (95% CI) 1.44 to 35-89). An association was indicated between leather dust from vegetable tanning and lung cancer. After adjustment for smoking habits a tentative association between organic solvents and lung cancer lost its significance. No association was found between exposure to chlorophenols and soft tissue sarcomas. CONCLUSIONS: The significant association between leather tanning and soft tissue sarcomas that was found in our previous cohort analysis could not be explained by exposure to chlorophenols. On the other hand a significant association was found between exposure to leather dust and pancreatic cancer, and exposure to leather dust from vegetable tanning was often present in cases with lung cancer. Due to the small numbers of cases, the results can, however, only lead to tentative conclusions.

Adult↗
PubMed1996

Dietary intake of fish contaminated with persistent organochlorine compounds in relation to low birthweight.

OBJECTIVES: The purpose of this study was to assess the hypothesized association between persistent organochlorine compounds through the consumption of fatty fish from the Baltic Sea (at the Swedish east coast) and low birthweight. MATERIALS AND METHODS: During the period 1973-1991, 72 cases of low birthweight (1500-2750 g) were selected from among infants born to fishermen's wives within a cohort from the Swedish east coast. For each case two referents were selected. The mothers were interviewed about their dietary and smoking habits and place of living during childhood and adolescence. RESULTS: A high total current intake of fish from the Baltic Sea (> or = 4 meals per month) tended to increase the risk of having an infant with low birthweight [adjusted odds ratio (OR) 1.9, 95% confidence interval (95% CI) 0.9-3.9]. The effect was more conspicuous for the boys (OR 3.4, 95% CI 1.1-11). No such effects were observed when the estimated intake of fish was considered for the period in which the infant was born. However, mothers who had grown up in a fishing village had an increased risk of having an infant with low birthweight (OR 2.1, 95% CI 1.0-4.3). CONCLUSIONS: The variable "grown up in a fishing village" can be interpreted as an indirect measure of a mother's accumulated consumption of fish from the Baltic Sea. This idea supports an association between a high consumption of contaminated fish from the Baltic Sea and an increased risk for low birthweight. The effect estimates based on the mothers' reported fish consumptions were dependent on the period under consideration and therefore were somewhat ambiguous.

Adult↗
PubMed1995

Adjustment of a sparse and irregular reference rate matrix.

Regional sex-specific rates of a rare disease often show conspicuous fluctuations over conventional strata of age and calendar time. In a cohort study, when such rates are used as references in the calculation of the expected number of cases, the accumulated person-time of the study cohort may somewhat haphazardly contribute to the result. For example, only the person-time observed in the strata with at least one reference case registered contributes to the expected number of cases. It may therefore be important to evaluate whether the regional rates seem to differ systematically from the more stable national rates. When such differences may be indicated, a fairly simple method is proposed for smoothing rates. This method aims to produce rates that better reflect the underlying, supposedly smooth, rate pattern over age and calendar time in a population of interest. The present paper illustrates the technique by considering right-sided colon cancer incidence rates from a regional male population, which the authors use to calculate the expected number of such cases in an occupational cohort.

Cohort Studies↗
PubMed1995

Radiological changes in asbestos cement workers.

OBJECTIVE: To explore associations between exposure to asbestos cement dust and radiographic findings in lung parenchyma and pleura. METHODS: Radiographs from 174 blue collar workers and 29 white collar workers from an asbestos cement plant formed one part of the study. Progression of small opacities was further studied in those 124 blue collar workers, for whom two radiographs taken after the end of employment were available. The median readings from five readers who used the full ILO 1980 classification were used. As exposure indices, time since start of employment, duration of employment, cumulative exposure, and average intensity of asbestos exposure were used. The influence of age and smoking was also considered in multiple logistic regression analyses. RESULTS: Small opacities (profusion > or = 1/0) were closely correlated with time related exposure variables, and showed weaker association with intensity based exposure variables. The odds ratio (OR) for small opacities was equal to 2.8 (90% CI 1.2, 6.7) in the > 30 f(fibre)-y/ml group, compared with those in the 0-10 f-y/ml group. Progression of at least two minor ILO categories after the end of employment was seen in 20%. Also, pleural thickening was closely related to time. By contrast, costophrenic angle obliterations were not associated with the time related variables, but closely associated with the intensity of asbestos exposure, and tended to occur during employment. The OR was 4.5 (90% CI 1.3, 15) in the > 2 f/ml group, compared with those in the 0-1 f/ml group. CONCLUSIONS: In these workers, exposed mainly to chrysotile but also to small amounts of amphibole, the risk of radiographically visible parenchymal abnormality was substantially increased and strongly dependent on time related exposure variables. Progression was found long after the end of exposure. The findings on costophrenic angle obliterations, supposed to be sequelae of benign pleural effusions, were consistent with an immediate reaction triggered by intense asbestos exposure.

Adult↗
PubMed1995

Substantial decrease of blood lead in Swedish children, 1978-94, associated with petrol lead.

OBJECTIVES: To study the potential impact of environmental exposure to petrol lead, residential area, age, sex, and lead exposing hobby, on blood lead concentrations (BPb) in children. METHODS: In the south of Sweden, yearly from 1978-94, BPb was measured in 1230 boys and 1211 girls, aged between 3 and 19 (median 10; quartiles 9 and 12) years. RESULTS: For the samples of 1978, the geometric mean (GM) was 67 (range 30-250) micrograms/l in boys and 53 (18-161) micrograms/l in girls, whereas the corresponding GMs for 1994 were 27 (12-122) and 23 (12-97) micrograms/l. The sex difference was present only in children over eight. Moreover, residential area affected BPb; in particular, children living near a smelter area had raised BPbs. There was a clear ecological relation between BPb (adjusted GM) and annual lead quantity in petrol sold in Sweden, which was estimated to be 1637 tonnes in 1976 and 133 tonnes in 1993 (P < 0.001, ecological linear regression analysis, where a two year lag of petrol lead was applied). In the 171 boys and 165 girls who were sampled twice with an interval of one to four years, the decreases in BPb were estimated to be 6% (95% confidence interval 4%-8%) and 10% (8%-13%)/year, respectively. CONCLUSIONS: The present report points out the considerable beneficial effect of the gradual banning of petrol lead on the lead exposure affecting the population and differential sex specific BPb patterns due to a pronounced age effect in girls, which may be caused by older girls' lower food intake per kg of body weight, lower lung ventilation, cleaner life style, and loss of blood lead through menstrual bleedings.

Adolescent↗
PubMed1995

Mortality and cancer incidence among Swedish fishermen with a high dietary intake of persistent organochlorine compounds.

OBJECTIVES: The objective of this study was to determine mortality and cancer incidence in two cohorts of Swedish fishermen with different dietary intakes of persistent organochlorine compounds. METHODS: The following two cohorts of Swedish fishermen were established: a cohort of 2896 subjects from the Swedish east coast (on the Baltic Sea), and a cohort of 8477 subjects from the Swedish west coast. Mortality and cancer incidence were studied in these cohorts and comparisons were made both with the regional populations and between the cohorts. RESULTS: The incidences of stomach and squamous cell skin cancers among the eastcoast fishermen were elevated as compared with those of the regional population [standardized incidence ratio (SIR 1.6, 95% confidence interval (95% CI) 1.0-2.4 and SIR 2.3, 95% CI 1.5-3.5 respectively] and with the westcoast cohort (IRR 2.2, 95% CI 1.3-3.5 and IRR 1.9, 95% CI 1.2-3.1, respectively), while that of colon cancer was decreased. Moreover, mortality from multiple myelomas was increased among the eastcoast fishermen as compared with that of the general population [standardized mortality ratio (SMR) 3.1, 95% CI 1.2-6.4) and the westcoast fishermen (IRR 3.2, 95% CI 1.2-8.7). A 12% decreased mortality in ischemic heart disease was found for the eastcoast cohort. A slight, but significant increase in such deaths was noted among the westcoast fishermen. CONCLUSIONS: High consumers of fatty fish, contaminated with organochlorine compounds, had an increased risk for stomach and skin cancer. They also had a suggestive decrease in mortality from ischemic heart diseases.

Animals↗