Search PubMed⌕ Search

Biomedical subjects

A Ahlbom

Publications and source records attributed to A Ahlbom.

At least 73 records · Page 4Linked to original sources
PubMed1996

How to evaluate interaction between causes: a review of practices in cardiovascular epidemiology.

To increase the knowledge of interaction or synergy between risk factors in an important task in medical research. Still, current literature in cardiovascular epidemiology reflects major misconceptions as how to evaluate interaction. This paper presents Rothman's model of causation from which strict empirical criteria of interaction can be derived. In principle, the method to apply consists of comparing risk differences for one risk factor of interest across strata of the other. Commonly used but incorrect approaches are exemplified and discussed. These include reporting risk of disease among those with combined exposure, comparing relative risks for one exposure after stratification by level of the other, and including an interaction term in the regression model and drawing conclusions from its P-value.

Cardiovascular Diseases↗
PubMed1996

Survival and cause-specific mortality in inflammatory bowel disease: a population-based cohort study.

BACKGROUND & AIMS: A population-based cohort study of 1251 subjects with Crohn's disease and 1547 subjects with ulcerative colitis, diagnosed in Stockholm between 1955 and 1984, was performed to examine the survival, changes in survival over time, and cause-specific mortality. METHODS: The cohort of patients was followed up in the National Cause-of-Death register until 1990. National mortality rates were used for comparisons. RESULTS: The observed vs. expected survival rate after 15 years was 93.7% (95% confidence interval [CI], 91.8%-95.7%) for Crohn's disease and 94.2% (95% CI, 92.4%-96.1%) for ulcerative colitis. Overall, 174 deaths occurred vs 115.42 expected (standardized mortality ratio, 1.51; 95% CI, 1.29-1.75) in Crohn's disease. In ulcerative colitis, 255 deaths occurred compared with 186.78 expected (standardized mortality ration, 1.37; 95% CI, 1.20-1.54). Inflammatory bowel disease was the major contributor to the elevated mortality rate, but mortality from colorectal cancer, asthma, and non-alcohol-related liver diseases was increased in ulcerative colitis; mortality from other gastrointestinal diseases was increased in ulcerative colitis as well as in Crohn's disease. CONCLUSIONS: Data in the present study are compatible with the hypothesis that subjects with inflammatory bowel disease have an increased mortality compared with the general population.

Adolescent↗
PubMed1996

Cancer in banana plantation workers in Costa Rica.

BACKGROUND: Costa Rica has population and disease registries with potential value for epidemiological research. Pesticides have been intensively used on banana plantations, for example dibromochloropropane (DBCP). This study was planned to examine the quality of the cancer and civil registries and the feasibility of record linkages, and to explore cancer patterns among a highly exposed group. METHODS: A retrospective cohort study was carried out. Workers on the payrolls of banana companies, as reported to the Social Security System at any time between 1972 and 1979, were followed up in the cancer registry between 1981 and 1992: 29 565 men and 4892 women for 407 468 person-years. The observed cases of cancer were compared to the expected values, derived from the national incidence rates. RESULTS: We identified 368 cancer cases, 292 among men (standardized incidence ratio [SIR] = 76, 95% confidence interval [CI] 67-84) and 76 among women (SIR = 116, 95% CI: 90-142). Among men increased SIR were observed for melanoma (SIR = 197, 95% CI: 94-362) and penile cancer (SIR = 149, 95% CI: 55-324); among women for cervix cancer (SIR = 182, 95% CI: 122-241) and leukaemia (SIR = 274, 95% CI: 86-639). Risk estimates for lung cancer were evaluated among male workers with the longest time of employment. CONCLUSIONS: Follow-up was difficult due to deficient identification variables in the cancer registry and to easier identification of the living compared to the decreased in the civil registry at the end of the observation period. The various systematic errors in this study are likely to produce an underestimation of the relative risk estimates. This study contributes to improvements of the registries and increases the potential for cancer epidemiology in Costa Rica and other developing countries.

Adult↗
PubMed1996

Estimating exposure in studies of residential magnetic fields and cancer: importance of short-term variability, time interval between diagnosis and measurement, and distance to power line.

Validity of exposure assessment methods has been a major concern in epidemiologic studies of magnetic field exposure and cancer. We conducted a study to evaluate the relative importance of distance to power lines and calculated historical magnetic fields when estimating past magnetic field exposure. Another goal was to compare results based on various estimates of magnetic field exposure, to assess the importance of short-term variability in magnetic fields, time between diagnosis and measurement, and sources of magnetic field exposure. We used data from a Swedish case-control study of residential exposure to magnetic fields and cancer. Childhood leukemia risk was associated with calculated historical annual average magnetic fields regardless of distance, and the association with distance disappeared when both variables were entered into the same logistic regression model. Relative risks for measurements at the time of the study (contemporary annual average fields, spot calculations, and spot measurements) were all close to or below unity. The results support the hypothesis that the difference between results using historical calculations and spot measurements is explained by the time interval between diagnosis and contemporary magnetic field estimates.

Adolescent↗
PubMed1996

Glioma and occupational exposure in Sweden, a case-control study.

OBJECTIVES: The aim of the study was to analyse whether any job titles, industrial codes, and certain occupational exposures were associated with an increased risk of glioma. METHODS: A population based case-control study of incident primary brain tumours in adults was carried out in Uppsala, Sweden in the period 1987-90. The study included 192 cases of glioma and 192 matched controls. It also included cases with other tumours of the central nervous system with matched controls. Information from all 343 controls was used in this study. Information was collected by means of a questionnaire that was sent to all subjects. An occupational hygienist reviewed the questionnaires for self reported exposures to substances and assessed whether these reported exposures were plausible or not in the corresponding occupation. RESULTS: The kappa coefficient for those classified by the two methods ranged between 0.46 and 0.88, and they were almost the same for cases and controls. For men exposed to solvents a relative risk (RR) of 2.6 (95% CI 1.3 to 5.2) was found. For men exposed to pesticides the RR was 1.8 (95% CI 0.6 to 5.1), and for plastic materials the RR was 3.6 (95% CI 1.0 to 12.4). For men employed in forestry and logging the RR was 2.2 (95% CI 0.9 to 5.3) and in basic metal industries 2.0 (95% CI 1.0 to 4.0). CONCLUSION: An increased risk of glioma was associated with use of solvents, pesticides, and plastic materials but this should be interpreted with some caution.

Adult↗
PubMed1995

Effect of twinship on incidence of cancer of the testis, breast, and other sites (Sweden).

It has been suggested that cancers of the testis and breast are associated with exposure to estrogens and other hormones in utero. Twin pregnancies have higher levels of pregnancy-associated hormones than singleton pregnancies, and these levels may be higher in dizygotic than in monozygotic twin pregnancies. Through a large population-based study of twins, we assessed the hypothesis that levels of pregnancy-associated hormones have etiologic importance for cancers of the testis, breast, and other sites. The incidence of all cancers among 46,767 members of the Swedish Twin Registry was compared with the incidence among the Swedish general population. We found testicular cancer excess among dizygotic twins (observed/expected[O/E ratio = 2.3, CI = 1.1-4.2) compared with older men (O/E ratio = 1.2, CI = 0.5-2.4). In addition, a substantially elevated incidence of breast cancer was observed in dizygotic twin women aged 20 to 29 years (O/E = 6.7, CI = 2.9-13.1). None of the other age or zygosity groups showed notable elevations in incidence of testicular, breast, or other cancers. We conclude that dizygotic twinship may be associated with cancer of the breast and testis among young adults. These findings support the concept that pregnancy hormones are associated with risk of testicular and breast cancer, although non-hormonal aspects of twin pregnancy that vary with respect to zygosity cannot be excluded as explanatory factors.

Adult↗
PubMed1995

Magnetic fields and childhood cancer--a pooled analysis of two Scandinavian studies.

To test the hypothesis that exposure to magnetic fields, of the type generated by high voltage installations, increases cancer incidence in children, the original data from two case-control studies were pooled. The Swedish study was based on children living within 300 m from transmission lines, and the Danish study on the total population of Denmark. In both these studies, national cancer registries were used to identify cases of leukaemia, lymphoma or central nervous system tumour. Controls were selected randomly from the study populations. Magnetic field exposure was assessed through theoretical calculations of the magnetic fields before the time of diagnosis. An elevated relative risk of childhood leukaemia was found for calculated magnetic field levels of > or = 0.2 microT, estimated at 2.0 (95% CI 1.0-4.1), and for magnetic field levels of > or = 0.5 microT, estimated at 5.1 (95% CI 2.1-12.6). The results support the hypothesis of an association between magnetic fields and childhood leukaemia.

Adolescent↗
PubMed1995

Total hip replacement and cancer. A cohort study.

The incidence of cancer after hip replacement was studied in the 1.6 million inhabitants of Stockholm County, Sweden. A cohort of 10,785 individuals who had had hip replacement between 1974 and 1988 was followed from the date of operation to the first malignant tumour, to death, or to the end of 1989. The follow-up was based on 58,437 person-years at risk as calculated from information obtained by record-linkage with the National Cancer Registry and the National Cause-of-Death Register. The Standardised Morbidity Ratio (SMR) for all cancer sites, disregarding the length of follow-up, was 0.96 (95% CI 0.90 to 1.03). For lymphoma and leukaemia the corresponding SMR was 0.89 (0.68 to 1.14). Our results do not support previous suggestions of an increased incidence of leukaemia and lymphoma after total hip replacement.

Adult↗
PubMed1994

Crohn's disease and cancer: a population-based cohort study.

BACKGROUND/AIMS: To study the association between Crohn's disease and cancer, we performed a population-based study of 1251 subjects with Crohn's disease diagnosed in Stockholm from 1955 to 1984 and followed in both the National Cancer Register and the National Cause-of-Death Register until 1989. METHODS: For comparisons, regional cancer incidence rates in Stockholm County were used together with individually computed person-years at risk in the Crohn's disease cohort. RESULTS: Overall, 69 malignancies occurred among 67 individuals as compared with 59.80 expected malignancies (standardized morbidity ratio [SMR] = 1.15; 95% confidence interval, 0.90-1.46). An excess number of cancers of the upper gastrointestinal tract (SMR, 3.05; 95% confidence interval, 1.67-5.11) was observed, mainly because of an increased number of cancers of the small intestine (SMR, 15.64; 95% confidence interval, 4.26-40.06). An increased occurrence of urinary bladder cancer was also observed (SMR, 2.68; 95% confidence interval, 1.08-5.53). CONCLUSIONS: The occurrence of colorectal cancer was not increased.

Adolescent↗
PubMed1994

Magnetic fields, leukemia, and central nervous system tumors in Swedish adults residing near high-voltage power lines.

We conducted a case-control study to test the hypothesis that exposure to magnetic fields of the type generated by high-voltage power lines increases the incidence of leukemia and central nervous system tumors in adults. The study was based on people who, between 1960 and 1985, had lived on a property in Sweden located within 300 meters of 220 or 400 kilovolt power lines. We identified a total of 325 leukemia cases and 223 cases of central nervous system tumor. Two matched controls per case were selected at random. We assessed exposure by spot measurements and by calculations of the magnetic fields generated by the power lines. For calculated magnetic field levels of 0.2 microT or more closest in time to diagnosis, we found an elevated relative risk (RR) for acute myeloid leukemia [RR = 1.7; 95% confidence interval (CI) = 0.8-3.5] and chronic myeloid leukemia [RR = 1.7; 95% CI = 0.7-3.8]. Using cumulative exposure for the 15 years preceding diagnosis, we found relative risk estimates for acute and chronic myeloid leukemia of 2.3 (95% CI = 1.0-4.6) and 2.1 (95% CI = 0.9-4.7), respectively, for the highest exposure category. For chronic lymphatic leukemia and for central nervous system tumors, relative risk estimates were close to or below unity.

Adult↗
PubMed1993

Magnetic fields and cancer in children residing near Swedish high-voltage power lines.

A case-control study was conducted to test the hypothesis that exposure to magnetic fields of the type generated by high-voltage power lines increases cancer incidence in children. The study base consisted of everyone under age 16 years who had lived on a property located within 300 meters of any of the 220 and 400 kV power lines in Sweden during the period 1960-1985. Subjects were followed from their entry into the study base through 1985. A total of 142 cancer cases were identified through a record linkage to the Swedish Cancer Registry. There were 39 leukemia and 33 central nervous system tumor cases. A total of 558 controls were selected at random from the study base. Exposure was assessed by spot measurements and by calculations of the magnetic fields generated by the power lines, taking distance, line configuration, and load into account. Information about historical loads on the power lines was used to calculate the magnetic fields for the year closest in time to diagnosis. When historical calculations were used as exposure assessment for childhood leukemia with cutoff points at 0.1 and 0.2 microtesla (microT), the estimated relative risk increased over the two exposure levels and was estimated at 2.7 (95% confidence interval (CI) 1.0-6.3) for 0.2 microT and over; p for trend = 0.02. When the upper cutoff point was shifted to 0.3 microT, the relative risk was 3.8 (95% CI 1.4-9.3); p for trend = 0.005. These results persisted when adjustment for potential confounding factors was made. For central nervous system tumor, lymphoma, and all childhood cancers combined, there was no support for an association.

Adolescent↗
PubMed1993

Risk factors for late-onset Alzheimer's disease: a population-based, case-control study.

Our current knowledge of risk factors for Alzheimer's disease is limited and primarily addresses early-onset disease. This study aimed to determine the risk factors for late-onset Alzheimer's disease using a case-control approach. Ninety-eight cases and 216 controls were gathered from an ongoing population survey on aging and dementia in Stockholm (the Kungsholmen Project). We found a high relative risk (3.2; 95% confidence interval, 1.8-5.7) with the presence of at least one first-degree relative affected by dementia. Among all the other risk factors, alcohol abuse (relative risk, 4.4; 95% confidence interval, 1.4-13.8) and manual work (relative risk for men of 5.3; 95% confidence interval, 1.1-25.5) emerged as positively associated. No clear association was found with a family history of Parkinson disease, advanced parental age at index delivery, season of birth, or previous head trauma. In conclusion, our data suggest that the main risk factor for late-onset Alzheimer's disease is a family history of dementia, as has been previously reported for early-onset disease. Moreover, alcohol abuse and occupational exposure might play a specific role for this form of the disease.

Age Factors↗