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Biomedical subjects

A Ahlbom

Publications and source records attributed to A Ahlbom.

At least 109 records · Page 6Linked to original sources
PubMed1991

Prevalence of Alzheimer's disease and other dementias in an elderly urban population: relationship with age, sex, and education.

We studied the prevalence of different types of dementia in an elderly population in Stockholm, Sweden, in relation to age, sex, and education. The study confirmed Alzheimer's disease (AD) as the most frequent type of dementia and the positive association of dementias with age, even in the most advanced ages. In contrast to previously reported data, we found the same proportion of AD and vascular dementia in the different age strata, and no sex differences regarding the prevalence of different dementia types. Finally, less educated people had a higher prevalence of all dementias, due essentially to a higher prevalence of alcoholic dementia and unspecified type of dementia. The prevalence of AD was similar across different levels of education.

Age Factors↗
PubMed1990

Prenatal X-ray exposure and childhood cancer in Swedish twins.

The association between X-ray exposure in utero and childhood cancer was studied in a case-control study, nested in a national cohort of Swedish twin births. Records of the Swedish Twin Register for those born 1936-1967 (n = 83,316) were linked to the Swedish Cancer Register (1958-1983) and the Swedish Cause-of-Death Register (1952-1983). Ninety-five cases of childhood cancer before the age of 16 were identified. Two controls from the Twin Register were matched to each case by sex and year of birth. Maternal X-rays during pregnancy were documented for 41% of the cases and 36% of the controls. The crude relative risk of any childhood cancer associated with any prenatal X-ray was 1.2 (95% CI; 0.7-2.1). For the cases 64% of the X-rayed women had had abdominal X-rays, the numbers for the controls were 57%. Fifty-nine per cent of the X-rayed women had had abdominal X-rays, which were associated with a relative risk for all cancers of 1.4 (Cl; 0.8-2.5), leukemias 1.7 (Cl; 0.7-4.1) and tumors of the central nervous system 1.5 (Cl; 0.5-4.2). There was no apparent confounding by mother's age, drug use, obstetric complications, previous miscarriages, social class or length of pregnancy. The observed relative risks of cancer following prenatal X-ray exposure are consistent with previous studies, suggesting that the developing fetus may be more sensitive to the carcinogenic effects of ionizing radiation than are children irradiated post-natally.

Adolescent↗
PubMed1990

Retrospective versus original information on diet: implications for epidemiological studies.

The aim of this study was to evaluate the use of retrospective information on diet in relation to the information originally reported. Hospital controls (n = 131) who participated in a case-control study on diet and pancreatic cancer in Stockholm, Sweden, answered a second postal questionnaire four years later about their current and previous food consumption. The food consumption was dichotomized for the purpose of the analysis. In relation to the original information, the use of retrospective information overestimated previous food consumption among subjects with increased intake, while retrospective information underestimated previous food consumption among subjects with decreased intake. These tendencies were slightly more pronounced in the age group 60-79 years than in the age group 40-59 years. For subjects with unchanged food consumption, there was a high agreement between original and retrospective information. Considerable differential misclassification could be introduced in an epidemiological study if cases and non-cases differ with regard to changes in food consumption.

Adult↗
PubMed1990

Is brain cancer mortality increasing in industrial countries?

This paper analyzes recent age-specific trends in brain and other central nervous system cancer mortality from 1968 to 1986-1987 in the United States, United Kingdom, Italy, France, and West Germany. It also examines changes in the use of diagnostic confirmation technology in the U.S. SEER program from 1973 to 1987 to estimate the influence of such factors on recent mortality trends. Other sources of error have not been evaluated in this paper. In the United States and Sweden, deaths due to brain and other central nervous system cancer, adjusted to the overall population, are unchanging. However, age-specific analyses of brain and other nervous system cancer in six major industrial countries show markedly different trends at different age groups, with drastic increases in brain tumor rates in the old: rates doubled in persons ages 75 to 84. In the United States, microscopic or radiographic confirmation occurred throughout this time period in 96% of all incident cases of brain and other central nervous system cancers diagnosed before death in the SEER program, with older persons receiving consistently more radiographic tests than younger persons. The use of diagnostic technology may change over time and across populations, but it is not known to what extent it accounts for these increasing trends, which require careful additional study.

Adolescent↗
PubMed1990

Inflammatory bowel disease and tobacco smoke--a case-control study.

A case-control study was carried out in Stockholm, Sweden between 1984 and 1987 to evaluate the association of cigarette smoking and exposure to environmental tobacco smoke during childhood and the subsequent development of inflammatory bowel disease. Information on smoking was obtained by a postal questionnaire. The relative risk of Crohn's disease in current smokers compared with those who had never smoked was 1.33 (95% confidence limits 0.7; 2.6) in men and 4.99 (2.7; 9.2) in women; the corresponding results for ulcerative colitis were 0.96 (0.5; 1.8) and 0.72 (0.4; 1.4). The relative risk of ulcerative colitis in recent exsmokers compared with those who had never smoked was 2.18 (0.9; 5.0). Furthermore, an increase in the risk of Crohn's disease was found in those who were exposed to environmental tobacco smoke during childhood, the relative risk being 1.50 (1.0; 2.3). The corresponding relative risk of ulcerative colitis was 0.98 (0.6; 1.5).

Adult↗
PubMed1990

Interpretation of "negative" studies in occupational epidemiology.

Two criteria for an interpretation of noneffect are that the relative risk estimate be near unity and that the confidence interval be narrow; lack of statistical significance has no bearing on this issue. A further requirement is that the relative risk estimate not be near the null value as an effect of non-differential exposure misclassification, negative confounding, or some other systematic error. Occasionally, when results are unexpected or difficult to accept, studies are "underinterpreted" as negative or inconclusive on the basis of arguments such as "confounding," "crude exposure assessment," or "lack of a known mechanism." The present paper supports the position that these arguments are commonly invalid. Scientific standards should be used to separate causal associations from noncausal ones, but in public health decisions this practice has to be balanced by the principle that the "benefit of the doubt" should be given to the persons subject to potential risk.

Bias↗
PubMed1988

A review of the epidemiologic literature on magnetic fields and cancer.

Since 1979 several studies have been published that suggest that residential exposure to electromagnetic fields could increase the risk of childhood cancer. Such studies have also been published for adults. In addition there are several studies suggesting that people in "electrical" occupations are at an increased risk of cancer. The objective of this review was to determine whether the role of electromagnetic fields in the origin of cancer can be established from the epidemiologic literature. Several of the studies suffer from methodological or other shortcomings, but it is not clear whether these problems are likely to explain the results. No conclusion can be drawn about the role of electromagnetic fields in the origin of cancer on the basis of current data. The existing literature, however, strongly suggests that research in this area should be pursued.

Adult↗
PubMed1987

Occupational factors associated with astrocytomas: a case-control study.

The most malignant form of all brain tumors is the supratentorial astrocytoma. Little is known about its etiology, but exogenous factors have been blamed. In this case-control study, 78 astrocytoma patients have been compared with 197 clinical and 92 population controls. An extensive questionnaire was used to gather information about occupational and residential environment exposure. Inquiries concerning groups of or individual chemicals elicited low rates of affirmative response, with negligible differences between cases and controls. However, the questions "working at an airfield" and "living near a petrochemical plant" indicated elevated risks in comparison with both control groups; so too did "living near a municipal sewage treatment plant." These results focus attention on exposure to organic compounds and should be considered together with similar findings in current research. No other occupation, branch of industry, or vicinity questions showed differences between cases and controls, with the exception of "living in the neighborhood of a paper mill or a saw mill," which gave moderately increased relative risks. A separate report gives the results from the nonoccupational part of the study.

Cerebellar Neoplasms↗
PubMed1987

Hospital versus population referents in two case-referent studies.

In case-referent studies, the choice between hospital and population referents involves the consideration of nonresponse, information bias, and selection bias. A case-referent study of astrocytoma and one of pancreatic cancer used both hospital and population referents. In the present report the two series of referents were compared with regard to potential sources of systematic errors. There were differences in reported exposure between the hospital and population referents. These differences seemed to be due to differences in exposure experience ("selection bias") rather than to differences in the quality of reported information ("information bias"). This conclusion was based on two findings. First, in the comparison between the hospital and population referents, similar differences were found in the reported exposure for "hard" questionnaire items as for "soft" questionnaire items. Second, in a comparison between reported radiographs and radiographs according to medical records, the same differences were found for the two series of referents, although there was considerable underreporting of such exposure in both series. Nonresponse rates were somewhat higher among the population referents than among the hospital referents.

Epidemiologic Methods↗