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A Ahlbom

Publications and source records attributed to A Ahlbom.

At least 91 records · Page 5Linked to original sources
PubMed1993

Predicting dementia from the Mini-Mental State Examination in an elderly population: the role of education.

Our study aimed to assess whether education affects the positive predictive value of the MMSE when it is used as a screening test for dementia. The MMSE has been consistently found to correlate with education and, at the same time, education is regarded by some researchers as being of potential etiological significance for dementia. In the present study, results on the MMSE from a community-based study in Sweden were compared with two standards: the clinical diagnosis of dementia and the Katz index of daily living activities. For both these comparisons, education did not substantially change the predictive ability of the MMSE. Our data, when compared with previous studies, show that the influence of education on the predictive ability of the MMSE varies in different populations. We conclude that differential MMSE cut-off points for different educational levels or adjustment techniques for education are not universally applicable.

Aged↗
PubMed1993

Risk indicators for inflammatory bowel disease.

We investigated the association between different risk indicators and inflammatory bowel disease in a case-control study based on the population of Stockholm County during 1980-1984. Information on physical activity, oral contraceptives, some previous diseases and childhood characteristics was collected using a postal questionnaire for 152 cases of Crohn's disease, 145 cases of ulcerative colitis, and 305 controls. The relative risk (RR) of Crohn's disease was inversely related to regular physical activity and estimated at 0.6 (95% CI: 0.4-0.9) and 0.5 (95% CI: 0.3-0.9) for weekly and daily exercise, respectively. Having psoriasis prior to the inflammatory bowel disease was associated with an increased relative risk of Crohn's disease (RR = 2.9, 95% CI: 1.1-7.9). Use of oral contraceptives was associated with an increased RR of 1.7 for both Crohn's disease and ulcerative colitis. Crohn's disease confined to the colon and total ulcerative colitis at diagnosis were most strongly associated with oral contraceptives.

Adolescent↗
PubMed1993

Use of oral moist snuff and inflammatory bowel disease.

We examined the association between oral moist snuff use and inflammatory bowel disease in a case-control study based on the population in Stockholm County. The relative risk (RR) associated with ever use of moist snuff was 2.1 (95% CI: 1.0-4.6) for Crohn's disease, and 2.2 (95% CI: 1.1-4.4) for ulcerative colitis. Cigarette smoking indicated a synergistic relation with moist snuff: the RR estimate of Crohn's disease was 3.7 (95% CI: 1.1-13.1) and of ulcerative colitis 3.3 (95% CI: 1.0-10.9) for snuff dippers who were also current cigarette smokers, but only 0.9 and 1.1 respectively for snuff dippers who had never smoked.

Adolescent↗
PubMed1992

Aspects of misclassification of confounding factors.

Misclassification of exposure in epidemiologic investigations has been extensively studied and is now well understood. In contrast, misclassification of confounding factors has been much less investigated. First, we consider a situation with confounding by age, in which misclassification is introduced through stratification of this inherently continuous variable. This misclassification turns out to be benign: 75% of the original confounding is removed by stratification into two age classes and more than 90% by using three age classes. Second, we consider a situation with serious confounding and serious misclassification of the confounding factor but no misclassification of the exposure. In this situation, the misclassification turns out to be of importance. After stratification for the misclassified confounding factor, it appears as though the exposure has a stronger effect on the incidence than the confounder, which is the reverse of the true situation.

Adult↗
PubMed1992

Childhood cancer among Swedish twins.

The risk of childhood cancer was evaluated among 35,582 twins born in Sweden between 1952 and 1967. Cancers were identified through linkage with national cancer and mortality registries. Overall, 59 childhood cancers and 41 deaths from cancer occurred before the age of 16. For both sexes combined, the cancer incidence was similar to that in the general population of primarily single-born children (number observed/number expected [O/E] = 1.0, 95 percent confidence interval [CI] = 0.7-1.2). For males under age five, cancer incidence was reduced significantly (O/E = 0.3, CI = 0.1-0.7). There was a substantial increase in all-cause mortality among twins (O/E = 3.7), attributable to a high mortality during the first year of life. Excluding this first year, the O/E for death (all causes) was 1.1 (CI = 1.0-1.3). For cancer mortality of both sexes, the O/E was 0.9 (CI = 0.6-1.2), with no significant reduction of risk in any sex-age group. We conclude that with the possible exception of males aged 0-4 years, the childhood cancer risk of twins appears similar to that of singletons.

Adolescent↗
PubMed1992

Diet and inflammatory bowel disease: a case-control study.

We conducted a population-based case-control study of inflammatory bowel disease and dietary habits in Stockholm during 1984-1987. We obtained retrospective information about food intake 5 years previously by a postal questionnaire for 152 cases with Crohn's disease, 145 cases with ulcerative colitis, and 305 controls. The relative risk of Crohn's disease was increased for subjects who had a high (55 gm or more per day) intake of sucrose (relative risk = 2.6, 95% confidence interval = 1.4-5.0) and was decreased for subjects who had a high (15 gm or more per day) intake of fiber (relative risk = 0.5, 95% confidence interval = 0.3-0.9). The most striking finding was an increased relative risk of both Crohn's disease and ulcerative colitis associated with consumption of fast foods: the relative risk associated with consumption of fast foods at least two times a week was estimated at 3.4 (95% confidence interval = 1.3-9.3) for Crohn's disease and 3.9 (95% confidence interval = 1.4-10.6) for ulcerative colitis. Although coffee seemed to provide a protective effect for both diseases, there are reasons to consider this finding an artifact.

Adolescent↗
PubMed1992

Geographical differences in myocardial infarction incidence in eight Swedish counties, 1976-1981.

Considerable regional variation in coronary heart disease mortality has been observed in Sweden. This variation is of public health concern and is also a point of departure for etiologic studies. The central aim of the present study was to investigate whether there are also regional differences in myocardial infarction incidence and to evaluate whether these are likely to be explained by regional differences in smoking, blood pressure, and serum cholesterol. The study base consisted of subjects age 30-64 living in eight Swedish counties during 1976-1981. Cases of myocardial infarction were identified using both hospital discharge and death records. A 30-40% increased incidence of myocardial infarction was found in the two northernmost counties compared with Stockholm county. The regional differences in myocardial infarction incidence were not related to differences in smoking but might be due in part to differences in serum cholesterol and blood pressure, and to socioeconomic factors as well.

Adult↗
PubMed1992

A definition of bias founded on the concept of the study base.

We propose a definition of bias founded on the concept of the study base. The definition is unrelated to the study design, thereby permitting a clear comparison of validity among different study types. Also, it facilitates assessment of bias because it allows bias to be subdivided under mutually exclusive categories. In relation to the study base, the epidemiologic study can be viewed as involving three distinct steps. First, the person-time (study base) is specified for the study. Second, the investigators collect data on disease events and person-time among the exposed and unexposed from the study base. Third, they calculate an estimate of the effect of the exposure using the data. Categories pertaining to each of these three steps will create mutually exclusive categories of bias. We suggest the following terminology: the first step generates confounding, the second results in misclassification and misrepresentation, and the third produces analysis deviation. The total bias is the sum of the confounding, misclassification, misrepresentation, and analysis deviation. We illustrate our proposed epidemiologic theory with examples from various biological settings.

Bias↗
PubMed1992

Differences in the incidence of myocardial infarction among occupational groups.

An inverse relationship between social class and coronary heart disease has been observed in several countries, but few studies have investigated the incidence of this disease over different occupational groups. A case-referent study was carried out to estimate the relative risk of a first myocardial infarction in various occupational groups. Cases of myocardial infarction (N = 36,602) were identified from both hospital discharge and death records. Two referents for each case were randomly selected from the study base. Information about occupation was obtained from two consecutive censuses. An increased incidence, compared with that of others employed, was found for persons in some occupations in production work, transport work (men), and service work (women). Low relative risk were found mainly for persons in occupations demanding a high education. The relative risks ranged from 0.3 to 2.8. Several factors, occupational as well as nonoccupational, may be of importance in explaining the findings.

Adult↗
PubMed1991

Is brain cancer mortality increasing in industrial countries?

This paper analyzes age-specific trends in brain and other central nervous system cancer mortality from 1968 to 1987 in several major industrial countries. It also examines changes in the use of diagnostic confirmation technology and trends in incidence in the U.S. National Cancer Institute, Surveillance, Epidemiology, and End Results (SEER) program from 1973 to 1987 to estimate the influence of diagnostic factors on recent mortality trends. Other sources of error have not been evaluated in this paper. Age-specific analyses of brain and other nervous system cancer mortality show drastic increases in persons ages 75-84 and consistent increases in younger age groups in most countries, although mortality declined in the U.S. in persons 0-24 by 2% annually. In the SEER program, brain cancer incidence increased significantly by 2%, 1%, and 5% annually in persons aged 0-44, 65-74, and 75-84, respectively. Throughout this time period, microscopic or radiographic confirmation occurred in at least 96% of all incident cases of brain and other central nervous system cancers diagnosed before death, with older persons receiving consistently more radiographic tests than younger persons. Changes in diagnoses across populations and over time are unlikely to account completely for these increasing trends which are occurring simultaneously in both males and females in major industrial countries. Additional studies need to be conducted, to exclude artifacts, to assist health care planners in anticipating treatment demands, and to detect preventable causes of these changing trends.

Adult↗
PubMed1991

Incidence of leukaemia and brain tumours in some "electrical occupations".

A 19 year follow up study was conducted to explore the association between occupations expected to be exposed to electromagnetic fields and the occurrence of leukaemia and brain tumours. Incidence of cancer between 1961-79 was calculated and the standardised morbidity ratio (SMR) with a 95% confidence interval (95% CI) was related to that of all Swedish working men. For all the selected "electrical occupations" the SMRs for total leukaemia and brain tumours were near unity. Increased risks were noted for all leukaemia among electrical/electronic engineers and technicians, (SMR 1.3; 95% CI 1.0-1.7) as well as in the sub-groups of telegraph/telephone (2.1; 1.1-3.6) and machine (2.6; 1.0-5.8) industries. Risk for chronic lymphoid leukaemia was increased in the same occupational category (1.7; 1.1-2.5) and in the sub-group of machine industry (4.8; 1.0-14.0), as well as for all linesmen (2.0; 1.0-3.5) and power linesmen (2.8; 1.1-5.7). Risk for acute myeloid leukaemia was increased among all miners (2.2; 1.0-4.1) and miners working in iron/ore mines (5.7; 2.1-12.4). Increased risk for all brain tumours (2.9; 1.2-5.9) and glioblastomas (3.4; 1.1-8.0) appeared among assemblers and repairmen in radio and TV industry. Raised risk for all brain tumours was seen for all welders (1.3; 1.0-1.7) and welders in iron/steel works (3.2; 1.0-7.4) and risk for glioblastomas was also increased for all welders (1.5; 1.1-2.1). No major changes in relative risk estimates were noted after the exclusion of persons who were over 65 at the time of diagnosis. Although a homogeneous pattern of increased risks of leukaemia or brain tumour was not noted, the hypothesis that magnetic fields might play a part in the origin of cancer cannot be rejected.

Adult↗