| 21. |
- Holmberg, Lars, et al.
(author)
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A search for recall bias in a case-control study of diet and breast cancer
- 1996
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In: International Journal of Epidemiology. - 0300-5771 .- 1464-3685. ; 25:2, s. 235-244
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Journal article (peer-reviewed)abstract
- BACKGROUND. In retrospective studies of dietary habits and breast cancer risk, recall bias is a concern since diet has been publicized as a cause of breast cancer. METHODS. In a case-control study of diet and breast cancer risk nested within a cohort of women screened with mammography, we contrasted answers to a retrospective dietary interview with answers to a dietary questionnaire which was filled out before any diagnostic procedures for breast cancer were undertaken. The source population was all women aged 40-74 in two counties in Sweden invited to mammographic screening and asked to fill out a questionnaire before the screening. Cases and controls were subsequently defined -- matched on age, county of residence, and time of mammography -- and approached for an interview. RESULTS. In all, 265 cases and 431 controls participated in the study. Means of frequencies differed between the agreement in the questionnaire's and the interview's classifications of study subjects into quartiles of monthly intake varied between 31 percent and 57 percent. Kappa statistics in all food groups were below 0.41. In a regression analysis, case subjects with low responses on the questionnaire about intake of meat, snacks, and coffee and tea gave higher responses on interview than did controls who had low questionnaire responses for these food groups. The reverse was also true: cases' responses that were high on the questionnaire were lower on interview for these food groups than were controls' responses. CONCLUSIONS. We found few signs of recall bias, and the few indications of a differential misclassification that we found were not in food groups that have been publicly discussed as causes of breast cancer.
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| 22. |
- Holmberg, Lars, et al.
(author)
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Alcohol intake and breast cancer risk : effect of exposure from 15 years of age
- 1995
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In: Cancer Epidemiology, Biomarkers and Prevention. - 1055-9965 .- 1538-7755. ; 4:8, s. 843-847
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Journal article (peer-reviewed)abstract
- Research regarding the relationship between alcohol intake and breast cancer risk has suggested an association between the two, although the data are inconsistent regarding dose effects and susceptible populations. To clarify these issues, we investigated the association of breast cancer risk with alcohol intake at various ages in a population-based case-control study nested within a screening cohort in Sweden. Subjects were women 40-75 years old who participated in a screening program in central Sweden. Information about personal characteristics, diet, and alcohol intake was obtained by a questionnaire sent out at the invitation to the screening interview and at a supplementary interview conducted among a sample of women who did and did not develop breast cancer. Alcohol intake did not affect breast cancer risk among women under 50 years old. However, among those over 50 years of age, ever-drinking conferred a relative risk of 1.8 (95% confidence interval = 1.2-2.6). Current and former drinkers had similar increases in risk. No particular latent period of alcohol effect was identified, but drinking later in life to have a bigger effect than did drinking earlier in life.
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| 23. |
- Holmberg, Lars, et al.
(author)
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On the scientific inference from clinical trials
- 1999
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In: Journal of Evaluation In Clinical Practice. - : Wiley. - 1356-1294 .- 1365-2753. ; 5:2, s. 157-162
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Journal article (peer-reviewed)abstract
- We have not been able to describe clearly how we generalize findings from a study to our own 'everyday patients'. This difficulty is not surprising, since generalization deals with how empirical observations are related to the growth of scientific knowledge, which is a major philosophical problem. An argument, sometimes used to discard evidence from a trial, is that the patient sample was too selected and therefore not 'representative' enough for the results to be meaningful for generalization. In this paper, we discuss issues of representativeness and generalizability. Other authors have shown that generalization cannot only depend on statistical inference. Then, how do randomized clinical trials contribute to the growth of knowledge? We discuss three aspects of the randomized clinical trial (Mant 1999), First, the trial is an empirical experiment set up to study the intervention on the question as specifically and as much in isolation from other -- biasing and confounding -- factors as possible (Rothman & Greenland 1998). Second, the trial is set up to challenge our prevailing hypotheses (or prejudices) and the trial is above all a help in error elimination (Popper 1992). Third, we need to learn to see new, unexpected and thought-provoking patterns in the data from a trial. Point one -- and partly point two -- refers to the paradigm of the controlled experiment in scientific method. How much a study contributes to our knowledge, with respect to points two and three, relates to its originality. In none of these respects is the representativeness of the patients, or the clinical situations, crucial for judging the study and its possible inferences. However, we also discuss that the biological domain of disease that was studied in a particular trial has to be taken into account. Thus, the inference drawn from a clinical study is not only a question of statistical generalization, but must include a jump from the world of experiences into the world of reason, assessment and theoretical judgement.
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| 24. |
- Johansson, Jan-Erik, et al.
(author)
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Fifteen-year survival in prostate cancer : a prospective, population-based study in Sweden
- 1997
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In: Journal of the American Medical Association (JAMA). - : American Medical Association (AMA). - 0098-7484 .- 1538-3598. ; 277:6, s. 467-471
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Journal article (peer-reviewed)abstract
- OBJECTIVE: To describe the natural history of initially untreated early-stage prostate cancer. A key secondary objective was to calculate long-term survival rates by stage, grade, and age at diagnosis. DESIGN: Prospective cohort study. SETTING: Population-based in 1 county of Sweden, without screening for prostate cancer. PATIENTS: A group of 642 patients with prostate cancer of any stage, consecutively diagnosed between 1977 and 1984 at a mean age of 72 years with complete follow-up to 1994. MAIN OUTCOME MEASURES: Proportion of patients who died from prostate cancer, and 15-year survival (with 95% confidence interval [CI]), corrected for causes of death other than prostate cancer. RESULTS: In the entire cohort, prostate cancer accounted for 201 (37%) of all 541 deaths. Among 300 patients with a diagnosis of localized disease (T0-T2), 33 (11%) died of prostate cancer. In this group, the corrected 15-year survival rate was similar in 223 patients with deferred treatment (81%; 95% CI, 72%-89%) and in 77 who received initial treatment (81%; 95% CI, 67%-95%). The corrected 15-year survival was 57% (95% CI, 45%-68%) in 183 patients with locally advanced cancer (T3-T4) and 6% (95% CI, 0%-12%) in those 159 who had distant metastases at the time of diagnosis. CONCLUSION: Patients with localized prostate cancer have a favorable outlook following watchful waiting, and the number of deaths potentially avoidable by radical initial treatment is limited. Without reliable prognostic indicators, an aggressive approach to all patients with early disease would entail substantial overtreatment. In contrast, patients with locally advanced or metastatic disease need trials of aggressive therapy to improve their poor prognosis.
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| 25. |
- Josefsson, Agnetha M., et al.
(author)
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p53 polymorphism and risk of cervical cancer
- 1998
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 396:6711, s. 531-
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Journal article (peer-reviewed)
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| 26. |
- Lambe, Mats, et al.
(author)
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Malignant melanoma : reduced risk associated with early childbearing and multiparity
- 1996
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In: Melanoma research. - : Ovid Technologies (Wolters Kluwer Health). - 0960-8931 .- 1473-5636. ; 6:2, s. 147-153
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Journal article (peer-reviewed)abstract
- Pigmentary changes during pregnancy and sex-specific differences in incidence patterns of cutaneous malignant melanoma (CMM) suggest that sex hormones may be involved in the development of CMM. We explored possible associations between childbearing and the risk of CMM in a case-control study "nested' in a nation-wide cohort. A total of 4,779 incident cases of CMM in women aged 24-65 were compared with 23,888 individually age-matched controls. Delayed childbearing was associated with an increased risk of CMM, corresponding to approximately 16% per 5 years. Parous women had a significantly lower risk of CMM compared with nulliparous women; in univariate analysis there was an 8% reduction in risk for each additional birth (odds ratio = 0.92; 95% confidence interval = 0.89-0.95). In multivariate analyses the risk of CMM was best explained by a model including both age at first birth and parity. Age at first birth was the most important variable. Time since most recent birth was unrelated to risk of CMM. These findings indicate that early childbearing and multiparity reduce the risk of CMM. Conceivable explanations are hormonal changes induced by childbearing, enhanced immunologic activity via exposure to fetal antigens during pregnancy, or long-lasting effects of pregnancy-associated hyperpigmentation. Our results need confirmation in studies with proper adjustment for confounding; less sun exposure in young mothers and high parity women may represent an alternative explanation but is unlikely to explain entirely the twofold difference in risk found between extreme categories of age at first birth and parity.
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| 27. |
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| 28. |
- Linet, Martha S., et al.
(author)
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Maternal and perinatal risk factors for childhood brain tumors (Sweden)
- 1996
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In: Cancer Causes and Control. - 0957-5243 .- 1573-7225. ; 7:4, s. 437-448
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Journal article (peer-reviewed)abstract
- Childhood brain tumors (CBT) include a diversity of rare neoplasms of largely unknown etiology. To assess possible maternal and perinatal risk factors for CBT according to subtype, we carried out a nested (within Swedish birth-cohorts, 1973-89) case-control study, utilizing data from the nationwide Birth Registry. We ascertained incident brain tumor cases through linkage of the nationwide Birth and Cancer Registries and randomly selected five living controls from the former, matching each case on gender and birthdate. There were 570 CBT cases, including 205 low grade astrocytomas, 58 high grade astrocytomas, 93 medulloblastomas, 54 ependymomas, and 160 'others.' Risks for all brain tumors combined were elevated in relation to: (i) three maternal exposures-oral contraceptives prior to conception (odds ratios [OR] = 1.6, 95 percent confidence interval [CI] = 1.0-2.8), use of narcotics (OR = 1.3, CI = 1.0-1.6), or penthrane (OR = 1.5, CI = 1.1-2.0) during delivery); (ii) characteristics of neonatal distress (a combined variable including low one-minute Apgar score, asphyxia [OR = 1.5, CI = 1.1-2.0]) or treatments for neonatal distress (use of supplemental oxygen, ventilated on mask, use of incubator, scalp vein infusion, feeding with a jejunal tube [OR = 1.6, CI = 0.9-2.6]); and (iii) neonatal infections (OR = 2.4, CI = 1.5-4.0). Higher subtype-specific risks, observed for a few risk factors, did not differ significantly from the risk estimates for all subtypes combined for the corresponding risk factors. Childhood brain tumors were not associated significantly with other maternal reproductive, lifestyle, or disease factors; perinatal pain, anesthetic medications, birth-related complications; or with birthweight, birth defects, or early neonatal diseases. These findings suggest several new leads, but only weak evidence of brain tumor subtype-specific differences.
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| 29. |
- Lipworth, L., et al.
(author)
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Maternal pregnancy hormone levels in an area with a high incidence (Boston, USA) and in an area with a low incidence (Shanghai, China) of breast cancer
- 1999
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In: British Journal of Cancer. - : Springer Science and Business Media LLC. - 0007-0920 .- 1532-1827. ; 79:1, s. 7-12
-
Journal article (peer-reviewed)abstract
- Characteristics probably associated with the fetal hormonal milieu have recently been shown to increase (birth size indicators, prematurity, neonatal jaundice) or decrease (pregnancy toxaemia) breast cancer risk in the female offspring. However, it is unknown whether differences in pregnancy hormone levels may contribute to the marked geographical variation in breast cancer incidence. We have compared, in a highly standardized manner, pregnancy hormone levels in a population with high incidence and one with low incidence of breast cancer. Three hundred and four pregnant Caucasian women in Boston and 334 pregnant Chinese women in Shanghai were enrolled from March 1994 to October 1995. Levels of oestradiol, oestriol, prolactin, progesterone, human growth hormone, albumin and sex hormone-binding globulin were measured in maternal blood at weeks 16 and 27 of gestation and compared between the two study sites using non-parametric Wilcoxon's rank-sum test. Demographical, anthropometrical and pregnancy characteristics were ascertained through interview, and relevant variables concerning delivery and the newborn were abstracted from medical records and paediatric charts. During the first visit, median serum levels of all studied hormones were statistically significant, and in most instances substantially, higher among Chinese women, who have a low incidence of breast cancer, compared with American women, who have a high incidence of breast cancer. An analogous pattern was evident during the second visit, although the relative differences tended to be smaller. Further research is needed to identify lifestyle or other exogenous determinants of pregnancy hormone levels, as well as possible mechanisms by which they may influence carcinogenic processes in the breast and possibly other organs.
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| 30. |
- Ljungman, Christer, et al.
(author)
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Amputation risk and survival after embolectomy for acute arterial ischaemia : Time trends in a defined Swedish population
- 1996
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In: European Journal of Vascular and Endovascular Surgery. - 1078-5884 .- 1532-2165. ; 11:2, s. 176-182
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Journal article (peer-reviewed)abstract
- OBJECTIVES: To assess the outcome of embolectomy over an 19 year period. METHODS: Time trends in the outcome of acute arterial thrombo-embolectomy of the extremities were analysed in a population-based cohort of 1190 patients operated on between 1965-83. RESULTS: A total of 262 (22%) initial amputations were performed. The limb salvage rates at 5 years postoperatively were lower between 1975-79 (61%) than between 1965-69 (81%). A proportional hazards model revealed a relative hazard (RH) of amputation of 2.2 (95% confidence interval (CI) 1.3-3.3) for 1975-79 compared with 1965-69. Operation at any district hospital entailed a 70% higher risk of amputation (RH 1.7; 95% CI 1.3-2.5) compared with the University hospital. The relative survival rate at 5 years postoperatively decreased towards the end of the study period (33% between 1975-79 compared with 43% between 1965-69). Younger age-groups had a considerably lower risk of death in the University hospital compared with the county and district hospitals. CONCLUSIONS: Contrary to the results in other hospital based reports no improvement in amputation or survival rates since 1965 could be demonstrated in this large series with no patient selection.
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