Journal of epidemiology and biostatistics最新文献

Background: Family history of stroke has been considered as a risk factor for stroke, but this relationship is controversial. Some, but not all, studies have found an independent association between family history of stroke and stroke. This study examines the relationship between family history of stroke and all stroke types combined, cerebral infarction and intraparenchymatous haemorrhage.

Methods: This is an incidence type, population-based case-control study. Cases were defined following WHO criteria and controls were randomly selected from the study-base population. Family history of stroke was obtained by medical interview. A total of 470 cases and 477 controls, aged 40-85 years, form the subjects of the study.

Results: Family history of stroke in a first-degree relative is an independent risk factor for all stroke types combined, multivariate adjusted odds ratio (OR) 1.74, 95% confidence interval (CI) 1.24-2.44, for cerebral infarction, OR = 1.79 (95% CI 1.25-2.56), but not for intraparenchymatous haemorrhage, OR = 1.71 (95% CI 0.91-3.17). Risk of all stroke types combined was independently associated with a positive history of father with stroke OR = 1.93 (1.19-3.54) with a positive history of sibling with stroke, OR = 1.67 (95% CI 1.03-2.71) and a borderline significant association with a positive history of mother with stroke OR = 1.45 (95% CI 0.92-2.29). Cerebral infarction was independently associated with a positive history of father with stroke OR = 2.05 (95% CI 1.17-3.59), a positive history of sibling, OR = 1.69 (95% CI 1.01-2.84) and a borderline significant association with a positive history of mother with stroke OR = 1.58 (95% CI 0.97-2.56). Intracerebral haemorrhage was not significantly associated with a positive history of father with stroke OR = 1.39 (0.55-3.58) with a positive history of sibling, OR = 1.83 (95% CI 0.77-4.40), or with a positive history of mother with stroke OR = 1.36 (95% CI 0.59-3.09).

Conclusions: Family history of stroke is found in this study to be an independent risk factor for all stroke types combined and for cerebral infarction. Genetic factors may be involved, but it cannot be ruled out that the observed relationship is confounded by other risk factors, especially family aggregation of life-styles.

Background: Incidence and mortality rates of kidney cancer are known to be increasing world-wide. The reasons for these increases are not clear, but despite this it may still be possible to predict changes in the trend of occurrence.

Methods: Male and female kidney (plus ureter and urethra) cancer mortality per 10(5) person-years, from 1950 to 94, were calculated using national demographic and mortality data. Changes in the age structure of the Dutch population were adjusted using direct standardisation to the European standard population. The effects of age, calendar period and birth cohort on the temporal trend in mortality were evaluated using log-linear modelling.

Results: Male mortality from kidney cancer increased from three per 10(5) person-years in the 1950s to eight per 10(5) in the mid 1980s and remained relatively stable thereafter. Female mortality rates showed a comparable trend, from two per 10(5) in the 1950s to four per 10(5) in the 1980s. In addition to the effects of age, the temporal trend in males can be sufficiently explained as a birth cohort effect. Successive birth cohorts appear to have higher risks of dying from kidney cancer until the 1930 cohort. The younger birth cohorts appear to have lower risks. The trend in women is comparable to that in men but is less pronounced and shows only after excluding women under the age of 45.

Conclusion: The decreasing risk for generations born after 1930 will probably result in a decreasing trend in kidney cancer mortality in the near future. It is suggested that at least part of this changing trend in men (but not in women) is caused by the changing smoking behaviour of the Dutch population.

Background: Live-birth (male-female) ratios are a standard measure used in demography. Recently, live-birth ratios have been considered as a potential indicator for various environmental hazards. In this paper, mixture modeling is applied to analyse the geographic heterogeneity of live-births in their composition of male and female proportions (live-birth ratio) in the Kingdom of Thailand.

Methods: Live-birth data are taken from the 1990 census of the Kingdom of Thailand. The level of aggregation is the province, of which there are 73 in Thailand. The analysis is based on the simple observation that a logical equivalent to the live-birth ratio is available, namely the proportion of male live-births. Based on this measure a simple and exact statistical model is easily derived: conditional on the number of live-births, the number of male live-births forms a binomial distribution, with parameter lambda. If there is homogeneity in the proportion of male live-births, then all provinces can be described by means of a single binomial distribution. However, if there is heterogeneity in the proportion parameter lambda, then a mixture of binomial distributions will occur.

Results: For the 1990 census data, three groups could be identified: a majority group containing 84% of the provinces and a proportion parameter of lambda = 0.513, a group of five provinces having a reduced proportion parameter of lambda = 0.500 (fewer male live-births), and a group of four provinces having an increased proportion parameter of lambda = 0.525.

Conclusions: It is unclear how this can be explained, although some potential explanations are offered. The stability of these groups in time should be confirmed and regularly monitored.

The benefits of oestrogen replacement therapy (ERT) in preventing vasomotor symptoms, cardiovascular disease, osteoporosis, and colon cancer are well documented. Other potential benefits i.e. dementia and macular degeneration are being investigated. Although oestrogen is said to be contraindicated in women previously treated for breast and endometrial cancer, there is no data to support this admonition. Preliminary data would suggest ERT can be used safely in women who have had these cancers. Prospective randomised studies are currently on going in the United States and Europe addressing ERT in previously treated breast and endometrial cancer. Informed consent, patients' desires, and benefit-risk considerations are all part of information the woman needs to make a decision concerning ERT.

Background: Our objective was to develop and test a methodology for inferring the percentage of prisoners currently using opiates from the percentage of prisoners testing positive for opiates in random mandatory drugs testing (rMDT).

Methods: The study used results from Willing Anonymous Salivary HIV (WASH) studies (1994-6) in six adult Scottish prisons, and surveys (1994-5 and 1997) in 14 prisons in England and Wales. For Scottish prisons, the percentage of prisoners currently using opiates was determined by assuming, with varying empirical support, that: current users of opiates in prison were 1.5 times as many as current inside-injectors; and current inside-injectors were 0.75 times as many as ever injectors in prison. We also assumed that current inside-users' frequency of use of opiates (by any route) was equal to the frequency of inside-injecting by current inside-injectors in Aberdeen and Lowmoss Prisons in 1996, namely six times in 4 weeks. We assumed that some scheduling of heroin-use prior to weekends takes place, so that only 50% of current inside-users of opiates would test positive for opiates in rMDT: these assumptions allow us to arrive at WASH-based expectations for the total percentage of prisoners testing positive for opiates in rMDT. For England and Wales, a multiplier of 118/68 was applied which was derived from prisoners' interviews, to convert the results from ever inside-injectors, as determined by WASH studies, to the percentage of current inside users of opiates. We made the same assumptions on frequency of inside-use of opiates as in dealing with the Scottish results.

Results: We expected 202.7 opiate positive results in April to September 1997 in rMDTs at six adult prisons in Scotland, 226 were observed. We expected 227.0 at a set of 13 adult prisons and one other in England and Wales; 211 were observed.

Conclusions: Further testing of the methodology for prisons in England and Wales will be possible when 1997 WASH data are released. So far, the methodology has performed well. From it, we infer that 24% of inmates at the six adult prisons in Scotland were current inside-users of opiates, compared to 11% at the 14 adult prisons where survey data were available in England and Wales. The corresponding April to September 1997 percentage of opiate positives in rMDT were: 13% (results from the six Scottish prisons) and 5.4% (results from 14 prisons in England and Wales), a two-fold under-estimate of % current users of opiates in prison (24% and 11%). Planning of drug rehabilitation places for prisoners should thus be based on twice the percentage of prisoners testing opiate positive in rMDT. This correction factor of two should be kept under review.

From investigations of smoking habits, which included information about onset of smoking, we have extrapolated gender- and age-specific smoking prevalence in Germany back to the 1920s. The exploration of these data, together with an analysis of lung cancer mortality by age-period-cohort models shows that the increase of smoking and lung cancer is modulated by factors related to the country-specific socio-economic environment and that it proceeds in waves. Though recent data indicate a decline in the prevalence of smoking among both sexes, Germany is now on the way to having a similar smoking-related cancer mortality to those countries in the world which previously had a much higher rate, but have intervened vigorously. The refusal in Germany to adopt actions such as those successfully implemented to save lives in these countries means that the German population is exposed to avoidable risks, whose effects can be counted in the terms of the thousands of lives that might have been saved each year.

Formulation of HRT preparations has changed very significantly over the last few decades. The problems of unopposed oestrogens are now well recognised. Addition of progestins may overcome these problems in some target tissues. However, there is clear evidence for differential effects of both steroids in different target tissues. It is also vital to be clear on the dose-response to each steroid in each target tissue. Steroids given orally may undergo different metabolism from those given transdermally or subcutaneously. This can mean that, even given dose for dose, there can still be differences in the regulation of, for example, lipid profiles, depending on delivery route. The situation is further complicated by the discovery that there is more than one receptor for each steroid. Steroid receptors are members of the super-family of nuclear receptors. Steroid enters the cell, binds and activates empty receptors, inducing dimerisation and acquisition of high affinity for specific sequences of nucleotides within the hormone-response elements (HRE) of the target genes. Hormone-receptor complex interacts with the HRE to modulate transcription of the gene. The different receptors for each steroid (e.g. oestrogen receptors alpha and beta) help promote the differential responses in different target tissues. Analysis of the overall responses to HRT requires a knowledge of the dose and specificity of each steroid within the formulation, together with an understanding of how each steroid regulates the activities of each sub-group of receptors in each target tissue, allowing for the appropriate metabolism of the primary steroids. Additionally, there will be variations among different individuals.

Background: Smoking is a well-known risk factor for coronary heart disease (CHD). The components of tobacco that cause CHD have not yet been established; nor have the relative dangers of cigarettes of different strengths.

Methods: This is a cohort study of 2,849 men and 2,900 women with no symptoms of CHD at baseline in the Scottish Heart Health Study.

Results: In a 7.7 year follow-up, to 1993, there were 123 male and 49 female CHD events. After adjusting for age, cholesterol and blood pressure, men who smoke > or = 20 cigarettes per day have a relative hazard [95% confidence interval (CI)] of 1.93 (1.15-3.24) compared with non-smokers; for women the corresponding relative hazard is 3.81 (2.00-7.27). Biochemical measures (cotinine, thiocyanate and expired-air CO) are closely correlated with self-reported smoking (0.67 < or = r < or = 0.72), and have similar relationships with CHD. Amongst cigarette smokers, relative hazards (third to first tertile), for tar yield are 1.05 (0.54-2.07) for men and 4.00 (1.13-14.18) for women. Nicotine and CO yields give similar results. Hazard ratios associated with heavy smoking and strong cigarettes are thus much higher for women.

Conclusion: Although smoking was found to have a detrimental effect, this study was unable to suggest a single major cause of CHD. The excess effects found in women compared with men could be due to differences in former smoking habits. Furthermore, risk differences for smoking are slightly greater for men, explained by the relatively low incidence of CHD amongst women.

Background: This cohort study examines the association between cigarette smoking and risk of fibroadenoma.

Methods: The study was conducted among the 56,537 women in the Canadian National Breast Screening Study (NBSS) who completed self-administered lifestyle and dietary questionnaires. (The NBSS is a randomised, controlled trial of screening for breast cancer in women aged 40-59 at recruitment.) Cases were the 222 women who were diagnosed with biopsy-confirmed incident fibroadenoma. For comparative purposes, a subcohort, consisting of a random sample of 5,681 women was selected from the full dietary cohort. After exclusions for various reasons, the analyses were based on 222 cases and 5,488 non-cases. Incidence rate ratios (IRR) and 95% confidence intervals (CI) were estimated using Poisson regression.

Results: Cigarette smoking was associated with reduced risk of fibroadenoma, the IRR (95% CI) for more than 550 cigarette-years of exposure being 0.66 (0.40-1.10). Although the reduction in risk was evident for all smokers combined (ex-smokers and current smokers), it was indicative largely of an inverse association in current smokers, in whom the IRR (95% CI) for > 300 cigarette-years of exposure was 0.49 (0.24-0.98). The results were mostly the same when examined in strata defined by method of detection of fibroadenoma, menopausal status and history of previous breast disease. There was no evidence for a reduction in risk with time since last use of cigarettes.

Conclusions: The results of this study suggest that cigarette smoking is associated with reduced risk of fibroadenoma, especially in current smokers.

Background: This paper presents an evaluation of two methods of measurement error adjustment based on recently-developed computer routines (RCAL and SIMEX) under logistic regression models, when one of the two predictors is subject to additive measurement error or Berkson error.

Methods: Computer simulations were used to generate data under a variety of conditions and the methods compared in terms of bias, mean squared error and confidence interval coverage of the regression estimates.

Results: Based on our investigations, RCAL was shown to perform very well in all situations considered, except in the presence of Berkson error when the predictor variables were highly correlated.

Conclusions: Since measurement error can lead to misleading inference, it is important to adjust for measurement error in the application of logistic regression. Until better measurement error adjustment methods become available, we recommend RCAL on the basis of our simulation results.