The feasibility of conducting occupational epidemiology in the UK.
A postal survey was carried out of 1,000 UK companies to collect information about employee biographical and work history records. The overall response rate was 46%. All companies collected surname, forenames, address, date of birth and National Insurance number--information needed for cross-sectional studies. Other biographical details such as maiden name and National Health Service number were collected less often, which could increase the cost and difficulty of tracing ex-employees. Seventy per cent reported destroying their records within 10 years of an employee leaving, rising to 82% for companies with fewer than 100 employees. The destruction of employee records creates problems for historical cohort studies and case-control studies, and may hamper ex-employees trying to claim benefit for occupational-related illness. If the scope of future occupational epidemiology is to be improved, guidelines for the collection and retention of the data required must be developed and industry encouraged to participate. (+info)
Passive smoking and the risk of coronary heart disease--a meta-analysis of epidemiologic studies.
BACKGROUND: The effect of passive smoking on the risk of coronary heart disease is controversial. We conducted a meta-analysis of the risk of coronary heart disease associated with passive smoking among nonsmokers. METHODS: We searched the Medline and Dissertation Abstracts Online data bases and reviewed citations in relevant articles to identify 18 epidemiologic (10 cohort and 8 case-control) studies that met prestated inclusion criteria. Information on the designs of the studies, the characteristics of the study subjects, exposure and outcome measures, control for potential confounding factors, and risk estimates was abstracted independently by three investigators using a standardized protocol. RESULTS: Overall, nonsmokers exposed to environmental smoke had a relative risk of coronary heart disease of 1.25 (95 percent confidence interval, 1.17 to 1.32) as compared with nonsmokers not exposed to smoke. Passive smoking was consistently associated with an increased relative risk of coronary heart disease in cohort studies (relative risk, 1.21; 95 percent confidence interval, 1.14 to 1.30), in case-control studies (relative risk, 1.51; 95 percent confidence interval, 1.26 to 1.81), in men (relative risk, 1.22; 95 percent confidence interval, 1.10 to 1.35), in women (relative risk, 1.24; 95 percent confidence interval, 1.15 to 1.34), and in those exposed to smoking at home (relative risk, 1.17; 95 percent confidence interval, 1.11 to 1.24) or in the workplace (relative risk, 1.11; 95 percent confidence interval, 1.00 to 1.23). A significant dose-response relation was identified, with respective relative risks of 1.23 and 1.31 for nonsmokers who were exposed to the smoke of 1 to 19 cigarettes per day and those who were exposed to the smoke of 20 or more cigarettes per day, as compared with nonsmokers not exposed to smoke (P=0.006 for linear trend). CONCLUSIONS: Passive smoking is associated with a small increase in the risk of coronary heart disease. Given the high prevalence of cigarette smoking, the public health consequences of passive smoking with regard to coronary heart disease may be important. (+info)
Cigarette smoking and other risk factors in relation to p53 expression in breast cancer among young women.
p53 mutations may be a fingerprint for cigarette smoking and other environmental carcinogens, including breast carcinogens. This study was undertaken to explore whether p53 mutations are associated with environmental or other suspected or established risk factors for breast cancer. p53 protein detection by immunohistochemistry (which is more easily quantified in large epidemiological studies than are mutations, and are highly correlated with them) was determined for 378 patients from a case-control study of breast cancer. In this population-based sample of women under the age of 45 years, 44.4% (168/378) of the cases had p53 protein detected by immunohistochemistry (p53+). Polytomous logistic regression was used to calculate the odds ratios (ORs) for p53+ and p53- breast cancer, as compared with the controls, in relation to cigarette smoking and other factors. The ratio of the ORs was used as an indicator of heterogeneity in risk for p53+ versus p53- cancer. The ratio of the ORs in a multivariate model was substantially elevated among women with a greater than high school education [2.39; 95% confidence interval (CI), 1.43-4.00], current cigarette smokers (1.96; 95% CI, 1.10-3.52), and users of electric blankets, water beds, or mattresses (1.78; 95% CI, 1.11-2.86). Nonsignificant heterogeneity was noted for family history of breast cancer and ethnicity but not for other known or suspected risk factors. Coupled with the strong biological plausibility of the association, our data support the hypothesis that in breast cancer, as with other tumors, p53 protein immunohistochemical detection may be associated with exposure to environmental carcinogens such as cigarette smoking. (+info)
Components of variance and intraclass correlations for the design of community-based surveys and intervention studies: data from the Health Survey for England 1994.
The authors estimated components of variance and intraclass correlation coefficients (ICCs) to aid in the design of complex surveys and community intervention studies by analyzing data from the Health Survey for England 1994. This cross-sectional survey of English adults included data on a range of lifestyle risk factors and health outcomes. For the survey, households were sampled in 720 postal code sectors nested within 177 district health authorities and 14 regional health authorities. Study subjects were adults aged 16 years or more. ICCs and components of variance were estimated from a nested random-effects analysis of variance. Results are presented at the district health authority, postal code sector, and household levels. Between-cluster variation was evident at each level of clustering. In these data, ICCs were inversely related to cluster size, but design effects could be substantial when the cluster size was large. Most ICCs were below 0.01 at the district health authority level, and they were mostly below 0.05 at the postal code sector level. At the household level, many ICCs were in the range of 0.0-0.3. These data may provide useful information for the design of epidemiologic studies in which the units sampled or allocated range in size from households to large administrative areas. (+info)
Energy balance and cancers.
Energy balance results from the exact equilibrium between caloric intake and caloric expenditure. A caloric intake larger than caloric expenditure results in overweight, even obesity, but other determinants, like hormonal dysfunction and/or genetic traits may play a part in obesity syndrome. Obesity, and even overweight, have been recognized as risk factors for the development of cancers. Human epidemiological studies, which have tended to establish the nature of the relationship between energy balance and cancer, are summarized first, with the influence of the various factors which act both on obesity and on cancer risk. Among these factors are the macronutrients responsible for the caloric intake, and some lifestyle factors (physical activity, drinking habits and tobacco use). Second, the animal studies help to distinguish between different relevant factors, and to understand some of the underlying mechanisms. However, the insulin-resistance syndrome, which appears to underlie the relationship between obesity and hormone-dependent cancers, and possibly colon cancer, is only relevant to human physiology because hormonal alterations are part of it. Prevention of hyperinsulinemia, insulin resistance and the accompanying visceral obesity appears to be a major public health task for the prevention of cancers. (+info)
Confounding by indication: an example of variation in the use of epidemiologic terminology.
Confounding by indication is a term used when a variable is a risk factor for a disease among nonexposed persons and is associated with the exposure of interest in the population from which the cases derive, without being an intermediate step in the causal pathway between the exposure and the disease. However, in the literature, the term confounding by indication is not always used consistently. The authors found three different situations in which the term has been applied or might have been used but was not: confounding by indication as protopathic bias, as confounding by severity, or as a form of selection bias. It might be helpful to limit use of the term confounding by indication to the situation in which the disease that forms the indication acts as a confounder irrespective of its severity and to apply the term confounding by severity if the severity of this disease acts as a confounder. Protopathic bias and selection bias should not be confused with these terms. The use of appropriate terms ultimately will improve communication among researchers and contribute to the clarity of their papers. (+info)
Food and nutrient exposures: what to consider when evaluating epidemiologic evidence.
Nutritional epidemiology is the science concerned with conducting research into the relation between diet and disease risk. The public has a great deal of interest in this issue. Much of that interest, however, is fueled by the publication of sensationalized, startling, and often contradictory health messages. Unfortunately, there is a great deal of confusion in both the scientific press and the public or lay press about the nature of nutritional epidemiology, its strengths, and its limitations. The purpose of this article is to discuss these strengths and limitations. It is hoped that clarification of these issues can help lead to a resolution of the research community's and lay public's misunderstandings about nutritional epidemiology research. (+info)
The role of epidemiology in developing nutritional recommendations: past, present, and future.
Observations of the relations between food choices and health have been made since ancient times, but epidemiology, which can be regarded as the science of systematically studying these relations, has played a key role in official nutritional guidance only in recent years. In the past 20 y the principal goal of nutritional guidance has changed from the prevention of nutritional deficiencies to the prevention of chronic diseases. This evolving purpose of nutritional guidance has demanded that nutritional epidemiology play an increasingly important role. Although no other type of nutritional science can equal epidemiology in the relevance of either the dietary exposures or the health outcomes, substantial problems limit the ability of nutritional epidemiology to convincingly prove causal associations. The classic criteria for causation are often not met by nutritional epidemiologic studies, in large part because many dietary factors are weak and do not show linear dose-response relations with disease risk within the range of exposures common in the population. The most important problem in nutritional epidemiology in the past has been the inaccuracy of dietary assessment. In the future, an additional problem will be the proliferation of hypotheses that can be tested in multiple ways among the many subgroups of the population that can be defined by factors such as age, sex, and genotype. Future progress in our understanding of the relations between diet and health will necessitate improved methods in nutritional epidemiology and a better integration of epidemiologic methods with those used in the clinical nutritional sciences. (+info)