Douglas L. Weed

META-ANALYSIS OF PROSPECTIVE STUDIES OF RED MEAT CONSUMPTION AND COLORECTAL CANCER

The relationship between red meat consumption and colorectal cancer (CRC) has been the subject of scientific debate. To estimate the summary association between red meat intake and CRC and to examine sources of heterogeneity, a meta-analysis of prospective studies was conducted. Thirty-four prospective studies of red meat and CRC were identified, of which 25 represented independent nonoverlapping study populations. Summary relative risk estimates (SRREs) for high versus low intake and dose–response relationships were calculated. In the high versus low intake meta-analysis, the SRRE was 1.12 (95% CI: 1.04–1.21) with significant heterogeneity (P=0.014). Summary associations were modified by tumor site and sex. The SRREs for colon cancer and rectal cancer were 1.11 (95% CI: 1.03–1.19) and 1.19 (95% CI: 0.97–1.46), respectively. The SRREs among men and women were 1.21 (95% CI: 1.04–1.42) and 1.01 (95% CI: 0.87–1.17), respectively. The available epidemiologic data are not sufficient to support an independent and unequivocal positive association between red meat intake and CRC. This conclusion is based on summary associations that are weak in magnitude, heterogeneity across studies, inconsistent patterns of associations across the subgroup analyses, and the likely influence of confounding by other dietary and lifestyle factors.

Application of Population Screening Principles to Genetic Screening for Adult-Onset Conditions

Recent advances in molecular genetics have highlighted the potential use of genetic testing to screen for adult-onset chronic diseases. Several issues must be addressed, however, before such tests can be recommended for population-based prevention programs. These issues include the adequacy of the scientific evidence, the balance of risks and benefits, the need for counseling and informed consent, and the costs and resources required. Ongoing assessment of the screening program and quality assurance of laboratory testing are also needed. This paper considers the application of general principles for mass screening to genetic testing for susceptibility to adult-onset chronic diseases. Evaluation of proposals for genetic screening in context of these principles reveals that needed evidence is often absent, particularly with respect to the predictive value of tests, efficacy of interventions, and social consequences of testing. The principles of population screening are developed into a framework for public health policy on genetic screening that has three stages: assessment of the screening test and interventions for those who test positive, including assessment of risks and costs, policy development, and program evaluation. Essential elements are identified, including evaluation of evidence and processes for consensus development and program evaluation. The proposed framework for public health policymaking outlined in this commentary, when combined with future efforts that involve an authoritative consensus process, may be useful for the evaluation and planning of genetic screening programs aimed at reducing morbidity and mortality from adult-onset chronic diseases.

Measuring the Public Health Burden of Cancer in the United States Through Lifetime and Age-Conditional Risk Estimates

PURPOSEnEffects of an aging population in the United States on lifetime and age-conditional risk estimates of developing site-specific cancers are identified and the potential role these statistics play in monitoring disease burden discussed.nnnMETHODSnRisk estimates were derived by applying cross-sectional population-based incidence rates of cancer and mortality rates from other causes to a hypothetical cohort. The cohort was aged through a double decrement life table to determine the expected proportion of the population that would develop the disease.nnnRESULTSnDespite black men having higher invasive cancer incidence rates than white men, and black and white women having similar rates, because of the better life expectancy among whites lifetime risk estimates of developing cancer are higher for whites than blacks: 45.5% in white men, 40.4% in black men, 39.2% in white women, and 32.4% in black women based on 1995-97 data. White men experience higher 10-year cancer risk than black men in only bladder cancer, non-Hodgkins lymphomas (NHL), and leukemia. White women tended to show a greater risk than black women for cancers of the breast, corpus uteri, ovary, NHL, and leukemia. For both whites and blacks, the 10-year risk of lung cancer ranks first among men aged 40, ranks second to prostate cancer for men aged 50, 60, and 70, and ranks second to breast cancer for women aged 40, 50, 60, and 70.nnnCONCLUSIONSnLifetime and age-conditional risk measures reflect both changes in the disease incidence rates and age distribution over calendar time such that they are useful for monitoring the disease burden in the population. Even if cancer rates remain stable or fall, it is possible for the cancer burden, as reflected by lifetime and age-conditional risk estimates, to increase due to the aging population.

Science, Ethics Guidelines, and Advocacy in Epidemiology

This article examines current ethics guidelines for recommendations on advocacy as an acceptable activity for epidemiologists. Three sets of guidelines, those produced by the Industrial Epidemiology Forum (IEF), the International Epidemiological Association (IEA), and the Council of International Organizations of Medical Sciences (CIOMS), appear to endorse the role of advocate, although there are differences in their recommendations. The IEF guidelines hint that advocacy is appropriate, the IEA guidelines recommend separating the roles of scientist and advocate, and the CIOMS guidelines recommend advocacy dependent on the quality of epidemiologic research and on causal interpretations of the data. Advocacy in the form of public health recommendations can be justified in terms of the principle of beneficence found in the guidelines, but is a central obligation only if the aims of the profession are enlarged to include not only the study of disease but also a commitment to disease prevention. An important issue in womens health--alcohol and breast cancer--provides an illustrative example.

Roles and responsibilities of epidemiologists.

Two distinct views of the roles and responsibilities of epidemiologists have emerged in a decades-long debate: one keeps professional practice constrained to science; the other adds active participation in public health policymaking. In defense of the narrower view are several claims: that epidemiologists lack expertise in policymaking; that advocating policy adversely affects scientific objectivity; that the limits of epidemiologic science work against translating results into policy; and that participation in policy can bring on personal attacks. In this study, each claim is addressed. Epidemiologists already participate fully in educational, research funding, and editorial policymaking and thereby have an experiential foundation in some of the basics of policymaking. Policymaking can enhance scientific objectivity because it requires not only the use but more importantly the improvement of empirical methods. Finally, the comforts of professional life are not the primary yardsticks of our responsibilities. Arguments in favor of active involvement in public health policymaking are presented. Epidemiologists have been mixing science and policymaking for a long time and there is a strong sense that the benefits of public stewardship outweigh the risks. The American College of Epidemiologys Ethics Guidelines support this view. Active participation in public heath policymaking will, however, require curriculum changes in graduate training programs. With additional training and a broader recognition that public health policymaking is an appropriate professional pursuit, epidemiologists can look to a bright and challenging future in the science and practice of public health.

NEW ETHICS GUIDELINES FOR EPIDEMIOLOGY : BACKGROUND AND RATIONALE

In the past decade, at least four sets of ethics guidelines for epidemiologists have been prepared by various national and international organizations. None, however, have been officially adopted by the American College of Epidemiology (ACE). Recently, the ACE asked its Ethics and Standards of Practice (ESOP) Committee to produce ethics guidelines. In this paper, we explain the context and rationale for this effort, describe the purpose and content of ethics guidelines in epidemiology, and discuss their strengths and weaknesses. Three issues that are central to the mission of ACE-education, policy, and advocacy-are inadequately addressed in existing ethics guidelines. In addition, ethics guidelines are not static documents; they should reflect the changing role of epidemiologists in society, including issues arising in emerging subspecialty areas. New, more dynamic, guidelines that emphasize core values, obligations, and virtues, may help to further define and legitimize the profession of epidemiology and will provide a foundation for the discussion of specific ethical issues in the classroom and in professional practice. Guidelines however, do not provide the final word on ethical issues. Specific decisions in particular cases require judgments made upon reflection of the core values, obligations, and virtues described in the guidelines. From our review, we conclude that a new set of guidelines is reasonable and warranted.

Meta-Analysis and Causal Inference: A Case Study of Benzene and Non-Hodgkin Lymphoma

Meta-analysis is an important method in the practice of occupational epidemiology, with a legitimate, but limited role to play in causal inference. Meta-analysis provides an assessment of consistency-one of several classic causal criteria-through tests of heterogeneity and an assessment of differences across studies. It can also provide an increase in the precision of effect estimates, including the precision of dose response relationships. Causal inference, however, involves much more: a complete assessment of the classic causal criteria, for example. Causal claims, therefore, should not emerge from meta-analyses as such. A recent meta-analysis of epidemiological studies of benzene exposure and non-Hodgkin lymphoma (NHL), however, does exactly that. Using studies from a previous narrative review in which the authors made no causal claim, the same authors performed a meta-analysis and concluded that it represented new evidence that benzene causes NHL. Despite a lack of consistency (i.e., significant heterogeneity), weak associations, no evidence of dose-response, no effort to provide an assessment of biological plausibility, and no new epidemiological evidence, the authors, nevertheless, changed their conclusion from association to causation. By using case study as an illustrative platform, this commentary provides cautionary and critical comments about the use of meta-analysis and causal inference in occupational epidemiology.

Abstract 1908: Meta-analysis of prospective epidemiologic studies of red meat intake and colorectal cancer

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FLnnBackground: The relationship between red meat consumption and colorectal cancer (CRC) has been the subject of scientific debate. Objective: To estimate the summary association between red meat intake and CRC and to examine sources of heterogeneity, a meta-analysis of prospective studies was conducted. Design: Thirty-four prospective studies of red meat and CRC were identified, of which, 25 represented independent non-overlapping study populations. Summary relative risk estimates (SRREs) for high vs. low intake and dose-response relationships were calculated. Results: In the high vs. low intake meta-analysis, the SRRE was 1.12 (95% CI: 1.04-1.21) with significant heterogeneity (p = 0.014). Summary associations were modified by tumor site and gender. The SRREs for colon cancer and rectal cancer were 1.11 (95% CI: 1.03-1.19) and 1.19 (95% CI: 0.97-1.46), respectively. The SRREs among men and women were 1.21 (95% CI: 1.04-1.42) and 1.01 (95% CI: 0.87-1.17), respectively. Conclusions: The available epidemiologic data are not sufficient to support an independent and unequivocal positive association between red meat intake and CRC. This conclusion is based upon summary associations that are weak in magnitude, heterogeneity across studies, inconsistent patterns of associations across the sub-group analyses, and the likely influence of confounding by other dietary and lifestyle factors.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1908. doi:10.1158/1538-7445.AM2011-1908