Annual Review of Public Health - Volume 18, 1997

Aspirin irreversibly inhibits cyclooxygenase in platelets for their entire lifespan, raising the possibility of clinical benefits by decreasing risks of occlusive vascular events. In secondary prevention among patients with a wide range of prior occlusive vascular events, including myocardial infarction (MI), stroke, transient ischemic attacks (TIAs), as well as unstable and chronic stable angina, aspirin therapy is associated with a reduction in risks of subsequent MI, stroke, and vascular deaths. In acute MI, aspirin also confers clear benefits on subsequent MI, stroke, and vascular deaths. In primary prevention, the available randomized trial data, which to date are limited to men, indicate a clear reduction in risk of a first MI; the current data are inconclusive concerning aspirin's effect on stroke and total vascular mortality. A currently ongoing trial among 40,000 apparently healthy women will provide reliable data concerning the balance of benefits and risks of aspirin in primary prevention.

A greater variety of categorical data methods are used today than 15 years ago. This article surveys categorical data methods widely applied in public health research. Whereas large sample chi-square methods, logistic regression analysis, and weighted least squares modeling of repeated measures once comprised the primary analytic tools for categorical data problems, today's methodology is comprised of a much broader range of tools made available by increasing computational efficiency. These include computational algorithms for exact inference of small samples and sparsely distributed data, conditional logistic regression for modeling highly stratified data, and generalized estimating equations for cluster samples. The latter, in particular, has found wide use in modeling the marginal probabilities of correlated counted, binary, and multinomial outcomes. The various methods are illustrated with examples including a study of the prevalence of cerebral palsy in very low birthweight infants and a study of cancer screening in primary care settings.

A key characteristic that distinguishes survival analysis from other areas in statistics is that survival data are usually censored. Censoring occurs when incomplete information is available about the survival time of some individuals. We define censoring through some practical examples extracted from the literature in various fields of public health. With few exceptions, the censoring mechanisms in most observational studies are unknown and hence it is necessary to make assumptions about censoring when the common statistical methods are used to analyze censored data. In addition, we present situations in which censoring mechanisms can be ignored. The effects of the censoring assumptions are demonstrated through actual studies.

This paper reviews the common statistical techniques employed to analyze survival data in public health research. Due to the presence of censoring, the data are not amenable to the usual method of analysis. The improvement in statistical computing and wide accessibility of personal computers led to the rapid development and popularity of nonparametric over parametric procedures. The former required less stringent conditions. But, if the assumptions for parametric methods hold, the resulting estimates have smaller standard errors and are easier to interpret. Nonparametric techniques include the Kaplan-Meier method for estimating the survival function and the Cox proportional hazards model to identify risk factors and to obtain adjusted risk ratios. In cases where the assumption of proportional hazards is not tenable, the data can be stratified and a model fitted with different baseline functions in each stratum. Parametric modeling such as the accelerated failure time model also may be used. Hazard functions for the exponential, Weibull, gamma, Gompertz, lognormal, and log-logistic distributions are described. Examples from published literature are given to illustrate the various methods. The paper is intended for public health professionals who are interested in survival data analysis.

Cryptosporidium has become the most important contaminant found in drinking water and is associated with a high risk of waterborne disease particularly for the immunocompromised.

There have been 12 documented waterborne outbreaks in North America since 1985; in two of these (Milwaukee and Las Vegas) mortality rates in the immunocompromised ranged from 52% to 68%.

The immunofluorescence antibody assay (IFA) using epifluorescence microscopy has been used to examine the occurrence of Cryptosporidium in sewage (1 to 120 oocysts/liter), filtered secondary treated wastewater (0.01 to 0.13 oocysts/liter), surface waters (0.001 to 107 oocysts/liter), groundwater (0.004 to 0.922 oocysts/liter) and treated drinking water (0.001 to 0.72 oocysts/liter).

New rules are being developed (Information Collection Rule and Enhanced Surface Water Treatment Rule) to obtain more occurrence data for drinking water systems for use with new risk assessment models. Public health officials should consider a communication program to physicians treating the immunocompromised, nursing homes, develop a plan to evaluate cases of cryptosporidiosis in the community, and contribute to the development of public policies that limit contamination of source waters, improve water treatment, and protect public health.

The health hazards due to exposure to environmental tobacco smoke (ETS) are increasingly established. ETS contains thousands of chemicals including 43 known carcinogens. Known health effects of ETS exposure are lung cancer in nonsmokers, childhood disorders such as bronchitis, and perhaps, heart disease. Workplace exposure to ETS is widespread and is influenced strongly by the type of smoking policy in the workplace. To decrease ETS exposure, efforts to restrict public smoking have proliferated over the past decade. These restrictions have emanated from government as well as voluntary measures by various private industries. Bans on public smoking are effective in reducing nonsmokers' exposure to ETS. Workplace smoking bans also influence the intensity of smoking among employees and may increase quit smoking rates. In addition to the health benefits from smoke-free workplaces, there are likely cost savings to employers who implement such policies.

Lead poisoning is the most significant and prevalent disease of environmental origin among US children. Despite over 100 years' knowledge of the special hazards of lead exposure for young children, it has taken over a century for effective primary prevention to be adopted. Obstacles to primary prevention have included deliberate campaigns by industry to prevent restrictions upon such uses on lead as plumbing, paints, and gasoline additives; influence of industrial support of biomedical research at major US medical schools; lack of appropriate policy mechanisms to identify and control lead exposures; and opposition to investing resources in lead poisoning prevention. The removal of lead from gasoline, which began in the United States in 1972 and was completed in 1995, has resulted in almost fourfold reductions in median blood lead levels in US children from 1976 to 1991. Increased screening and interventions to identify and abate lead sources, such as lead in housing, also contributed to this major public health success. Nevertheless, lead exposures remain prevalent, although increasingly less generally distributed. Perhaps because of the renewed “ghettoization” of lead, support for lead poisoning prevention has waned. Objections to investing public and private resources in screening and source abatement have challenged the continuing commitment of public health officials to prevention. The demonstrable success and social benefits of preventing lead toxicity are cited in support of continued preventive health policies.

Organochlorines are a diverse group of persistent synthetic compounds, some of which are detectable in nearly everyone. Many organochlorines are endocrine disruptors or carcinogens in experimental assays. p,p′-DDE (dichlorodiphenyl- dichloroethene) and PCBs (polychlorinated biphenyls) comprise the bulk of orga- nochlorine residues in human tissues. We reviewed relevant human data cited in the 1991–1995 Medline database and elsewhere. High-level exposure to selected organochlorines appears to cause abnormalities of liver function, skin (chloracne), and the nervous system. Of more general interest, however, is evidence suggesting insidious effects of background exposure. Of particular concern is the finding of neonatal hypotonia or hyporeflexia in relation to PCB exposure. The epidemiologic data reviewed, considered in isolation, provide no convincing evidence that organochlorines cause a large excess number of cancers. A recent risk assessment that considered animal data, however, gives a cancer risk estimate for background exposure to dioxin and dioxin-like compounds (e.g. some PCBs) with an upper bound in the range of 10⁻⁴ per year.

The field of environmental health and protection and the entire field of public health have repeatedly found themselves isolated from one another, unable to articulate the definition, mission, and goals of public health and the essential role for environmental health and protection in the provision of a healthy ecological and human environment. Environmental agencies often forget that they, too, are public health agencies; public health agencies that have had environmental health functions have divided and abdicated their environmental responsibilities, considering these to be “regulatory” rather than public health. This article reviews the history of environmental health and protection, its involvement within the field of public health, its eventual separation from other public health programs with resulting benefits and consequences, and what the future may hold for environmental health and protection activities as well as for the broader scope of public health of which these activities are a part.

Efforts to measure public health practice have taken on various forms and focused on different aspects of the system of public health practice over the past century. Before 1990, measurement was primarily based on a series of self-assessment instruments initiated under the auspices of the Committee on Administrative Practice of the American Public Health Association. These instruments emphasized measurement of immediate results of local public health services although they also provided information on local resources and capacity to perform. Following the Institute of Medicine's report in 1988, efforts began to focus on performance related to public health's core functions. These more recent assessments suggest that the system of public health practice must be improved to achieve the targets of effectiveness established for the year 2000. Ultimately, a comprehensive national surveillance system for public health practice will need to both measure and examine the relationships among inputs (resources, capacity, etc), core function–related processes, outputs (services) as well as outcomes.

Populations affected by armed conflict have experienced severe public health consequences mediated by population displacement, food scarcity, and the collapse of basic health services, giving rise to the term complex humanitarian emergencies. These public health effects have been most severe in underdeveloped countries in Africa, Asia, and Latin America. Refugees and internally displaced persons have experienced high mortality rates during the period immediately following their migration. In Africa, crude mortality rates have been as high as 80 times baseline rates. The most common causes of death have been diarrheal diseases, measles, acute respiratory infections, and malaria. High prevalences of acute malnutrition have contributed to high case fatality rates. In conflict-affected European countries, such as the former Yugoslavia, Georgia, Azerbaijan, and Chechnya, war-related injuries have been the most common cause of death among civilian populations; however, increased incidence of communicable diseases, neonatal health problems, and nutritional deficiencies (especially among the elderly) have been documented. The most effective measures to prevent mortality and morbidity in complex emergencies include protection from violence; the provision of adequate food rations, clean water and sanitation; diarrheal disease control; measles immunization; maternal and child health care, including the case management of common endemic communicable diseases; and selective feeding programs, when indicated.

The safety of food has been an age-old concern. Early civilizations adopted laws that punished sellers of tainted food. In this country, before food safety became a responsibility of the federal government every state had enacted laws prohibiting the sale of food that contained poisonous substances. The modern scientific and legal instruments available to the US Food and Drug Administration and allied agencies have improved regulation and advances in food preparation, preservation, and storage have contributed to a safer food supply. Even so, some observers believe that contemporary threats to food safety have grown more serious, and they surely excite intense public concern. For nearly two decades Congress has been debating the adequacy of current laws governing food safety. In the closing months of the 104th Congress, both parties finally agreed on the first significant legislative change in over a generation. This chapter examines the origins of the issues that were the focus of this extended debate and analyzes the implications of their resolution.

Increasing social inequalities in health in the United States and elsewhere, coupled with growing inequalities in income and wealth, have refocused attention on social class as a key determinant of population health. Routine analysis using conceptually coherent and consistent measures of socioeconomic position in US public health research and surveillance, however, remains rare. This review discusses concepts and methodologies concerning, and guidelines for measuring, social class and other aspects of socioeconomic position (e.g. income, poverty, deprivation, wealth, educattion). These data should be collected at the individual, household, and neighborhood level, to characterize both childhood and adult socioeconomic position; fluctuations in economic resources during these time periods also merit consideration. Guidelines for linking census-based socioeconomic measures and health data are presented, as are recommendations for analyses involving social class, race/ethnicity, and gender. Suggestions for research on socioeconomic measures are provided, to aid monitoring steps toward social equity in health.

The advent of reversible long-acting contraceptives–IUDs, injectables and implants–has provided women throughout the world with valuable new fertility regulation options. These highly effective methods, together with male and female sterilization, have proven to be enormously popular and are now used by the majority of women and men who are currently contracepting worldwide.

Despite their remarkable popularity, long-acting contraceptives have engendered considerable controversy. Political, ethical, and safety questions have emerged, stemming from the ways in which these contraceptives have been developed and used over the course of this century. At the heart of the concern is the issue of reproductive rights and freedom.

This paper reviews the history of the development of long-acting contraceptives, including the prospect of new methods that will likely emerge from ongoing research and development. It also examines the history, in the United States and in developing countries, of the use and abuse of long-acting methods, including sterilization, in the context of eugenics and population control policies. It then describes a new paradigm of reproductive health and rights that has emerged from the International Conference on Population Development in Cairo, and which offers an enlightened approach to future policies and programs.

In light of the wide variety of ways in which long-acting contraceptives have been provided, the paper examines the rights and responsibilities of governments, family planning providers, and individuals. An ethical framework for the use of long-acting methods is discussed, and public policies for the future are proposed.

Social inequalities lie at the heart of risk of HIV infection among women in the United States. As of December, 1995, 71,818 US women had developed AIDS-defining diagnoses. These women have been disproportionately poor, African-American, and Latina. Their neighborhoods have been burdened by poverty, racism, crack cocaine, heroin, and violence. To explain which women are at risk and why, this article reviews the epidemiology of HIV and AIDS among women in light of four conceptual frameworks linking health and social justice: feminism, social production of disease/political economy of health, ecosocial, and human rights. The article applies these alternative theories to describe sociopolitical contexts for AIDS' emergence and spread in the United States, and reviews evidence linking inequalities of class, race/ethnicity, gender, and sexuality, as well as strategies of resistance to these inequalities, to the distribution of HIV among women.

Population-based, person-specific health surveys, with concomitant biological measures, should provide important information about the processes by which socioeconomic and psychosocial factors embed themselves in human health. Questionnaire responses allow for assessment of the perceived psychosocial environment, but biological measurements will measure the status of the psychoneuroimmunology/psychoneuroendocrinology (PNI/PNE) pathways and may allow us to identify people who have “adapted” to their stress because of experience, expectations, stoicism, etc. This review sets criteria to evaluate potential physiological markers of chronic stress. Because population health surveys involve a massive number of samples, special consideration must be given to the laboratory analysis method and transportation time of the markers chosen. We reviewed five areas: glycosylated proteins, the immune system, hemostasis, peripheral benzodiazepine receptors, and the waist-hip ratio.

Poverty has been shown to negatively influence child health and development along a number of dimensions. For example, poverty–net of a variety of potentially confounding factors—is associated with increased neonatal and post-neonatal mortality rates, greater risk of injuries resulting from accidents or physical abuse/neglect, higher risk for asthma, and lower developmental scores in a range of tests at multiple ages.

Despite the extensive literature available that addresses the relationship between poverty and child health and development, as yet there is no consensus on how poverty should be operationalized to reflect its dynamic nature. Perhaps more important is the lack of agreement on the set of controls that should be included in the modeling of this relationship in order to determine the “true” or net effect of poverty, independent of its cofactors. In this paper, we suggest a general model that should be adhered to when investigating the effects of poverty on children. We propose a standard set of controls and various measures of poverty that should be incorporated in any study, when possible.

Increasing concern about the state of basic and clinical research in England during the 1980s led to an influential parliamentary review. Surprisingly, the review recommended the strengthening of public health and health services research through the establishment of a research and development (R&D) program for the National Health Service (NHS). The program that started in 1991 was unique in that it was fully integrated into the management structure of the NHS. No country had ever attempted such an ambitious approach.

While a review of the first five years of the program reveals many achievements, it also raises several concerns: Debate about the philosophy and aims of the program continues; the need to maintain political support requires constant attention; policy changes in other areas need to be accommodated; central control of a national, coordinated R&D program has to be guarded; methods of priority setting need to be enhanced; insufficient human resources to run the program have to be contended with; and the program needs to be rigorously evaluated.

Other countries with a unified health system could learn much from the English experience. Countries with pluralist systems might benefit from specific parts of the experience.