Epidemiology of non-communicable diseases : a collection of published papers presented in application for the degree of Doctor of Science at Massey University

Abstract

The scientific publications contained in this thesis represent more than 20 years of work in the epidemiology of non-communicable disease. Chapter 1 includes methodological papers that are relevant to non-communicable diseases and epidemiology in general. This work falls into four main areas. Firstly, several papers discuss the analysis of epidemiologic studies. These particularly involve work that I did in the 1980s on the analysis of cohort studies, particularly involving time-related factors. At that time, there were well-established methods for analysing case-control studies, but the analysis of cohort studies was less developed, and there were few programmes or analytical approaches available for taking time-related factors into account. More recently, I have published on epidemiologic concepts of interaction and the implications for approaches to data analysis. Secondly, two papers from the 1980s discuss the epistemological basis of epidemiologic research. At that time, the leading textbook of epidemiology advocated a Popperian approach to the philosophy of science. These papers discussed the limitations of the Popperian approach, and showed that the actual practice of epidemiologists was more consistent with alternative approaches to the philosophy of science. Thirdly, several papers discuss the principles of epidemiologic study design. My contributions particularly involve the theory and practice and case-control studies, and the demonstration that these do not involve "backwards causality" or a radically different study design to that used for cohort studies. Finally, in recent years I have played a major role in an ongoing debate on the future of epidemiology, and published a series of papers on the need for epidemiology to rediscover the population perspective and to use theories and methods that take the population context into account. Chapters 2-5 then include substantive studies of these particular public health issues, as well as more specific methodological papers arising from these studies. My early interest was in occupational and environmental health, with a particular emphasis on cancer, and this work is included in chapter 2. This work falls into three major areas. Firstly, my methodological work particularly includes the textbook of occupational epidemiology published by Oxford University Press in 1989, which I co-authored. This also produced a series of papers on the theory, practice, and teaching of occupational epidemiology. Once again, it particularly involved the analysis of cohort studies, and the design of case-control studies for the specific situation of occupationalhealth research. Secondly, my occupational cancer work has particularly included studies of cancer in farmers and related occupations. These studies were the first to show that meat workers have an increased risk of some types of cancer. This work has also included the firstoccupational cancer cohort study in New Zealand, which examined cancer risk in nuclear test veterans. Finally, I have also studied the particular issues of occupational cancer in developing countries, and the more general issues of environmental change and human health. Chapter 3 includes papers on socio-economic determinants of health, with a particular emphasis on non-communicable disease. In the 1980s I conducted the first studies of socio-economic differences in health and life expectancy in New Zealand. Since the first publication in 1983, at a time when there was little interest in this field of research, this has grown to become a major area of research in New Zealand. My work in Māori health has involved assisting the work of the late Professor Eru Pomare and others in documenting and discussing the causes of differences in health between Māori and non-Māori in New Zealand. This included the first studies to show that the high mortality rates in Māori were not solely to due to socio-economic factors, but also represented problems of access to health care for Māori. Chapter 4 covers studies of asthma mortality, particularly the studies of the role of fenoterol in the New Zealand asthma mortality epidemic of the 1970s and 1980s. These studies were the first to identify that the beta agonist fenoterol was responsible for an epidemic of asthma deaths in New Zealand. These studies were highly controversial, and were strongly criticised, but eventually the New Zealand Ministry of Health restricted the availability of fenoterol in New Zealand and the asthma death rate immediately fell by one half. Unlike the other chapters in this thesis, the work described in this chapter was more clearly done as part of a group, rather than by myself as an individual. The group included an epidemiologist (myself), a clinical research, respiratory physician and a pharmacologist. Inevitably with such a multidisciplinary approach the authorship was variable, although I played the major role in the design and analysis of the epidemiological studies. I have included several review papers since they give an overview of research in this area, and the relative contribution of my own studies to the development of this debate. Finally, chapter 5 includes studies on the prevalence, causes and management of asthma, as well as related methodological work. This work falls into four main areas. Firstly, I have produced a textbook of asthma epidemiology, published by Oxford University Press. This has involved a substantial amount of work in developing the theory and practice of epidemiology in the context of asthma. This is a relatively new field, since asthma is a non-fatal chronic disease that is difficult to diagnose, and asthma studies usually involve prevalence rather than incidence or mortality. This work has led to a number of review papers on asthma epidemiology methods. Secondly, I have been heavily involved in the development of the International Study of Asthma and Allergies in Childhood (ISAAC). Phase I of the study involved more than 700,000 children in 155 centres in 60 countries, and Phase III is currently in progress. Thirdly, in more recent years my research has focussed on the primary causes of asthma, and particularly on the role of non-allergic mechanisms. In addition to specific studies on environmental and occupational causes of asthma, I have published a series of reviews and commentaries that question the importance of allergic mechanisms for asthma. This series of papers is becoming increasingly influential in re-orienting asthma research towards a greater interest in non-allergic mechanisms. My current research interests focus on studies of these mechanisms.