At the core of epidemiology is the use of quantitative methods to study health, and how it may be improved, in populations. It is important to note that epidemiology concerns not only the study of diseases but also of all health-related events. Rational health-promoting public policies require a sound understanding of causation. The epidemiological analysis of a disease or activity from a population perspective is vital in order to be able to organize and monitor effective preventive, curative and rehabilitative services. All health professionals and health-service managers need an awareness of the principles of epidemiology. They need to go beyond questions relating to individuals to challenging fundamentals such as ‘Why did this person get this disease at this time?’, ‘Is the occurrence of the disease increasing and, if so, why?’ and ‘What are the causes or risk factors for this disease?’

Public health cannot be understood or fully appreciated without some knowledge of its history, which this Introduction provides. Conventionally, this begins with the large body of work associated with Hippocrates (c. 460–370 BC). In these writings, health was viewed as resulting from a sound balance of the humours. Therapy included diet, exercise and other interventions tailored to the individual – akin to today’s emphasis on healthy living and lifestyle. The Hippocratics were, in addition, early exponents of environmentalism. In Airs, Waters, Places, the occurrence of disease was linked to such factors as climate, soil and water quality. Proposals for disease prevention were related to specific social and economic circumstances.

Health-care systems within most countries are resource-limited – budgets are finite and not every service one would like to provide can be funded. In publicly funded health systems, those responsible for procuring health-care need to be able to explain how taxpayers’ money has been spent. Decisions are made at both individual patient and population levels. At an individual level, the decision might be: which statin should this patient get a prescription for to lower her blood cholesterol? At a population level, the decision might be: will a health and social care commissioning organization purchase a heart-failure specialist nurse or an additional sexual health clinic?

This chapter focuses on how such decisions are made and considers a framework for priority setting, a discussion of what factors should be taken into account when comparing options, a consideration of basic health economic concepts, and an overview of ethical principles which influence decisions.

Effective health-care makes a large and increasing contribution to preventing disease and prolonging life by reducing the population burden of disease. However, only the right kind of health-care delivered in the right way, at the right time, to the right person can improve health. Health-care interventions that are powerful enough to improve population health are also powerful enough to cause harm if incorrectly used. How can public health specialists know whether their interventions are having the desired effect? Clinicians can monitor the impact of their treatments on an individual patient basis, but how do we examine the impact of a new service? This chapter looks at what we mean by quality of health-care and considers some frameworks for its evaluation.

The first element of understanding how to improve the health and well-being of a population relies on a thorough assessment of the needs of the specified population, be it a local population defined by geography, a specific age group or those with certain characteristics. This chapter begins by considering how ‘health need’ can be conceptualized; the distinction between need, demand and supply; and the difference between health needs and the need for health-care. Secondly, the wider determinants of health are introduced and their relation to health needs discussed. Finally, the steps involved in a systematic assessment of the health needs of a defined population are explained, including tools and resources used to achieve this. Practical challenges are considered.

This chapter focuses on the interplay of health policy and politics at a national level, and:

• explores the process by which health policy is created and the context in which it is developed and influenced;

• considers the interplay between policy and its implementation; and

• offers a narrative of the evolution of national health policy and politics in England over the last 30 years.

How much of what health and other professionals do is based soundly in science? Answers to the question, ‘Is our practice evidence based?’ depend on what we mean by practice and evidence.

The expansion of evidence-based medicne (EBM) has been a major influence on medical practice over the past 25 years. In this chapter, we examine the nature of what is nowadays more broadly referred to as evidence-based health-care (EBHC) and discuss its limitations. It is worth noting that in the UK this field continues to expand, particularly into the arena of social care, which often goes hand in hand with the provision of health-care. Increasingly, the term ‘evidence-based practice’ (EBP) is used as a catch-all. While this chapter focuses on health-care, the principles of EBP we describe apply equally to other disciplines, including public health and policy.

As we discussed with regard to leadership in Part 1, the context in which the public health tools are used has a bearing on the choice of tool and how it is implemented. In the second part of Essential Public Health: Theory and Practice, we consider a range of contemporary contexts in which public health is practised and illustrate how the tools we have described are applied.