Health is a concept that relates to and describes a person's state of being. It is therefore highly subjective. Good health means different things to different people, and its meaning varies according to individual and community expectations and context. Many people consider themselves healthy if they are free of disease or disability. However, people who have a disease or disability may also see themselves as being in good health if they are able to manage their condition so that it does not impact greatly on their quality of life. People living in areas where there are high levels of ill health, or extreme health problems, may see themselves as relatively healthy, even if they have some illnesses or complaints. And people with relatively minor ailments may perceive themselves to be in poor health if they are aspiring to a greater level of wellbeing than is suggested merely by the absence of disease.
Health is often defined in terms of its negative aspect (e.g. ill-health), and a key focus of the health area of concern is the presence or absence of sickness, disease, injury and disability within the population. However, this is by no means the full story. The World Health Organisation (WHO) definition of health suggests that health is a continuum, and extends the notion of health to include states of positive wellbeing. Health is ‘a state of complete physical, mental and social wellbeing and not merely the absence of disease or infirmity'.1
DIMENSIONS OF HEALTH
This definition also acknowledges that there are a number of dimensions to health - physical, mental and social. Thus the optimal functioning of a person's physical body is only one aspect of their health, and only one factor, in the domain of health, that determines their wellbeing. A person's mental or psychological state is also an important aspect of their health, and the quantity and quality of an individual's social connections and support networks can fundamentally influence their health. Over a lifetime, reserves in one area of health may be drawn on to supplement other areas in difficult times. For example, the physical health deterioration experienced by older people can be partly ameliorated or balanced by positive reserves of mental health, and/or a supportive social environment. Two major dimensions of health - physical health and mental health - are discussed below.
Physical health - Physical health relates to the functioning of the physical body. There are many different diseases, injuries and disabilities that can impair this functioning to a greater or lesser degree. Each of these diseases or disabilities has features and processes associated with it that become relevant to defining the health of individuals or populations affected by them.
Mental health - Mental health relates to people's emotions, thoughts and behaviours. As with physical health, mental health can be impaired to varying degrees. Generally, a person with good mental health is able to handle day-to-day events and obstacles, work towards important goals, and function effectively in society. However, even minor mental health problems can affect everyday activities so that individuals cannot function within their family and community as they would wish to, or are expected to. Over a lifetime, these problems may include day to day anxieties, work-related stresses and normal reactions to adverse life events. However, more serious and long term mental health disorders may be diagnosed in an individual when they reach a specific level of personal dysfunction.
These two dimensions of health - physical and mental - interact with one another. For example, a person's physical health can influence their mental state. People with illness or disability may feel depressed or anxious in relation to their disease or disability, and its implications for their life. More directly, their condition, or their medication, may be associated with chemical changes that influence emotions. Conversely, a person's mental health can influence their physical state. Positive emotions may contribute to a person's ability to recover from disease, while unhappiness, alienation, or the lack of a strong sense of purpose may be factors that make the human immune system more vulnerable to disease. Certainly people's outlook on life can affect lifestyle choices, which in turn influence health status.
FACTORS INFLUENCING HEALTH
In many cases, the reasons why particular individuals contract particular diseases may be unknown. A disease process may begin as a person's physical resources deteriorate with age, or it may emerge at any age with no clear cause. There are, however, a number of factors that appear to influence health outcomes, or play a role in influencing the progress of a disease. Some of these factors are beyond the control of the individual, such as their age, sex and genetic make up. However, many other factors are controllable to some degree, for instance, lifestyle behaviours such as smoking, diet, physical activity and alcohol consumption. The health status of an individual may also be influenced by the social, economic and physical environments in which they live. Factors affecting health can interact with one another. For example, dietary factors may interact with genetic factors to increase the likelihood of someone developing diabetes. As all of these factors can either improve or reduce the health of individuals, they are fundamental to understanding the health status of the population, or of particular groups, and how this can be effectively influenced. Risk factors that can be modified are of particular interest, as they can play an important role in the prevention of ill health in the community.
Overall, the physical health of most individuals will deteriorate over the life course in a relatively predictable way due to the ageing process. However, against this background of slow decline, most people's health status will fluctuate considerably. At a subtle level, people's health may change from moment to moment, or day to day. They are likely to experience bouts of ill-health: many common illnesses are episodic and have a short term impact on people's lives (e.g. influenza, glandular fever, or broken limbs). People may also experience longer-term disability due to diseases such as cancer, clinical depression or diabetes, or resulting from serious injuries. People may change their lifestyle behaviours in response to the ageing process or to conditions they develop, or because their health-related knowledge or attitudes change. Also, the environments and circumstances surrounding an individual will change. People may change jobs or move interstate or overseas, and their family structures will shift, each of these bringing different kinds of stresses and benefits. Importantly, health risk factors can accumulate over a lifetime to increase propensities towards particular health outcomes, including propensities towards specific diseases. Thus an individual's genetic background and their early childhood dietary patterns may affect how healthy they become in later life. Smoking, excessive intake of alcohol, physical inactivity, or even stress and anxiety, can affect not only a person's immediate health, but also their future health outcomes, particularly if sustained over long periods.
Similarly, for many diseases and injuries, the onset of related conditions may be gradual, go unnoticed, or remain undiagnosed for years. Early symptoms might be present but ignored or misinterpreted. Only when symptoms become significant might a condition be identified and appropriate services sought. And disability resulting from a disease or injury can worsen over the years a person lives with it.
For these reasons, a person's health status is not always adequately described by their current diagnostic status. Rather it may need to be considered in terms of their present and past experiences and lifestyle, which can be a guide to underlying health propensities, and future health patterns.
IMPACT OF DISEASE AND INJURY
Even when an individual has been diagnosed with a particular condition, the implications of having that disease will vary according to factors such as the type of illness or injury and the characteristics of the person with the illness. For some conditions, the person would not be expected to live as long as they would without the disease. But, where premature death is unlikely, the extent to which the condition will cause the person suffering and/or result in disability is the main focus of concern. They may be mildly or severely affected, or possibly mildly affected physically, and severely affected mentally, or vice versa. The duration of a condition also will determine the extent to which it affects the lives of those suffering it. Thus concepts relating to severity and duration of disability need to be taken into account in any meaningful definition of the health status of an individual.
Similarly, governments and health researchers need to understand not only which diseases are the major contributors to premature mortality in the population, but which cause the greatest amount of ill health and disability. For example, although depression is not a leading cause of death, it is a leading cause of disability. Using both these measures, an understanding of which diseases represent the greatest burden to the population overall can be achieved. Thus, studies of the burden of disease and injury estimate, for specific diseases, both the number of years of life lost due to premature mortality, and the number of years of healthy life lost due to associated disability. These studies may also incorporate assumptions about the average duration and level of disability associated with specific diseases, compiled to provide population estimates of these. Health risk factors can also be assessed in terms of their contribution to the overall burden of disease for the population. For instance, smoking is associated with a high disease burden, both in terms of the disability it can generate, and in terms of premature mortality.
INTEGRATING HEALTH APPROACHES
The WHO definition quoted above was formulated as far back as 1946, and movement towards viewing health as a dynamic between different aspects of life has gained momentum over the 20th century within medical, statistical and social paradigms. For example, the idea that diseases have a single cause has been gradually replaced with the view that a range of lifestyle and other factors can combine to contribute to disease. Communities and governments have begun to consider health prevention or intervention strategies that draw on broader community areas, such as family and community networks, education, recreation and the arts. There is increasing interest in integrating health services across general practice, community health and local government services. Interest in linking data about social and economic context with mortality rates and other broad level health indicators is also growing.
This movement towards integration, both in terms of understanding health processes and responding to health problems, has paralleled growing interest in alternative and holistic health treatments and approaches. Modalities such as nutrition, massage, meditation, acupuncture, physiotherapy and natural remedies (e.g. herbs) are continuing to grow in popularity, and are seen as allowing practitioners to take a broader approach to improving the health of individuals, and preventing the onset of ill health. In some areas people's health is being considered as a holistic phenomenon - relating to their whole person and context, rather than just to their physical or mental fitness.