A Healthy Early Childhood = A Healthy Adult Life

.	. A Healthy Early Childhood = A Healthy Adult Life .
	.

We have known for a long time that there is a strong connection between the environment in which each of us lives and works throughout our lives and our health and well-being. Only recently have we developed a better understanding of the pathways through which the environment influences our health. Improving this understanding has been one of the principal objectives of the CIAR's program in Population Health.

One of the important clues as to why some people are healthier has come from the work of Michael Marmot and his colleagues at the International Centre for Health and Society University College, University of London.

They have studied the health outcomes of the Whitehall civil service in London over the past two decades. These individuals living and working in London are relatively well educated, well housed, well fed and reasonably well paid. These British civil servants live in a society where there have been no financial barriers to medical care since 1948. In other words, it is a reasonably economically secure middle-class population working at tasks that are largely non-manual. Thus, differences in the health of these civil servants reflect factors that contribute to differences in health across a typical middle-class population.

One of the important findings is the relationship between the mortality rates of people and their job status - in other words, that death is a gradient when measured against job classification. The top tier of British civil servants had the fewest deaths while the bottom tier had the most deaths during the study period [the data are adjusted for age and sex].

One possible explanation for the gradients was that individuals in the top tier adopt a healthier life style than individuals further down the career ladder. Yet, while differences in life style make some difference in the health of individuals, a second striking observation from these studies is that the gradient in deaths is true for most of the major causes of death, including death from cardiovascular diseases, such as strokes and heart attacks, cancer [smoking and non-smoking related], accidents, and suicides. The gradient also holds true for absence from work because of sickness. So what are the conditions in the environment in which British servants work and live that links their vulnerability to disease to where they are in the job hierarchy? Why are bosses healthier than the clerks by these measures?

One clue about the possible explanation or pathways can be found in the analysis of coronary heart disease among male British civil servants. For a male under the age of 55, the risk of dying from a heart attack is four times greater if he is in the bottom tier of the job hierarchy than if he is in the top tier. Less than 25 per cent of the gradient in deaths from coronary heart disease across the different grades could be explained by conventional medical risk factors, such as cholesterol, smoking and high blood pressure.

A Swedish study provides some insight into how job status affects the health of individuals in relation to coronary heart disease. It found that fewer than three per cent of individuals who considered their job to be high demand and had a high degree of control, showed signs of coronary artery disease, while 20 percent of individuals in high-demand jobs with low control had coronary disease symptoms. This technique of looking at the psycho-social characteristics of work and health was applied to the British civil service with similar results. More recently, measures of the balance between effort and reward at work has been shown to be associated with health risks. Evidence indicates a relationship between how well an individual copes with his or her job - a measure of the degree of stress in a job - and the health of that individual.

If health, as measured by death, shows a gradient, then it is also likely that health, as measured by absence from work due to sickness, is also a gradient. Again, the sickness absence rate in the British civil service shows a clear gradient when measured against job hierarchy. A common cause of sickness absence among these largely non-manual workers consisted of back pain and other musculo-skeletal disorders, raising the question as to why there should be a gradient in conditions such as back pain among non-manual workers.

The explanation for these gradients in health involves the pathways that determine the biological processes that can influence cells, tissues, and organs in the human body, such as muscle tissues, arteries and the brain.

We know that how well individuals cope with the environments in which they live and work is strongly influenced by their cognitive and behavioural characteristics. Research in developmental neurobiology and the linkages between the brain, the endocrine pathways, and components of the body's host defence systems, such as the immune system, is providing important insights into the biological pathways that affect well-being and disease expression and how these pathways are influenced by how individuals cope with the environment in which they live and work.

The competence and coping skills of all of us are influenced by the factors that shape the development of our brain in the earliest years of our lives. The billions of neurons in our brain require stimulation to differentiate for their various functions and to develop their full functioning capability.

The critical period for the development of the core components of the brain is in the first years following birth. Our coping skills appear to be strongly influenced by how well we are "nurtured" during those early years of childhood. Failure to properly shape the "architecture" of the brain in the earliest years of life has a profound effect on coping skills in adult life.

Individuals who do not cope well with the conditions of their work environment for example, can find their health damaged as a result. In a stressful situation, the endocrine system in our bodies takes over, releasing key hormones of the stress response linked to steroids into our bodies. In a person with good coping skills, the endocrine system quickly returns to equilibrium following stress. But individuals with poor coping skills find their endocrine system does not come back into equilibrium quickly, a situation which is made much worse when stress is sustained. This leads the body to sustain high levels of steroid hormones, such as cortisol, which can depress the immune system, leading to increased risk of ill health. Persistently high levels of steroids can also affect the brain, killing neurons in the hippocampus, with adverse effects on the coping skills of individuals.

The studies by Marmot of British civil servants have found that the biological systems of those in the top tier behave differently from the biological systems of those in lower tiers. The blood pressure of all civil servants, regardless of where they stand in the job hierarchy, rises when they go to work. But, at home, the blood pressure of individuals in the top tiers tend to drop while in the bottom tiers, blood pressure remains elevated. This suggests that the circumstances for individuals in the top tiers are better than individuals in the lower tiers, and that the home environment is also important. More recent research supports these conclusions. Research in other countries, including Canada, has shown that the gradients in health for British civil servants, depending on their job status, is found in other organizations and for entire societies.

One of the implications of this new understanding of why some of us are healthier than others is that many of the risks for the diseases of adult life are, in part, shaped by competence and coping skills that are set in the earliest years of life. This is shown in British longitudinal studies which have tracked the subsequent experience of children born 30 to 40 years ago and the relationship between socio-economic circumstances in which children were born and their health status as adults.

The analysis of the 1958 British birth cohort show that at age 33, there is a clear gradient in mental health problems, self-rated health, and respiratory disorders, depending upon social class at birth. The 1948 British birth cohort has allowed an analysis of the relationship between early childhood experience and health and employment in adult life. Early life experiences were found to strongly influence unemployment in adult life. At the same time, unemployment is known to have an adverse effect on the health and well-being of individuals.

As a result of all of this research, there is now much more interest today in importance of experience in early life and how this affects the competence and coping skills of individuals in adult life, which in turn influences their health and well-being. What this means for public policy is that efforts to change the experiences in early life can enhance competence and coping skills in adult life, leading to healthier societies. Another implication is that the coping skills of individuals has to be taken into account in setting up the work environment and this has implications for the economy.

Countries, regions, and communities with socio-economic policies that try to sustain cohesion in the environment in which people live and work, including providing the early life "nurturing", have shallower gradients in health than countries, regions and communities that lack the culture or policies that help shape the quality of the social environment.

Sweden and Japan are two countries that have impressive health outcomes. The Swedish health gradient is remarkably shallow, compared to the British health gradient, and the mortality rate for the bottom social class in Sweden is actually lower than that for the top social class in Britain. This has an economic consequence because the competence, coping skills and health and well-being of a population is an important factor in economic growth. The steepness of a country's health gradient is an indicator of how well its economy is working and has implications for the future.

Recent research in Winnipeg demonstrates the existence of clear health gradients by economic conditions in that city. The Winnipeg study shows that the gap in life expectancy between males living in the most affluent neighbourhoods and those living in the poorest neighborhoods is more than eleven years. This is not due to a lack of health services. It is an important reminder to Canadians that to improve the equity in the health of the population, we have to pay more attention to the determinants of health.

The health gradients in a country, region or community, and the workplace, are powerful measures of how the socio-economic forces of society are operating. These gradients in health give us a much better understanding of the determinants of health and of the importance of how changes in the social dynamics of society can improve the overall health and well-being of a nation's citizens.

Clyde Hertzman is a member of the Department of Health Care and Epidemiology at the University of British Columbia and associate director of the CIAR Population health program.

Fraser Mustard is a Bell Canada Fellow and founding President of CIAR.

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Doc Info

Subject (s)	Early childhood -- Health gradients
Doc Type	Article	Date	03/01/1997
		Language	English
Author (s)	J. Fraser Mustard	Access scope	Public
		Cataloguing	Catalogued
		Doc #	fn-ent-4