The Mortality Shift that began in the 1850s and continues to this day in the industrialized world is marked by a constant increase in life expectancy at birth. For many centuries, life expectancy was about 35 years, while today it is between 77 and 85 years and rising in almost all industrialized countries. The table below is an example drawn from available data that shows the changes in life expectancy in the United States, Canada and the United Kingdom over the last 90 or so years despite depression and war.
The explanation for this change is still being debated. I will review three of the main positions.
- Increased life expectancy is primarily due to medical science
- The increase is due to advances in public health
- The increase is due to a complex interaction of many factors, primarily non-health
Each of these explanations has had a strong successive influence on health policy over the last century. In all of them life expectancy at birth has stood as a surrogate for the health of a population. The three views state that the changes are due to medical science, to public health and to a broad range of determinants of health. Let me briefly describe each of them.
Scientific Medicine Results in a Healthier Population
A strong argument was made for the impact of medical science on population health. Many histories of medicine have claimed that the major scientific advances in medicine in the 19th century resulted in the dramatic reduction of surgical mortality through the introduction of ether in the 1850s, and the promotion of sterile operating environments by Joseph Lister in the 1860s. These innovations also helped to reduce infant and maternal mortality through more scientific childbirth with fewer infections, for both mothers and infants. The discovery of the causes of infectious diseases by Robert Koch and Louis Pasteur led to the development of vaccines that saved the lives and increased the longevity of large numbers of children. Finally, the introduction of penicillin and its widespread use during World War II confirmed the incredible contribution of medicine to a healthier and longer lived population.
The successes of scientific medicine in the late 19th century was probably the greatest influence in the development of our current healthcare systems which are built around hospitals, medical schools and research facilities.
Better Public Health is the Main Basis for a Healthier Population
The Miasma Theory of Illness was the theoretical frame for the Sanitarian movement led by Edwin Chadwick. It was falsely believed that foul smelling air and dirty water contained pollutants that caused diseases like cholera, typhoid fever, and even the Plague. Chadwick devoted a good part of his life to improving sanitary conditions in England, and in 1848 he succeeded in getting the first public health act passed in England. This was followed by the construction of new sewer systems for London and other cities in the late 1850s, and the passage of a much stronger public health act in 1875. Many current public activities like the development of policies related to food inspection and labelling, anti-smoking legislation and so on are in that tradition.
Advocates for increased public health have argued that these and other public health measures were more responsible for a healthier longer lived population than medical interventions. This view was one of the bases for the Lalonde Report which led to great changes in public policy and population behaviour in the 1970’s and later. Today, many argue with some justification that anti-smoking legislation has had a greater impact on the reduction of cancer and heart disease than the billions of dollars spent on medical research.
The Social Determinants of Health Argument
More recently scholars of the Mortality Shift have argued that the most cogent explanation for the great increase in life expectancy was that the period that began in 1850 was one where general prosperity led to increased earnings and better living conditions for large numbers of people in the developed world. Although medical care and public health measures did contribute to a healthier population, both were less critical than improved housing, better working conditions increased education and similar factors that resulted in people living longer.
Advocates for the social determinants of health view argue that there is good evidence that tuberculosis was decreasing as a result of less crowded housing well before medical intervention began, and that the reduction of mother and infant mortality was on the decline because of better maternal nutrition. Holders of this view also believe that healthier populations have greater income equality. In many countries income disparity was reduced during the period of increasing life expectancy. However, income inequality has been increasing for the last 40 years without any reduction in life expectancy. Many who hold this view are beginning to think that life expectancy at birth may not be such a good surrogate for the health of a population.
My next blog will focus on how our health care system came to be.