4- the determinants of morality
For most of human history, life expectancy has been short— approximately 25 years for our ancient ancestors, and only 37 years for residents of England in 1700. In just the past century, however, life expectancy has increased by over 30 years.
Dramatic changes began in the 18th century. Life expectancy in England rose to 41 years by 1820, 50 years by the early 20th century, and 78 years today. A similar shift took place in all developed countries. The drop in mortality rates was particularly radical among children (Figure 1). This was because of the near eradication of deaths from infectious diseases- formerly the most common cause of death, since the young are most likely to get infections.
The most important aspects of daily life that affected mortality reduction were nutrition, public health measures, and medicine.
The history of mortality reduction is spoken of in terms of three phases. In the first phase, from cities, urban centers started to deliver clean water (Figure 2) and remove waste. With the improved water supply, sewage, and general personal hygiene, there was a dramatic reduction in water- and food-borne diseases—typhoid, cholera, dysentery, and tuberculosis.
The third phase, from the 1930s to now, is the time of big medicine. It started with vaccination and antibiotics, and has moved on to a variety of expensive and intensive treatments and procedures.
Looking across countries, there are great differences in life expectancy (Figure 3). There are also sharp differences in who dies and from what. Deaths among children account for approximately 30 percent of deaths in poor countries but less than 1 percent of deaths in rich countries. Most deaths in rich countries are from cancers and cardiovascular disease, white most deaths in poor countries are from infectious diseases.
Though differences persist, many poorer countries have recently experienced large improvements in life expectancy. In India and China, life expectancy has risen by 30 years since 1950. Even in Africa, life expectancy rose by 13 years from the early 1950s until the late 1980s, when the spread of HIV/AIDS reversed the trend.
What factors explain this outcome? Some of the main factors are changes in income, literacy (especially among women), and the supply of calories. Public health interventions, such as immunization campaigns, improvements in water supply, and the use of antibiotics, have also made a big difference.
Although the connection between economic growth and improved health seems stralghtforward, the empirical evidence for this is not completely clear. This may be because urbanization1 often goes along with growth. Growth must be accompanied by effective public health measures in order to bring about mortality reductions.
Within developed countries, there are well-documented differences in mortality rates by race, income, education, occupation, or urban/rural status. There is a definite hierarchy to healthiness—the higher the socioeconomic status of a group, generally the lower the mortality rate. Some explanations for this include definite differences in access to medical care, in access to the resources needed to buy food and shelter, in health- related behaviors such as smoking, and in levels of "psychosocial stress."
The link between social status and health is likely not due to any Isolated factor. Education, however, seems to have a positive effect on health. This may be due to increased knowledge about health and technology.
Is there a universal theory of mortality that can explain improvements over time, differences across countries, and differences across groups? It can be argued that knowledge, science, and technology are important aspects of any logical explanation. As for the future, an increase in the production of new knowledge and treatments is likely to increase inequality in health outcomes in the short term. The silver lining, though, is that help is on the way, not only for those who receive it first, but eventually for everyone.
