Chapter 10: Disease and Death (Cont)

The diseases of industrialization and urbanization

From the late 18^th century there was a wave of rapid population growth, industrialization and urbanization in western Europe and North America. The environment that these changes produced resulted in a wave of new diseases. One of the most important was tuberculosis, which seems to have shifted from its lymphatic form, common in the previous centuries, into the much more deadly tubercular form.

It was not a major problem until the 19^th century when there was growth of cities and the development of large slums with people existing on poor diets and living in grossly overcrowded conditions.
Not all who are infected develop the disease and its main impact is on the malnourished living in damp conditions.
It was the main cause of urban death in 19^th century Europe and North America.
The effects of poor diet available to most people who lived in the growing urban conurbations of the emerging industrialized world were compounded by the huge palls of smoke from industry and the burning of coal in factories and in the home that cut out much of the sunlight. This produced an epidemic of a deficiency disease known as rickets.
It was the insanitary conditions of the cities in the industrializing world that produced a formidable epidemic that caused fear amongst both rich and poor – cholera.
Death rates were high because of lack of effective sanitation systems – sewage and drinking water intermingled freely.
It was the impact of cholera that slowly forced governments across Europe and North America to construct proper water-supply and sewage treatment systems.
Ever since the early 19^th century there have been waves of cholera that have swept across the world.
The 7^th and latest cholera pandemic began in Indonesia in 1961, spreading to India, Iran, Iraq, the Soviet Union, west Africa and by 1991 it could be found in Latin America.
It remains prevalent in areas with poor sanitation and where public health systems break down under the strain of war and civil war.
It has largely been eliminated in the wealthy, industrialized world.

The role of environmental and medical improvements

In the last century and a half there has been a remarkable transformation in the pattern of human disease that had been prevalent for several millennia. For most of human history a majority of children died within a few years of birth. Now in the rich, developed world only about 1% of children fail to reach the age of 5 and those that do die usually suffer from rare, inherited disabilities. Life expectancy at birth has increased dramatically from between 30 and 40 years at the end of the 18^th century to well into the 70s today. Death rates have fallen steadily. In the 1840s in England about 20 per 1,000 of the population died every year – current rates are about a quarter of that figure. Although the timing of these changes varied from country to country (and there are still differences between them) the overall pattern is similar.

The main reason that people are living longer is that far fewer are killed by the infectious diseases that were the scourge of human history for thousands of years.
Some diseases appear to have evolved over time into less virulent forms. Another key factor is advances in medical knowledge and treatments.
Vaccination eliminated smallpox as a disease and controlled diseases such as measles and yellow fever even if it could not eliminate them.
Apart from vaccination the most important medical advance was the development of antibiotic drugs in the mid-twentieth century.

The impact of medical advances played an important but limited part in the reduction of disease in the industrialised world. Of far greater importance were a better diet and environmental improvements. Public health measures were crucial – effective sewage systems and treatment of drinking water drastically reduced the impact of water-borne intestinal diseases such as dysentery and cholera. Overall about a fifth of the reduction in mortality levels in the 19^th century came from these programmes. A better diet in Europe as more food became available, and better housing (which reduced overcrowding, damp and poor ventilation) also improved resistance to disease.

The mortality pattern of the industrialized world in the 19^th and early 20^th centuries was not repeated in the developing world in the 20^th century. Here the reduction in mortality rates was far greater and quicker.
This partly reflected the appalling conditions of the early 20^th century when average life expectancy was about 25 years at birth (about half that of western Europe and North America). By the late 20^th century this had more than doubled to 63 years.
This was the result of the importation of advanced medical techniques, vaccination, antibiotic drugs and the chemical spraying of mosquito breeding grounds.
By the last third of the 20^th century the fall in the death rate slowed and in some countries went into reverse. This reflected the limits of medical intervention in the face of major social, economic and environmental problems – malnutrition, poor water supply and sanitation and the rapid growth of slums as the urban population rose swiftly.
The result was a huge disparity in the impact of disease and death between the rich and poor countries.
The impact of medical improvements was also limited in dealing with some of the endemic diseases of the poorest countries.

The new infectious diseases

In the late 20^th century a range of ‘new’ infectious diseases emerged, primarily in Africa. The rapidly rising population and the consequent demand for new agricultural land meant that settlements pushed further into tropical forests. This had long been the source of human diseases (for example yellow fever) as infections once confined to monkeys and other primates could jump across the species (as so many had done in the past) to infect humans. It is here that the most devastating of the new diseases – AIDS – spread from chimpanzees (where it had been endemic) to humans somewhere in West and Central Africa probably in the 1920s – the first case can be identified in Kinshasa in 1930. It did so almost certainly through hunting and eating of the animals. It became more widespread during the Angolan civil war of the 1970s and 1980s, reaching South Africa and eventually the whole world.

AIDS has become the greatest of the modern plagues and only the fact that it kills people slowly has lessened its impact on public consciousness – in some places death rates are as high as during the Black Death in Europe.
The disease is, like so many others, a disease of poverty. It is overwhelmingly concentrated in Africa where there are over 25 million people infected – over 7% of the population of sub-Saharan Africa.
In Botswana and Swaziland about 40% of adults have the disease. Life expectancy is falling dramatically in these countries and by 2010 there will be about 20 million children in sub-Saharan Africa who have lost both parents to the disease.
The other new diseases that emerged in the late 20^th century were the group known as haemorrhagic fevers. The first to emerge in 1969 was Lassa fever. Its natural carrier is a mouse but the virus is highly virulent when it crosses to humans, with a death rate of up to 60% through internal bleeding.
A similar disease that causes death through massive internal bleeding is Ebola, first identified in 1976 in western Sudan and the Congo.
The third disease is hantavirus, first identified in China 1,000 years ago and spread to southern United States in the early 1990s where it took a new form.

The diseases of affluence

The major decline in infectious diseases in the industrialized world in the last two centuries has been paralleled by the rise of new diseases that have radically altered the way of death for this minority of the world’s population. High infant mortality and early death from infectious diseases have been replaced by cancer and cardiovascular disease which together now account for two-thirds of deaths in the affluent societies of the industrialized world. Part of the explanation for this change is that people are now much more likely to live into old age and become susceptible to degenerative diseases, especially if, as with some cancers, they have a genetic origin. However, some of the explanation, particularly with other types of cancers, lies in environmental factors – the increased pollution, in particular from the highly toxic artificial chemicals produced in the second half of the 20^th century.

Another factor, especially in the rise of cardiovascular diseases, has been the major change in diet over the last 200 years.
Many of the dietary changes have been beneficial in eliminating deficiency diseases. The average height of the population of medieval Europe was about 30 cm less than now.
However, many of the dietary changes have been harmful, in particular a reduction in fibre intake, a rise in sugar consumption, much higher levels of fat intake and a higher proportion of processed foods.
The reduction in the fibre content of food in the industrialized world has been associated with the rise of many complaints such as constipation, and intestinal disease together with colon and bowel cancer.
The rise in sugar consumption has had an even more deleterious effect on health. Until the rise of the great slave-worked sugar plantations of Brazil and the West Indies in the 17^th century the use of sugar was almost unknown.
Foods were sweetened using honey (or maple syrup in North America). By 1750 sugar intake in Europe and North America had risen to about 2 kilograms per person per year. It is now over 30 times that rate.
The most immediate effect was a rapid rise in dental caries. The rise in sugar consumption is also directly linked to the increase in the number of people suffering from diabetes.
Diabetes rates have risen sharply since the early 20^th century where it now affects 3% of the population of Britain and 7% in the United States where sugar consumption is even higher.
Fat intake has increased throughout human history. The first major step was the ‘secondary products revolution’ – the use of goat, sheep and cow milk to create dairy products.
The poor grazing and lack of fodder in the early agricultural systems meant that these animals had only a low output of milk and poor transportation meant that it was difficult to move products with a short life.
All these factors kept dairy consumption at relatively low levels. Technological changes in the late 19^th and early 20^th centuries – refrigeration, pasteurization, canning, and faster transportation – made products regularly available to the rapidly rising urban population.
The great consumption of meat also raised fat levels in the diet.
The technological changes were also central to the rise of a new phenomenon – the food industry, which concentrated on selling processed food rather than distributing fresh food.
Over the course of the 20^th century the consumption of processed food by the average American tripled and the consumption of fresh fruit and vegetables fell by over a third.
Processing food not only removes many of the nutrients and important trace minerals but also introduces additives such as antioxidants, emulsifiers, thickeners, flavour enhancers, dyes, artificial sweeteners and bleaching agents. Many of these are needed to disguise the poor quality of the initial ingredients.
The average person in Britain now consumes about 2 kilograms of these chemical additives every year.
All these changes in diet, linked to the much greater consumption of food, have had a major impact on human health in the affluent world.
The rate of obesity increased dramatically in the late 20^th century. In Britain one in five adults is now clinically obese – a rate double that of the 1970s.
In the United States the situation is far worse. About 60 million adults are obese – about a third of the population – with the rate having doubled since the 1970s.
In the early 1960s only 4% of American children were seriously overweight – in the next 40 years that rate quadrupled.
Obesity, excess food consumption and a diet high in fat significantly increases death rates, especially from cardiovascular diseases.
Heart disease was almost unknown a century ago except among the rich who could not afford a diet high in fat and sugar and ate too much food.
Even in 1930 coronary heart disease was responsible for only 1% of British deaths. By the mid-1990s this had increased to just over 30% and it is continuing to rise.
Part of the rise in heart disease can be attributed to the rise in smoking which increases the risk of contracting cancer by about a third and also increases the risk of heart disease, bronchitis and other lung diseases. In the 20^th century tobacco products probably killed 100 million people.
Cancer is now the second most common form of death in the industrialized world – 1 in 3 Americans contracts cancer (compared with 1 in 27 in 1900) and 1 in 4 dies of the disease.
Half of all the world’s cancers now occur in developing countries and here treatment is poor – about 80% of patients will die of the disease compared with 50% in the industrialized world.
Huge amounts of money have been spent over the last 50 years in an attempt to find cures and treatments for different types of cancers but overall the results have been disappointing except in the cases of some rare types of the disease. Most of the effort has gone into high-technology medical research and very little has been done to reduce the environmental factors in cancer apart from anti-smoking campaigns, which have had limited, though increasing, success in some countries.

Chapter 11: The Weight of Numbers

A Green History of the World Part 10

Chapter 10: Disease and Death (Cont)

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