The world health report

Chapter 4


Global patterns of risks to health

Three major groupings of countries can be defined by geography, state of economic and demographic development, and mortality patterns. As can be seen from Figure 4.8, these regions differ substantially in their disease patterns. This phenomenon reflects what is known as the "epidemiological transition" -- as life expectancy increases, the major causes of death and disability in general shift from communicable, maternal and perinatal causes to chronic, noncommunicable ones. At present, about one-tenth of disease burden is caused by injury in all three regions.

The risk factors analysed in this report are responsible for a substantial proportion of the leading causes of death and disability in these regions, as shown by the mapping of risk factors to diseases and the range of population attributable fractions in Annex Tables 14, 15, and 16. Their ranking globally, and their distribution by broad region, is shown in Figure 4.9.

Additionally, the ranking of risks within major world regions, by level of development and affected disease or injury outcomes, is shown in Figure 4.10.

Perhaps the most striking finding is the extraordinary concentration of risks in the high mortality developing countries. Among these countries with just over two-fifths of the world's population, not only are the rates of disease and injury particularly high, but the contribution made by relatively few risk factors is particularly great. About one-sixth of the entire disease burden in these countries is attributed to underweight, with a substantial additional proportion attributable to micronutrient deficiencies. The burden resulting from these risks alone approaches that of the entire disease and injury burden in industrialized countries. Just over one-tenth of all disease burden in high mortality developing countries is attributable to unsafe sex, with unsafe water accounting for about 4--5% of the burden. In all the high mortality developing regions, underweight, unsafe water, sanitation and hygiene, and indoor smoke from solid fuels feature in the leading six of these selected risks. In addition, unsafe sex is the leading risk in AFR-E and second leading risk in AFR-D. Virtually all of the substantial burden attributable to these risks is borne by developing countries.

For industrialized countries, with just over one-fifth of the world's population , tobacco is the leading risk factor, accounting for about 12% of all disease and injury burden. For both sexes, alcohol and blood pressure account for 9--10% of DALYs, and cholesterol and body mass for 6--7% of DALYs. Alcohol, blood pressure, overweight, cholesterol and tobacco are the leading five risks for each subregion in the industrialized group, varying only in their rank order.

An intermediate picture is seen for the low mortality, developing regions, with alcohol, tobacco and high blood pressure each accounting for about 4--6% of disease burden. Alcohol is the leading cause, alone accounting for about 6.2%. Indoor smoke from solid fuels and unsafe water and hygiene also feature in the ten leading risk factors for these areas. This double burden is seen most clearly for body weight -- underweight and overweight are each responsible for about 3% of disease burden. Overall, however, the pattern of leading risks already most closely resembles that in industrialized countries.

These results provide a cross-sectional indication of an epidemiological transition for risk factors. The epidemiological transition that accompanies economic development has traditionally been understood in terms of outcomes, that is, patterns of disease and injury. This report shows some key drivers of this transition -- risk factors that shape the development of disease and injury patterns.

The gradient of burden attributable to leading risks and diseases has a bearing on the appropriate degree of focus of public heath initiatives. In all three broad regions the leading disease or injury outcomes account for about three or four times more burden than the tenth ranked outcomes. However, the leading risk factor accounts for about 16 times more burden than the tenth ranked risk factor from this selected group in the industrialized countries. The ratio is less extreme but still considerable for high mortality developing countries, where the leading risk (underweight) accounts for about eight times more burden than the tenth ranked risk (cholesterol). For the low mortality developing countries, the ratio is even less marked, being about four-fold. Clearly, highly focused public health initiatives could be comparatively effective in the richest and the poorest countries, whereas in middle income countries the public health agenda of tackling major risks may have to be taken up on wider fronts.

Looking at the selected risk factors by proportion of attributable burden might obscure the vast absolute amount of burden caused by risk factors in the large developing regions. Because such a large proportion of the world's population live in developing countries, and background disease rates and risk factor levels are often high, the absolute number of DALYs attributable to each risk factor is greater than that in developed countries. Even for risks traditionally thought to be "Western", such as elevated body mass or cholesterol, more burden now occurs in developing than developed countries. The shift appears to have occurred for tobacco in the 1990s -- about a decade ago more tobacco deaths occurred in the developed than the developing world. This report suggests the predominance of tobacco burden has now begun to shift to the developing world.

The distribution of attributable deaths and DALYs by age and sex is shown in Tables 4.9 and 4.10 and in Annex Table 8. Underweight and micronutrient deficiency-related burden clearly affect children almost exclusively, as do unsafe water and climate change. The burden in terms of DALYs due to other diet-related risks and occupational risks (except injury) is almost equally distributed among adults above and below the age of 60 years. The burden caused by addictive substances, unsafe sex, lack of contraception, risk factors for injury, unsafe health care injections and childhood sexual abuse mostly or almost all occurs in middle-aged adults. Diet-related and environmental risks and unsafe sex are about equally distributed among the sexes. However, about four-fifths of burden as a result of addictive substances, and about 60--90% of burden from separate occupational risks, occurs among men. Women suffer the majority of burden from childhood sexual abuse and all of the burden caused by a lack of contraception. Women are also affected more by those nutritional deficiencies that affect maternal conditions (iron and vitamin A deficiency).

One further major finding is the key role of nutrition in health worldwide. About one-fifth of the global disease burden can be attributed to the joint effects of protein--energy or micronutrient deficiency. In addition, almost as much burden again can be attributed to risk factors that have substantial dietary determinants -- high blood pressure, cholesterol, overweight, and low fruit and vegetable intake. These patterns are not uniform within regions, however, and in some countries the transition has been much healthier than in others.The many and varied factors that determine national nutritional patterns are clearly a key determinant in achieving a healthier transition (see Box 4.10).

Box 4.10 Healthy risk factor transition

The "nutritional transition" encompasses changes in a range of risk factors and diseases. As a country develops and more people buy processed food rather than growing and buying raw ingredients, an increasing proportion of calories tends to be drawn from sugars added to manufactured food and from relatively cheap oils. Alongside the change in diet, changes in food production and the technology of work and leisure lead to decreases in physical exercise. The consequent epidemic of diet-related noncommunicable diseases (obesity, diabetes, hypertension and cardiovascular disease) coexists with residual undernutrition, and is projected to increase rapidly. For example, in India and China, a shift in diet towards higher fat and lower carbohydrate is resulting in rapid increases in overweight -- among all adults in China and mainly among urban residents and high income rural residents in India.

Countries which have completed the transition to overnutrition are experiencing a continual increase in levels of obesity, as high fat, high sugar and low exercise lifestyles permeate society. However, this transition may not be inevitable, and a key challenge for policy-makers is to generate a "healthier transition".

The Republic of Korea is an example of a country that has experienced rapid economic growth and the introduction of Western culture since the 1970s. There were large increases in the consumption of animal food products, and a fall in total cereal intake. Despite this, national efforts to retain elements of the traditional diet -- very high in carbohydrates and vegetables -- seem to have maintained low fat consumption and a low prevalence of obesity.

Civil society and government initiatives to retain the traditional diet and cooking methods in the Republic of Korea have been strong: mass media campaigns, such as television programmes, promote local foods, emphasizing their higher quality and the need to support local farmers. A unique training programme is offered by the Rural Development Administration. Since the 1980s, the Rural Living Science Institute has trained thousands of extension workers to provide monthly demonstrations of cooking methods for traditional Korean foods such as rice, kimchi (pickled and fermented Chinese cabbage) and fermented soybean food. These sessions are open to the general public in most districts in the country, and the programme appears to reach a large audience.

Sources: (118,121)