Epidemiology: An introduction by The Open University

Author:The Open University [University, The Open]
Language: eng
Format: epub
Published: 0101-01-01T00:00:00+00:00

Figure 9 Estimated number of adults and children newly infected with HIV during 2007 (Source: UNAIDS Report Epidemic 2007)

Within countries, regional variations in the occurrence of diseases are not uncommon. In addition, differences in disease patterns between urban and rural communities are frequently observed. Even within one health district, mortality rates due to particular diseases may vary from one electoral ward to another.

Studies of immigrant populations focus on separate groups within geographical areas. One such population was that which migrated from Japan to the USA between 1890 and 1924. It was found that heart disease in Japan was only one-quarter the rate of that in the USA, whereas stroke and cerebral haemorrhage were two or three times more common (Marmot et al., 1975). Stomach cancer was five times more common in Japan, but cancer of the breast and prostate were very uncommon; cancer of the cervix was twice as common in Japan as in the USA. As the Japanese population settled in the USA, some of their disease patterns changed, and conditions such as stroke, cerebral haemorrhage and cancer of the cervix approached the rates of the community to which they had migrated. This suggests that environmental factors played a considerable part in the causation of these particular diseases. Cancer of the stomach also declined, but not to a very great extent (Hirayama et al., 1980). Cancer of the breast, however, did not alter significantly when the population had settled in the USA. Caution must be exercised when making international comparisons of illhealth. In developing countries, access to biomedical treatment and the availability of facilities for investigation can be restricted. This means that there may be problems with the accuracy and completeness of diagnosis. The age structure of the population in developing countries, with a greater proportion of young people than in the industrialised world, also makes comparisons of disease frequency difficult.

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