Colorectal Cancer - Descriptive epidemiology

Different populations worldwide experience different levels of colorectal cancer, and these levels change with time. Populations living in one community whose lifestyles differ from those of others in the same community also experience different levels of colorectal cancer. Groups of migrants quickly lose the risk associated with their original home community and acquire the patterns of the new community, often starting within one generation of arrival.

Colorectal Cancer - Survival and deprivation

The relation between poverty and ill health has been researched for more than 100 years. In Scotland, since the 1851 census, all cause occupational mortality has been routinely reported, and since 1911, inequalities in health, as shown by mortality, have been examined in decennial reports classified by social class (based on occupation) and by occupational group alone.

No single, generally agreed definition of deprivation exists. Deprivation is a concept that overlaps but is not synonymous with poverty. Absolute poverty can be defined as the absence of the minimum resources for physical survival, whereas relative poverty relates to the standards of living in a particular society. Deprivation includes material, social, and multiple deprivation. In Scotland the Carstairs and Morris index of deprivation was derived from 1981 census data with the postcode sector as the basic geographical unit (covering a population of about 5000). This index describes a deprivation category on a scale of 1 (least deprived) to 7 (most deprived) for each household address in Scotland.

The incidence of colorectal cancer is higher in men than women among each of the seven deprivation categories in Scotland, although incidence varies little with deprivation category. Survival, however, clearly improves with decreasing deprivation. At each milestone, there is a notable gradient in survival, with the most affluent doing best and the least affluent doing worst. The reasons that such variations exist are unclear and highlight an important priority for research.

Colorectal Cancer

Estimated incidence of colorectal cancer
in United Kingdom, by age and sex, 1995

In countries with a westernised lifestyle about half of all deaths are caused by circulatory disease and a quarter by cancer. Cancer is an important problem in both public health and political terms worldwide, irrespective of a country’s development. The most recent estimates of the global cancer burden suggest that there were 8.1 million new cases, excluding non-melanoma skin cancer, worldwide in 1990. About 10 million new cases are now diagnosed each year. 

Colorectal cancer is the fourth commonest form of cancer occurring worldwide, with an estimated 783 000 new cases diagnosed in 1990, the most recent year for which international estimates are available. It affects men and women almost equally, with about 401 000 new cases in men annually and 381 000 in women. The number of new cases of colorectal cancer worldwide has been increasing rapidly since 1975 (when it was 500 000).