Your race and age

The incidence of prostate cancer varies enormously around the world. It is unusual in the Far East and in rural areas of Africa. Some clues as to the causes of prostate cancer have been provided by studies of migrating populations.

Prostate cancer age-specific incidence rates

The rate of prostate cancer in different populations

One such study involved migrants from Japan and China who had settled in the United States and Hawaii in the mid-19th century.

These communities were relatively insular and there was little inter-marriage. Over the generations that succeeded the first wave of immigration there have been significant changes in the incidence of prostate cancer. The first generation of migrants were called the Issei, and the second generation the Nissei.

For every 10 Caucasian Americans dying from prostate cancer, there was only 1 Japanese death in the initial migrant generation: a ratio of 10:1. This ratio changed to 5:1 for the Issei and to 1.5:1 for the Nissei. Given that there was such little inter-marriage, one looks for other factors that may be causing the increased incidence of the development of prostate cancer. Where these migrants are concerned, the only thing that has really changed is their environment.

In the case of African-Americans the disease is even more significant than in white populations. As the following table clearly shows, the risk of African-Americans developing prostate cancer is so much greater that it is similar to that of white Americans of much greater age. We have no idea why this should be, although it is possible that there are complex biochemical differences at the level of DNA between Afro-Caribbeans and Caucasians involving what are termed ‘tri-nucleotide repeats’ on the Y chromosome.

Prostate cancer is an illness of older men. That is, the incidence of prostate cancer increases almost exponentially as men age, and this can be seen in the table above. This is yet further evidence that prostate cancer is caused by environmental factors, because the environmental risk factors accumulate as you grow older. The longer you live, the more environmental risk factors you will have been exposed to.