Question

An investigator wanted to know whether chronic lymphocytic leukemia (CLL) had a genetic or environmental etiology. He knew that rates in country X were higher than those in the United States. He decided to study the rates in the country of origin, in migrants, and in U. S. whites. He observed the following:
Population Rate Country X 50/100,000
Migrants from Country X to U. S. 10/100,000
U. S. whites 10/100,000

What are the reasons for this relationship?

Answer 1

Answer:

The cause may be environmental

Explanation:

The ratios show that ratio of incidence of chronic lymphocytic leukemia (CLL) in the population of country X is five times higher than the ratio in U.S. whites. However, the ratio of CLL in migrants from Country X to the U. S. is exactly the same as the ratio in U.S. whites. This relationship indicates that, rather than being genetic, the cause of CLL is more likely to be environmental.