A small town has a population of 250,000. In a five year period there was 1,000 cases of lung cancer diagnosed in that town. The neighbouring town also has a population of 250,000 but only 400 people were diagnosed with lung cancer during the five year period. What is the annual incidence per million of lung cancer in the population of both of these towns?
A. 2800
B. 1400
C. 700
D. 560
E. 1800
Incidence in epidemiology is a measure of the probability of occurrence of a given medical condition in a population within a specified period of time. As the question specifically asked for annual incidence per million, the calculation should be as below: 1000 + 400 = 1400 250 000 + 250 000 = 500 000 There are 1400 people diagnosed with lung cancer in a population of 500 000 in 5 years. 1 000 000 / 500 000 = 2 Incidence per million in 5 years = 2 x 1400 = 2800 Incidence per million in 1 year = 2800 / 5 = 560