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Science Olympiad» Disease Detectives Event » National Event Exercises
Skin Cancer Module: Practice Exercises

Skin Cancer: Module 5
Crude Incidence Rates Exercise

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Question 1: What does "age-specific" mean in this chart? What is in the numerator and in the denominator? How are "age-adjusted" incidence rates different from "age-specific" incidence rates? What might be the advantage of looking at age-specific rates on lung and bronchus cancer?

Answer: In this chart, age-specific incidence rates reflect the number of cases of lung and bronchus cancer in a particular age group. To find age-specific incidence rates of lung and bronchus cancer:

  • The numerator is the number of cases in the age group.
  • The denominator is the number of people in that age group included in the study.

Age-adjusted incidence rates are not limited to a particular age group. Instead they let us compare overall rates between populations with different age distributions.

Understanding age-specific rates helps us judge the risk and public health impact of this disease on a population. It helps us target resources for prevention, screening, and treatment.

 

Question 2: What happens to the incidence of lung and bronchus cancer as people get older?

Answer: Rates of lung and bronchus cancer go up rapidly from the mid-30s to the mid-to-late 70s. Rates go down slightly in people over 80 years. These statements are true for all sub-populations.

 

Question 3: What can you say about lung and bronchus cancer incidence rates among men compared to women? Among black men compared to white men? Among black women compared to white women? What factors might explain these differences?

Answer: Answers should include—

  • The rate of lung and bronchus cancer is highest in black males, followed by white males.
  • Black and white females have similar rates of this cancer. But their cancer rates are lower than men of either race.

Reasons for these differences may include—

  • different rates and types of tobacco use (These may be caused by social factors, culture, advertising, type/quality/availability of tobacco products, etc.)
  • different rates of environmental exposure to cigarette smoke and other carcinogens
  • access to counseling and/or social support to quit smoking
  • access to primary health care, etc.

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This page last reviewed August 27, 2004

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