Question

What happens to the prevalence of a disease if the duration of the illness increases while incidence remains constant?

• A. Decreases
• B. Remains unchanged
• C. Increases
• D. Becomes zero

Hint:

Prevalence $\propto$ Duration. Longer disease duration $\Rightarrow$ More existing cases.

Answer 1

The Correct Option is C

Concept: Prevalence refers to the total number of existing cases of a disease in a population at a given time, while incidence refers to the number of new cases occurring over a period. They are related by the formula: \[ \text{Prevalence} = \text{Incidence} \times \text{Duration of disease} \]
Step 1: Understand the relationship.
Prevalence depends directly on both incidence and duration.
Step 2: Analyze the given condition.
If incidence remains constant and duration increases, the product (incidence $\times$ duration) increases.
Step 3: Interpret the result.
An increase in duration means patients live longer with the disease, leading to accumulation of cases.
Step 4: Conclude the answer.
Thus, prevalence increases.