Epidemiological Interpretation: Higher Incidence in Females with Equal Prevalence
When females have a higher incidence rate but prevalence is equal to males, the disease duration must be shorter in females (Option B is correct). This fundamental epidemiological relationship is governed by the equation: Prevalence = Incidence × Duration 1.
Core Epidemiological Principle
The relationship between these measures requires mathematical equilibrium 2:
- If incidence is higher in females (more new cases per unit time)
- But prevalence is equal (same total number of existing cases at any given time)
- Then duration must be shorter in females to maintain this balance 1
This means females are either:
- Recovering faster from the condition
- Dying more quickly from the condition
- Or experiencing some combination of both outcomes
Why the Other Options Are Incorrect
Option A (Females harbor disease longer) is backwards - if females harbored disease longer with higher incidence, their prevalence would necessarily be higher than males, not equal 1, 2.
Option C (Higher case fatality in females) would be contradictory - higher case fatality in females would shorten disease duration in females, which is actually consistent with the scenario, but the question asks about males having shorter duration. Additionally, in most conditions where this pattern exists, males actually have higher case fatality rates 3, 4.
Option D (Higher mortality rate in females) is inconsistent with most epidemiological patterns where males demonstrate higher mortality across multiple disease states 1, 3.
Real-World Clinical Examples
This epidemiological pattern appears in several conditions:
COVID-19: Females had higher overall incidence rates in Canada (particularly among healthcare workers), but males had significantly higher case fatality rates and ICU admissions, resulting in shorter disease duration in males who either recovered or died more quickly 4.
Acute myocardial infarction: Historical data showed women had higher incidence in certain age groups but men had higher mortality, leading to shorter disease duration in males 5.
Aortic dissection: Males present more frequently and earlier, but females who develop the condition have worse outcomes with higher in-hospital mortality 6.
Common Pitfall to Avoid
Do not confuse incidence (new cases) with prevalence (existing cases). The key insight is that prevalence represents a "steady state" that depends on both how many people develop the disease (incidence) and how long they have it (duration). Higher input (incidence) with equal storage (prevalence) mathematically requires faster output (shorter duration) 1, 2.
The correct answer is B: the disease duration is less in males.