A public health team in Delhi conducted a cross-sectional survey in January 2024 to assess the burden of type 2 diabetes mellitus in a population of 50,000 adults aged 30–60 years. They identified 2,500 individuals with diabetes (both newly diagnosed and previously known cases). In the same population, during the 12-month period from January to December 2023, 300 new cases of diabetes were diagnosed. What is the prevalence of diabetes in this population, and which measure best reflects the disease burden at a single point in time?

Question

Accepted Answer

D. Prevalence = 5%; it measures the proportion of the population with the disease at a specific point in time. ## Calculation of Prevalence

**Prevalence** is calculated as:
$$	ext{Prevalence} = \frac{	ext{Total number of cases (old + new) at a point in time}}{	ext{Total population at that point in time}} 	imes 100$$

In this scenario:
- Total cases identified in January 2024 = 2,500
- Total population surveyed = 50,000
- Prevalence = (2,500 / 50,000) × 100 = **5%**

## Key Distinction: Incidence vs. Prevalence

| Measure | Definition | Time Frame | Use Case |
|---------|-----------|-----------|----------|
| **Prevalence** | Proportion of population with disease at a *point* in time | Cross-sectional snapshot | Disease burden, planning services |
| **Incidence** | Number of *new* cases occurring in a defined period | Longitudinal (e.g., 1 year) | Disease risk, causation, etiology |

**Key Point:** Prevalence answers "How many people have the disease right now?" Incidence answers "How many new cases occurred over a period?"

## Incidence Calculation (for context)

Incidence rate = (300 new cases in 2023) / (50,000 population) × 100 = **0.6%** or 600 per 100,000 per year.

**High-Yield:** Prevalence is a *proportion* (dimensionless, expressed as %); incidence is a *rate* (has time dimension, e.g., per 1,000 per year). Prevalence is useful for healthcare planning and resource allocation. Incidence is more useful for understanding disease etiology and evaluating prevention programs.

**Clinical Pearl:** In chronic diseases like diabetes, prevalence is typically much higher than incidence because patients remain in the "disease pool" for years. In acute diseases (e.g., influenza), incidence and prevalence may be closer.

**Mnemonic:** **P**revalence = **P**oint in time (snapshot); **I**ncidence = **I**nterval over time (new cases).

Answer

A. Incidence = 5%; it measures the number of new cases occurring over a defined period

Answer

B. Incidence = 0.6%; it measures the proportion of the population with the disease at a specific point in time

Answer

C. Prevalence = 0.6%; it measures the number of new cases occurring over a defined period

Explanation

Practice similar questions