Questions: Chronic Disease Epidemiology and Risk Factor Surveillance

Question 1

A patient has hypertension (2× baseline cardiovascular risk) and is also a smoker (2× baseline cardiovascular risk). What is the best estimate of their combined cardiovascular risk?

• A. 2× baseline risk — the higher risk factor dominates
• B. 4× baseline risk — the risks add together
• C. 8–10× baseline risk — the risks multiply and compound each other
• D. 3× baseline risk — there is partial overlap between the two risk factors

Answer: (C)

Risk factors for cardiovascular disease interact multiplicatively, not additively. A person with both hypertension and smoking has roughly 8–10× the baseline risk, far exceeding the simple sum (4×). This is why composite risk calculators like the Framingham Risk Score are essential — individual risk factors severely underestimate a person's true absolute risk. Option B (additive) is the common misconception; the actual multiplicative compounding is what makes multi-factor risk assessment indispensable.

Question 2

Which statement best characterizes the current global distribution of non-communicable disease burden?

• A. NCDs are primarily diseases of wealthy nations; low-income countries still face mostly infectious disease
• B. NCDs are equally distributed across all income levels globally
• C. Low- and middle-income countries now bear the greatest NCD burden, often alongside significant infectious disease
• D. NCD burden is determined almost entirely by genetic factors, making geographic patterns less meaningful

Answer: (C)

Low- and middle-income countries now account for the majority of NCD deaths — this is one of the most important corrections to the 'diseases of affluence' misconception. As the epidemiologic transition unfolds globally, LMICs experience rising NCD burden before developing the health system infrastructure to manage chronic, longitudinal conditions. Many face a 'double burden': persisting infectious disease mortality plus accelerating NCDs, which fundamentally changes how global health resources should be allocated.

Question 3

Low- and middle-income countries now account for the majority of global NCD (non-communicable disease) deaths.

• T. True
• F. False

Answer: True

NCDs account for approximately 74% of global deaths, and the majority occur in LMICs — not in wealthy countries. The epidemiologic transition (declining infectious disease mortality as populations live longer) is occurring rapidly in LMICs, but without the decades of health system development that high-income countries had. Understanding this is essential to accurate NCD surveillance and global health policy.

Question 4

When epidemiologists label a risk factor 'modifiable,' they mean that individuals can realistically change their behavior to reduce that risk factor.

• T. True
• F. False

Answer: False

'Modifiable' in epidemiology means there is causal evidence that changing the exposure changes disease risk — it is a statement about causality, not behavioral feasibility. Tobacco use is modifiable because quitting reduces lung cancer risk; it does not imply that individual smokers can easily quit. This distinction matters enormously: it prevents individual-blame framings of prevention and points toward structural interventions (taxation, zoning, food environment policy) that shift population-level risk factor distributions more effectively than relying solely on personal behavior change.

Question 5

What does the 'epidemiologic transition' explain, and why does it create a 'double burden of disease' in low- and middle-income countries?

Model answer: The epidemiologic transition describes the shift from infectious diseases as the dominant cause of death to non-communicable diseases, as population health improves through sanitation, vaccines, and antibiotics and people live long enough to develop chronic conditions. In LMICs, this transition is happening rapidly but without the health system infrastructure to manage chronic disease — so these countries still face significant infectious disease mortality while NCD deaths accelerate simultaneously.

The double burden is critical for understanding health system design. A system optimized for acute infectious disease — vertical disease programs, curative care, episodic visits — is poorly matched to managing diabetes, hypertension, and cancer, which require sustained longitudinal care, medication adherence, and behavioral support. Policy makers in LMICs face competing demands on limited resources, and the epidemiologic transition concept explains why neither infectious nor chronic disease programs alone are adequate.