Non-communicable Diseases and Chronic Disease Prevention
Core concepts
Non-communicable diseases share modifiable risk factors: tobacco, unhealthy diet, physical inactivity, harmful alcohol use, and air pollution. Know primordial, primary, secondary, and tertiary prevention, and the population-wide versus high-risk strategy. Screening requires a suitable disease, accepted test, effective treatment, and adequate follow-up. Cardiovascular risk assessment combines age, sex, smoking, blood pressure, diabetes, and lipids. Understand WHO best buys, MPOWER tobacco control, salt reduction, obesity prevention, cancer screening, and multimorbidity. Rose's paradox explains why small population shifts can produce larger total benefit than intensive high-risk care.
Traps
Screening is not automatically beneficial; lead-time bias, length-time bias, and overdiagnosis can exaggerate survival. Primary prevention precedes disease; secondary prevention detects early disease. NCDs are not diseases of affluence only; they disproportionately affect poor populations. A statistically significant risk factor may have a small population impact. Do not confuse a relative risk reduction with an absolute risk reduction.
Worked example
In a trial, the event rate falls from 20% to 14%. Absolute risk reduction = 6 percentage points; number needed to treat = 1/0.06 = 16.7, about 17 patients treated to prevent one event. Relative risk reduction = 6/20 = 30%, a more impressive-sounding figure that should not replace the absolute effect.
Rule of thumb
Combine population-wide measures with targeted high-risk management; always report absolute risk.