Understand and apply the formula for calculating Number Needed to Harm (NNH), which indicates how many patients need to be exposed to a risk factor or treatment for one additional person to be harmed.

Formula:

Explanation:

• = Attributable Risk (difference in risk of adverse outcomes between exposed and unexposed groups)
• NNH quantifies the harm potential of an exposure or treatment.
• Higher NNH → safer exposure (fewer people harmed)
• Lower NNH → more harmful exposure

Example:

Given:
(5% additional risk in the exposed group)

✅ Answer: NNH = 20
→ For every 20 people exposed, 1 additional person is harmed due to the exposure.

Activity: