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Table 3 Power to detect given effect sizes (HRs) for associations between exposures with a prevalence of 10% and 20%, for the outcomes of dementia and stroke.

From: The protocols for the 10/66 dementia research group population-based research programme

Minimum Hazard Ratio to be detected Power for detecting association with 10% exposure prevalence Power for detecting an association with 20% exposure prevalence
Outcome1,2 Dementia Stroke Dementia Stroke
2.5 100% 99.8% 100% 100%
2.0 96.4% 90.9% 99.8% 98.8%
1.8 86.0% 75.8% 97.5% 92.8%
1.5 48.8% 39.3% 71.0% 59.5%
  1. 1. The power to detect associations with all-cause mortality approximates to 100% in each of these cells
  2. 2. As approximately 70% of dementia cases are categorised as AD, the power of detecting given associations with this outcome is very similar to that for stroke.