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.

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. The power to detect associations with all-cause mortality approximates to 100% in each of these cells

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.