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Estimating CVD risk and treatment benefit

Non-
smoker
Smoker
4 5 6 7 8 4 5 6 7 8
Blood pressure 180/105 AGE 70
160/95
140/85
120/75
180/105 AGE 60
160/95
140/85
120/75
180/105 AGE 50
160/95
140/85
120/75
180/105 AGE 40
160/95
140/85
120/75
4 5 6 7 8 4 5 6 7 8
Ratio of Total Cholesterol: HDL
Risk level Benefit:* CVD events prevented per 100 treated over 5 years
5 year CVD risk (non-fatal and fatal) Mid-range value (range) One intervention Estimated ARR 25% Two interventions Estimated ARR 45% Three interventions Estimated ARR 55%
Very high > 30% > 8 > 14 > 17
Very high 27.5% (25-30%) 7 12 15
Very high 22.5% (20-25%) 6 10 12
High 17.5% (15-20%) 4 8 10
Moderate 12.5% (10-15%) 3 6 7
Mild 7.5% (5-10%) 2 3 4
Mild 2.75% (2.5-5%) 0.7 1.2 1.5
Mild < 2.5% < 0.6 < 1.1 < 1.4
Risk level Benefit:* NNT to prevent one event over 5 years
5 year CVD risk (non-fatal and fatal) Mid-range value (range) One intervention 1/ARR Two interventions 1/ARR Three interventions 1/ARR
Very high > 30% < 13 < 7 < 6
Very high 27.5% (25-30%) 15 8 7
Very high 22.5% (20-25%) 18 10 8
High 17.5% (15-20%) 23 13 10
Moderate 12.5% (10-15%) 32 18 15
Mild 7.5% (5-10%) 53 30 24
Mild 2.75% (2.5-5%) 145 81 66
Mild < 2.5% > 160 > 89 > 73
ARR, absolute risk reduction

Notes

*Assumptions: A conservative estimate that each intervention: aspirin, blood pressure treatment (lowering systolic BP by 10 mm Hg) or lipid modification (lowering LDLC by 20%) reduces cardiovascular risk by about 25% over 5 years. The relative risk of a CVD event over 5 years after one intervention compared to no treatment is 0.75, after two is 0.75 x 0.75, and after three is 0.75 x 0.75 x 0.75 (i.e. the risk is multiplicative).

(1) People with a strong history of CVD (first degree male relatives with CVD before 55 years, female relatives before 65 years) or obesity (body mass index above 30 kg/m2) are likely to be at greater risk than the tables indicate. The magnitude of the independent predictive value of these risk factors remains unclear — their presence should influence treatment decisions for patients at borderline treatment levels. (2) If total cholesterol or total cholesterol : HDL ratio is greater than 8 then the risk is at least 15%. (3) Nearly all people aged 75 years or over also have an absolute cardiovascular risk over 15%.

Charts reproduced with permission from The National Heart Foundation of New Zealand. Also available on http://www.nzgg.org.nz/guidelines/0035/CVD_Risk_Full.pdf