Table 1.
Comparison of the original Late-Life and Brief Dementia Risk Indices*
| Original Late-Life Dementia Risk Index15 | Brief Dementia Risk Index** | ||||
|---|---|---|---|---|---|
| Characteristic | Coeff. | Points | Characteristic | Coeff. | Points |
| Age 75–79 years | 0.66 | 1 | Age 75–79 years | 0.84 | 1 |
| Age 80–100 years | 1.19 | 2 | Age 80–100 years | 1.62 | 2 |
| Low 3MS | 1.04 | 2 | Delayed recall < 2 of 3 words | 1.00 | 2 |
| Low DSST | 0.90 | 2 | Incorrectly copying intersecting pentagons | 0.68 | 1 |
| ≥ 1APOE ε4 allele | 0.79 | 1 | Incorrectly taking or folding paper | 0.65 | 1 |
| MRI white matter disease | 0.61 | 1 | Inability to name 10 four-legged animals in 30 s | 0.40 | 1 |
| MRI enlarged ventricles | 0.38 | 1 | Self-reported `trouble keeping mind on things' ≥ 3 d/wk | 0.64 | 1 |
| Internal carotid artery thickness ≥ 2.2 mm | 0.57 | 1 | Stroke | 0.56 | 1 |
| Time to put on and button shirt > 45 s | 0.50 | 1 | Peripheral artery disease | 0.66 | 1 |
| Coronary artery bypass surgery | 0.54 | 1 | Coronary artery bypass surgery | 0.56 | 1 |
| BMK < 18.5 | 1.22 | 2 | BMK < 18.5 | 0.84 | 1 |
| Lack of current alcohol consumption | 0.42 | 1 | Lack of current alcohol consumption | 0.46 | 1 |
| Constant | −4.07 | −4.03 | Constant | −3.52 | −3.53 |
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| c statistic | 0.82 | 0.81 | c statistic | 0.77 | 0.77 |
An individual's probability of dementia is calculated as 1 / [1 + e−(α + Σβx)] where α=constant, β=coefficient, and x=variable value. This can be calculated directly from the model coefficients in Table 1 or, if using the point system, β=0.52 per point for the original index and β=0.60 per point for the brief index. For example, using the brief index, the predicted probability of developing dementia within 6 years for someone who was 75 years old; recalled 1 of 3 words presented; was unable to copy the pentagon figure correctly; did not fold the paper; named 5 four-legged animals in 30 seconds; reported trouble keeping their mind on what they were doing 5 days/week; did not have a history of stroke, peripheral artery disease, or bypass surgery; had normal BMI; and did not currently drink alcohol would be 1 / [1 + e−(−3.52 + 0.84 + 1.00 + 0.68 + 0.40 + 0.64 + 0.46)] = 76% using the model coefficients and 1 / [1 + e−(−3.53 + 0.60*8)]= 78% using the point system.
The accuracy of the Brief Dementia Risk Index was improved slightly (c statistic=0.78) using age as a continuous variable and the following alternative model coefficients: β(age)=0.13 per year, β(delayed recall)=1.00, β(pentagons)=0.67, β(paper)=0.65, β(animals)=0.40, β(mind on things)=0.61, β(stroke)=0.50, β(peripheral artery disease)=0.67, β(bypass)=0.59, β(low BMI)=0.84, β(no alcohol)=0.46, constant=−12.52.