Disability-Adjusted Life Years (DALYs) provide a comprehensive measure of disease burden by combining mortality and disability. The Global Burden of Disease (GBD) Study 2024 provides the most current estimates for neurodegenerative conditions. This page details the methodology used to calculate and validate DALY estimates for neurodegenerative diseases.
DALY = YLL + YLD
Where:
| Parameter | Description | Data Sources |
|---|---|---|
| Life expectancy | Standard life table (GBD 2024) | WHO Life Tables |
| Disability weights | Condition-specific (0 = perfect health, 1 = death) | GBD 2024 Disability Weights Survey |
| Prevalence | Number of existing cases | GBD 2024, national registries |
| Duration | Average disease duration | GBD 2024, clinical studies |
| Condition | Disability Weight | 95% CI | Severity Description |
|---|---|---|---|
| Alzheimer's/Dementia (mild) | 0.30 | 0.20-0.42 | Memory problems, difficulty with complex tasks |
| Alzheimer's/Dementia (moderate) | 0.55 | 0.38-0.72 | Memory deficits, needs help with daily activities |
| Alzheimer's/Dementia (severe) | 0.80 | 0.60-0.94 | Complete dependence, unaware of surroundings |
| Parkinson's (mild) | 0.15 | 0.10-0.22 | Some tremor, mild motor impairment |
| Parkinson's (moderate) | 0.40 | 0.27-0.54 | Significant motor impairment, some disability |
| Parkinson's (severe) | 0.65 | 0.46-0.82 | Severe disability, mobility aid required |
| ALS (mild) | 0.35 | 0.23-0.48 | Mild weakness, some functional limitations |
| ALS (moderate) | 0.60 | 0.42-0.77 | Significant weakness, needs assistance |
| ALS (severe) | 0.85 | 0.68-0.96 | Complete paralysis, ventilator-dependent |
Source: GBD 2024 Disability Weights
YLL = Σ (Deaths at age a) × (Life expectancy at age a)
| Disease | Typical Age at Death | Average YLL | Primary Death Driver |
|---|---|---|---|
| Alzheimer's | 80-85 years | 5-8 years | Complications (aspiration, infection) |
| Parkinson's | 75-80 years | 8-12 years | Respiratory failure, falls |
| ALS | 55-65 years | 15-25 years | Respiratory failure |
| FTD | 60-70 years | 10-15 years | Complications |
| Huntington's | 50-60 years | 20-30 years | Complications |
YLD = Σ (Prevalence at severity s) × (Disability weight at s) × (Duration)
| Data Source | Coverage | Limitations |
|---|---|---|
| National registries | High-income countries | Incomplete capture |
| Population surveys | Variable | Underdiagnosis bias |
| Health system data | Variable | Selection bias |
| Modeling (GBD) | Global | Uncertainty in estimates |
For diseases with multiple severity levels (AD, PD), GBD uses:
| Condition | DALYs (millions) | YLL | YLD | Change since 2019 |
|---|---|---|---|---|
| Alzheimer's & Other Dementia | 33.5 | 20.5 | 13.0 | +12% |
| Parkinson's Disease | 6.8 | 3.2 | 3.6 | +8% |
| Motor Neuron Disease | 2.4 | 2.1 | 0.3 | +3% |
| Other Dementias (FTD, LBD, VD) | 4.2 | 2.5 | 1.7 | +10% |
| Huntington's Disease | 0.6 | 0.35 | 0.25 | Stable |
GBD provides 95% uncertainty intervals (UI) for all estimates: