In medicine, prevention is an activity which reduces the burden of mortality or morbidity from disease. Preventive medicine takes the form of primary, secondary and tertiary prevention.
Primary prevention is aimed at preventing the clinical development of a disease. For example, health promotion activities are primary preventive measures. Ultimately, the goal for Alzheimer's disease is to employ lifestyle interventions and disease modifying drugs to prevent the clinical onset of cognitive impairment and dementia.
Secondary prevention seeks to prevent the progression of disease in its earliest stages. For Alzheimer's disease, we seek drugs to prevent or halt the progression in its earliest stages when individuals are still functional.
Tertiary prevention decreases the harmful consequences of an established disease by restoring function and reducing disease-related complications. For Alzheimer's disease, tertiary prevention is primarily achieved through care management to prevent the complications of the disease, such as functional impairment and, in the end stages, pneumonia and other infections.