Epidemiology of Alzheimer’s Disease
Carla Falkenstein, MS
Course Content • Description of the disease process. • Possible etiology based on population studies. • Global prevalence.
What is Alzheimer’s Disease? • Neurodegenerative disease. • Most common form of dementia. • Causes impaired cognitive functioning. • No known cure.
Diagnosis of AD Because it is a progressive disease with one of the earliest symptoms being memory loss, diagnosis is difficult.
Common Symptoms
• Forgetting names and objects. • Not recognizing family & friends. • Forgetting one’s own phone number or address. • Difficulty finding a familiar place. • Noticeable language & intellectual decline.
Common Symptoms (cont’d)
• Forgetting to eat or maintain one’s hygiene. • Poor judgment, inability to follow simple instructions. • Progressive sense of distrust. • Unusual agitation and irritability.
Age is a Primary Risk Factor
50 45 40 35 30 25 20 15 10 5 0 65 -74 75-84 85+
Prevalence of AD(%)
Ages Prevalence 65-74 = 3% 75-84 = 18.7% 85+ = 47%
Stages of AD
SEVERE 1-3 Years
MODERATE 2-10 Years
MILD 2-4 Years
Disease Process
Disease Process (cont’d)
• 1st destroys neurons in parts of the brain that control memory. • Later attacks cerebral cortex areas responsible for language and reasoning. • Eventually nearly the entire brain is atrophied.
Cause of Nerve Cell Death Amyloid Plaques? Neurofibrillary Tangles?
Amyloid Plaques
•Insoluble deposits of betaamyloid •Plaques found in the spaces between the brain’s nerve cells •Plaques may be a cause or a by-product of AD
Neurofibrillary Tangles
•Twisted threads of a protein called tau.
•Tau is a protein found inside nerve cells.
•In AD, Tau changes so that it becomes 2 threads wound around each other.
Other Genetic Factors
APOE є4 allele of the APOE gene is a major risk factor for late-onset AD.
However, much work is being done to sort out all the potential genetic factors involved in AD.
AD and Other Disorders
AD has similarities with other neurodegenerative diseases: •Prion, Parkinson’s and Huntington’s diseases all cause dementia. •All involve deposits of abnormal proteins in the brain.
Early Diagnosis
The earlier a correct diagnosis can be made, the greater the gain in managing symptoms through pharmaceuticals.
•MRI •PET •SPECT
Causal vs. Associative Agents
•Advanced age •Female gender •Head Injury •Cerebrovascular disease •Low education levels •Rural Residence •Blood cholesterol •Low blood levels of folic acid •Inflammation
A Chain of Events Leads to Disability and Death
GENES
LIFESTYLE & ENVIRONMENT BRAIN DEVELOPMENT & RESERVE ALZHEIMER’S SEVERITY IN BRAIN
NEURODEGENERATION
OTHER DISEASES
AGE AT ONSET OF SYMPTOMS
SEVERITY OF SYMPTOMS
Global Prevalence of AD
United States •Most common cause of AD •Current cases: ~4 million •Prevalence doubles every 5 years beyond age 65 •Nearly 50% of those aged 85+ have AD
Global Prevalence of AD
•African Americans in Indianapolis are twice as likely as Africans in Ibadan, Nigeria to develop dementia & AD. •Higher rates of AD in Japanese men who emigrated to US compared with those who remained in Japan.
Global Prevalence of AD
Europe
There are currently an estimated 5.5 million people with dementia in Europe.
Global Prevalence of AD
Developing Countries Currently, ~18 million people in the world have dementia. 66% of people with dementia live in developing countries.
Current Research
•Continued search for causative agents and etiology. •Disease prevalence worldwide with close attention to cultural variations. •Animal and population studies that confirm causation and lead to preventive or curative measures.