Descriptive Epidemiology of Parkinson’s Disease and associated risk factors

ByRana Das, (Bsc. Hons. Medical biotech)

How we view the world…..• Pessimist: The glass is half

empty.

• Optimist: The glass is half full.

• Epidemiologist: As compared to what?

RIP..!!

Definition of Epidemiology*

Md. Ali affected with Parkinson’s

Pope John Paul II

Origins of Parkinson’s• Parkinson's disease was first formally described

in "An Essay on the Shaking Palsy," published in 1817 by a London physician named James Parkinson• It has probably existed for many thousands of

years• Symptoms and potential therapies mentioned in:• Ayurveda, the system of medicine practiced in India as

early as 5000 BC• First Chinese medical text, Nei Jing, which appeared

2500 years ago

Etiology• The cause of Parkinson’s disease is unknown. • Many researchers believe that several factors

combined are involved: free radicals, accelerated aging, environmental toxins, and genetic predisposition.

What Causes Parkinson's?• Why an individual develops Parkinson's

disease remains unclear. • The cause is probably a combination of

genetic and environmental factors, and may vary from person to person. • Although the cause of Parkinson's remains

unknown, scientists have identified factors that contribute to Parkinson's in some patients. • People over age 60 have a two-to-four percent risk

of developing Parkinson's disease, compared with the one-to-two percent risk in the general population.

Causes of Parkinson’s

On a cellular level• Studies have shown that the accumulation of a protein alpha

synuclein in the neurons lead to the formation of lewy bodies which inhibit the transmission of dopamine from one neuron to other.

• Over production of alpha synuclein is related to mutaion in the SYNCA gene.

Inhibition of Dopamine

PrevalenceHow many people have PD?

Estimated 1 million patients in US Second most common age-related neurodegenerative disorder Second in frequency only to Alzheimer’s disease World-wide estimates vary

15/100,000 in China 657/100,000 in Argentina

100 - 250/100,000 in North America and Europe Prevalence is predicted to triple over the next 50 years as average age of population increases.

Incidence Quantifies the number of individuals who are newly diagnosed with PD in a given time period Unaffected by factors affecting disease survival Accurate measurements of the incidence of PD are relatively difficult

Clinical manifestations of PD may be preceded by a long latent stage and have a slow clinical progression

IncidenceDifficult to know how many people are diagnosed each year: Symptoms may develop and progress slowly Diagnostic criteria may vary Patient populations vary with respect to doctor visits

Incidence

China: 1.5/100,000 Finland: 14.8/100,000 US: 20/100,000

Variations may be due to different diagnostic criteria and methods of case ascertainment in studies Lifetime risk of PD: 1 in 40

Age The incidence of PD increases with age

Symptoms of Parkinson’s disease may appear at any age

The median age of onset for idiopathic PD is 62.4 years

Onset before age 30 is rare, but up to 10% of cases of idiopathic PD begin by age 40

Age• Prevalence increases with age from age 50-90• Affects 0.3% of general US population• Affects 3% of those older than 65• Aging alone does not cause PD• May increase susceptibility to other factors or allow

them to be expressed

Gender

Slightly more common in men than in women

Estimated 12-15 men for every 10 women

Ethnicity

Present worldwide, in all populations No region found to be free of PD More common in white people in Europe and North America

(100-350/100,000)

Lower rates in China, Nigeria and Sardinia The disorder occurs in all races but is somewhat more prevalent among Caucasians

Ethnicity Generally less common among African-Americans and Asians

one-fifth to one-tenth as prevalent as in whites

In Africa less common among blacks than whites Door-to-door screening in Mississippi

PD prevalence was not significantly different in whites and blacks after adjusting for age differences (poor diagnostic

criteria) Higher prevalence in whites with stronger diagnostic

criteria

Ethnicity

Two other studies conducted PD incidence in African-Americans and in Asian-Americans was similar to rates for European-Americans Door-to-door survey in Taiwan

Prevalence of PD =119/100,000

Similar to that of a white population and much higher than that of previous studies of Asian

populations

Ethnicity

Differences in findings Suggest environmental factors more important than racial factors Further studies needed

Other factors?

Differences in access to healthcare?

Ethnicity• The disease was once thought to affect

primarily whites, but recent studies have demonstrated equal prevalence in African Americans and whites living in the same geographic area.• Comparative epidemiologic studies performed

in various major cities have yielded contradictory information.• Variations in the prevalence of the disease in

individual racial groups in different geographic areas have suggested an increased risk associated with rural living.

Time

Hard to evaluate Few studies that track over long period of time Studies might use different methods or have different diagnostic criteria Two studies different conclusions Greater awareness - well-known people have developed PD

Time

Study in Olmsted, Minnesota1935-1988

Tracked number of people diagnosed with PD each year

1935-1944: 9.2/100,000 diagnosed

1975-1984: 16.3/100,000 diagnosed

Time

NIH study of world-wide PD trends Statistically controlled for age differences Concluded that the prevalence and incidence of PD appear to have remained unchanged over the past 40 years.

Definition of a risk factor- Risk factor is anything that increases your chances of getting

sick or having a problem. The onset of Parkinson’s disease is a multi factorial process. However even if you have several known risk factors, you might still not have PD(Parkinson’s disease).

In July 2004, THE NATIONAL INSTITUTE OF HEALTH (NIH)reported that more than two dozen genetic risk factors involved in PD have been identified, among which 6 were such which were reported for the first time. In a small number of cases worldwide, there is a strong inheritance pattern for the disease. In such cases the development of the disease is basically due to an environmental toxin present or trauma or an illness.

• Age

• Sex

• Family history

• Declining oestrogen level

• Agricultural work

• Levels of B vitamin folate

• Head trauma

• Free radicals

FACTORS ASSOCIATED WITH FACTORS ASSOCIATED WITH PARKINSON’S DISEASEPARKINSON’S DISEASE

Advancing age- Cases of young age development of the disease

has been noticed although the actual symptoms occurs at a later age and keeps on getting worse as one gets older. Researches have shown that people with Parkinson’s have neural defects which keeps getting worse as one gets older.

FACTORS ASSOCIATED WITH FACTORS ASSOCIATED WITH PARKINSON’S DISEASEPARKINSON’S DISEASE

Sex- Males are at higher risk of getting Parkinson’s disease than

females. Reason for this being that males are most exposed to factors such as-head trauma or environmental toxins. Researches have shown that oestrogen have neuro-protective functions hence females are at lesser risk.

FACTORS ASSOCIATED WITH FACTORS ASSOCIATED WITH PARKINSON’S DISEASEPARKINSON’S DISEASE

Familial history- Having one or more closely related family member affected

by the disease increases your risk of developing the disease too. But to a minimal degree. This lends support to the idea that Parkinson’s Disease has a genetic link.

FACTORS ASSOCIATED WITH FACTORS ASSOCIATED WITH PARKINSON’S DISEASEPARKINSON’S DISEASE

Declining oestrogen level-• As a woman attains menopausal age, the levels of

oestrogen in the body decreases.• As it known that oestrogen has neuro-protective functions,

low levels of oestrogen might result in the development of the disease. Women not opting for hormone replacement therapies are particularly ar risk.

FACTORS ASSOCIATED WITH FACTORS ASSOCIATED WITH PARKINSON’S DISEASEPARKINSON’S DISEASE

Agriculture work- Agricultural work expose you to several environmental toxins

which may cause PD as they inhibit dopamine production and promote free radical damage. Farmers are at high risk due use of pesticides and other chemicals.

FACTORS ASSOCIATED WITH FACTORS ASSOCIATED WITH PARKINSON’S DISEASEPARKINSON’S DISEASE

Low levels of B vitamin folate- Researchers have studied that mice which have a low level of

this vitamin develop severe Parkinson’s Disease whereas mice with a normal level do not develop.

FACTORS ASSOCIATED WITH FACTORS ASSOCIATED WITH PARKINSON’S DISEASEPARKINSON’S DISEASE

Head trauma- Recent studies have found a link between injury to the head,

neck and cervical spine and Parkinson’s disease. In 2007,60 patients show trauma-induced upper cervical damage. Some patients remembered a particular incident others did not. In some cases Parkinson’s symptoms took decades to appear.

FACTORS ASSOCIATED WITH FACTORS ASSOCIATED WITH PARKINSON’S DISEASEPARKINSON’S DISEASE

Free radicals- Usually free radicals are formed in body and brain but they

eventually they are flushed out of the body due to mechanisms of the brain and body. People with Parkinson’s disease don’t have such mechanisms to flush out such free radicals. Environmental toxins contribute to abnormal increase in free radicals and increase in risk of Parkinson’s Disease.

THANK YOU