Prevalence of Cerebral Palsy

Cerebral Palsy is the most common of all childhood disabilities, affecting approximately three live births out of every thousand in the United States. To truly understand how widespread the condition is among children and adults in the United States – or in a particular community – it helps to understand the difference between incidence and prevalence.

How common is Cerebral Palsy?

Studies over the past several decades have provided the following statistics, commonly quoted in the United States:

• About 764,000 children and adults currently have Cerebral Palsy
• About 500,000 children under age of 18 currently have Cerebral Palsy
• About two to three children out of every 1,000 have Cerebral Palsy (United States studies have yielded rates as low as 2.3 per 1,000 children to as high as 3.6 per 1,000 children)
• About 10,000 babies born each year will develop Cerebral Palsy
• Around 8,000 to 10,000 babies and infants are diagnosed per year with Cerebral Palsy
• Around 1,200 to 1,500 preschool-aged children are diagnosed per year with Cerebral Palsy

The difference between prevalence and incidence of Cerebral Palsy

The terms “prevalence” and “incidence,” are often incorrectly interchanged. At first glance, it would appear little difference exists, but, used correctly, prevalence indicates the number of individuals living with a particular condition on a specified date. For example, on December 31, 2009 there were 20,000 individuals diagnosed with the condition. Incidence relates to the number who are diagnosed with the condition during a specified time frame. For example, 28 children a year are diagnosed with the condition, or 14 children are diagnosed with the condition every six months.

Prevalence

Prevalence, usually expressed as a number or ratio, is the total number of people with Cerebral Palsy in a certain place – the United States – at a given date. Prevalence statistics answer the question, “How many people in the United States have Cerebral Palsy?” For instance, it is estimated there are 764,000 children and adults living with Cerebral Palsy in the United States. The number of individuals with Cerebral Palsy is then compared to the total population. For example, 2.3 to 3.6 (studies vary) of every 1,000 individuals in the United States have Cerebral Palsy. Researchers can compare prevalence in the United States with prevalence statistics in other countries. Or, they compare the fluctuation in prevalence from year to year.

Incidence

Incidence, usually expressed as a rate, looks at the number of children born with Cerebral Palsy within a specific time period and answers the question “How often does Cerebral Palsy occur?” The incidence rate, then, discerns the number of new cases diagnosed during a specific time. For example, in the United States, it is estimated approximately 8,000 to 10,000 babies born each year will develop Cerebral Palsy.

Both methods are useful in similar, yet different, ways.

Worldwide efforts are being made to share incidence and prevalence studies. There is much to be learned by analyzing studies and comparing study results from study-to-study, community-to-community, among specific demographic groups, and across national borders. This type of data will indicate where conditions are more prevalent, where prevention awareness campaigns can be more useful, and where health care resources can be improved. Government agencies use the statistics to monitor health conditions while appropriating funds for assistance where needed.

Prevalence and incidence statistics provide those touched by Cerebral Palsy with an understanding of how widespread Cerebral Palsy is. They may feel some degree of comfort in knowing they are not alone.

Four prominent studies
conducted within the U.S.

Since the mid-1980s, researchers have conducted a number of studies aimed at determining the prevalence and incidence of Cerebral Palsy within the United States. Many were performed through or for the Centers for Disease Control and Prevention (CDC), which is based in Atlanta, Georgia.

The results of the studies varied, but useful generalizations can provide an understanding of how many individuals with Cerebral Palsy live in the United States, and which types and forms of Cerebral Palsy are most common. Most of the studies performed on prevalence and incidence in the United States, however, are now outdated at nearly a decade old. The studies were also performed in a small test market with results extrapolated to apply to the nation as a whole.

According to these studies, overall:

• Cerebral Palsy occurs in 2.3 to 3.6 out of every 1,000 children
• Spastic Cerebral Palsy is most common, making up 61 percent to 76.9 percent of all Cerebral Palsy cases

Study details and findings, descending in chronological order beginning with most recent, include the following.

2002 STUDY

“Prevalence of Cerebral Palsy in 8-Year-Old Children in Three Areas of the United States in 2002: A Multisite Collaboration”

(Based on Centers for Disease Control and Prevention Metropolitan Atlanta Developmental Disabilities Surveillance Program, investigators from the Autism and Developmental Disabilities Monitoring Network conducted the surveillance.)

In the first multi-state study, prevalence of Cerebral Palsy among 8-year-old children was surveyed in northern Alabama, metropolitan Atlanta, and southeastern Wisconsin. Data from 114,897 children was analyzed. Cerebral Palsy occurred at a rate of 3.6 cases per 1,000 children. Spastic Cerebral Palsy was the most common form, accounting for 76.9 percent of all cases.

This study includes Cerebral Palsy acquired after birth.

The study relied on documentation as the source of data. The Alabama and Wisconsin sites didn’t have access to school records, perhaps one of the best methods of identifying children with disabilities, a factor which may have resulted in underreporting. Conversely, researchers claim to have erred on the side of a Cerebral Palsy diagnosis when reviewing ambiguous medical records, which may have inflated numbers.

Spastic Cerebral Palsy was further divided into subgroups:

• Unilateral Spastic Cerebral Palsy accounts for 30 percent of the spastic Cerebral Palsy cases
  • Spastic hemiplegia accounts for 22.6 percent
  • Spastic monoplegia accounts for 0.5 percent

• Bilateral Spastic Cerebral Palsy accounts for 69 percent of spastic Cerebral Palsy cases
  • Spastic diplegia accounts for 22.4 percent
  • Spastic quadriplegia accounts for 25.0 percent
  • Spastic triplegia accounts for 1.2 percent
  • Spastic NOS accounts for 5.3 percent

• Unaccounted Spastic Cerebral Palsy accounts for 0.7 percent of spastic Cerebral Palsy cases

1996 AND 2000 COMPARISON

“Prevalence of Four Developmental Disabilities Among Children Aged 8 Years – Metropolitan Atlanta Developmental Disabilities Surveillance Program, 1996 and 2000”

Two similar studies were conducted in the five-county metropolitan Atlanta area in 1996 and 2000. The studies also surveyed 8-year-old children with Cerebral Palsy, and additionally tracked four other developmental disabilities. The 1996 study found a higher prevalence – 3.6 cases per 1,000 children – than the 2000 study – 3.1 cases per 1,000 children. Data was collected via educational records from nine public school systems and alternative education sources, plus clinical records from private and public medical facilities.

Some question the validity of the 1996 study, as the higher prevalence in 1996 is out of sync with the 2000 and the 1992 studies. In comparison to the other studies, the records used were not adequately tracked, and could have led to errors.

However, the 1996 prevalence is the same as the 2002 study. It is noteworthy that while each study produced helpful statistics, none provided a definitive, clear answer about prevalence and incidence of Cerebral Palsy. Future studies will continue to clarify past results.

1991-1994 STUDY

“A population-based study of the recurrence of developmental disabilities”

(Metropolitan Atlanta Developmental Disabilities Surveillance Program, 1991-1994)

In a different type of study, the rate that one mother gave birth to two or more children with Cerebral Palsy (and/or other development disabilities) was tallied for the period between 1981 and 1991. The purpose was to determine if having a child with a developmental disability increased the likelihood of a future child also being born with a developmental disability.

The study determined that mothers who give birth to a child with a developmental disability are more likely to give birth to another child with a developmental disability. For all children born, the study determined a 2 percent chance of the child having a developmental disability. For mothers who have already given birth to a child with a developmental disability, the rate rises to 3 percent to 7 percent, depending on the previous disability.

1985-1987 STUDY

“A multiple-source method for studying the prevalence of developmental disabilities in children: the Metropolitan Atlanta Developmental Disabilities Study”

In one of the first of its kind, this two-year study accessed school records, and other additional sources, to indentify 10-year-old children with Cerebral Palsy and other developmental disabilities in the five-county Atlanta area. This study found that Cerebral Palsy occurred in 2.3 out of every 1,000 children.

Using school records allows government agencies to identify and accommodate children with disabilities. The multi-source method provided researchers with the capability to confirm diagnosis. Because of its strengths, this study became the model for subsequent studies.

Methodology: Nine sources from five counties were reviewed to identify 10-year-old children with disabilities. The multiple sources allowed researchers to confirm diagnosis, as opposed to relying on only one source.

Findings:

A total of 89,534 children were studied.

• There were, on average, 2.3 cases of Cerebral Palsy per 1,000 children
• A total of 204 children were diagnosed with Cerebral Palsy

Of those 204 children diagnosed with Cerebral Palsy:

• 61 percent had spastic Cerebral Palsy
• 5 percent had non-spastic Cerebral Palsy
• 33 percent had unspecified Cerebral Palsy

How to interpret Cerebral Palsy studies

When reading studies about Cerebral Palsy it is helpful to understand the benefits and the drawbacks of how the data was collected and interpreted. All studies have strengths and weaknesses. Researchers must sometimes make choices that may affect the data. This does not mean the study is invalid but instead provides a context in which the data should be understood.

For instance, the 2002 multi-site survey chose sites based on the facilities’ capability to conduct the research. Though understandable, this means the three sites were not chosen because they best represented the entire U.S. population. In addition, this study was not able to compare the same type of records in all three geographical areas. This makes comparisons difficult. It can also impact data interpretation.

Another factor in Cerebral Palsy studies is the age of the children. Cerebral Palsy is a condition that sometimes is not diagnosed until the age of five. When studying 3-year-olds it could be assumed that some have not yet been diagnosed. However, studies that look at 8- or 10-year-old children might miss those that had Cerebral Palsy, but died at birth. The recent studies conducted by the CDC have focused on 8-year-old children as data indicates that this is when the prevalence of Cerebral Palsy peaks, thus giving the most accurate count.

Babies that die during labor or delivery or who do not survive to term are rarely included in any sort of studies not specifically related to infant mortality. Children who die at or before birth are often listed with low birth weight or prematurity as cause of death, potentially leaving a case of Cerebral Palsy or asphyxiation undetected.

Since those in the medical field debate about Cerebral Palsy acquired after birth, the actual diagnosis of Cerebral Palsy was another significant factor in the studies. For instance, if a child is not born with Cerebral Palsy, but acquires the condition due to an accident, shaken baby syndrome, or a closed head injury, he or she may develop the symptoms of Cerebral Palsy and may be treated for CP, but these children are often not labeled as having the condition. Some studies do not include these cases in their findings, but depending on how data from the study is used – to ascertain the need for benefit programs and government assistance, for example – excluding these children would grossly under report prevalence.

Some compensate by applying the “No CP” label, but many researchers historically chose to exclude all Cerebral Palsy acquired after birth. Most current studies, however, have reversed this trend by including the cases, but designating them appropriately so the data can be utilized for specific needs.

RESOURCES

Prevalence and incidence

Government and non-government organizations, or NGOs, perform and sponsor studies on disabilities and impairments. The U.S. Department of Health and Human Resources (HHR) is the leading national agency dedicated to protecting the health of all Americans, while providing essential human services. HHR maintains several divisions that focus on research, prevention, safety, health, and welfare, including those touched by Cerebral Palsy.

Centers for Disease Control and Prevention, or CDI

The Centers for Disease Control and Prevention is a division of the U.S. Department of Health and Human Services, an organization dedicated to marketing communications for the protection of health and disease control, injury and disability. The CDC has conducted surveillance of birth defects, including the following three initiatives:

• Metropolitan Atlanta Development Disabilities Surveillance Program (MADDSP) monitors five developmental disabilities, including Cerebral Palsy, in Atlanta, Georgia. It is the model for many other programs in U.S.
• Autism and Developmental Disabilities Monitoring Network (ADDM) tracks children with autism spectrum disorders and Cerebral Palsy.
• Centers of Excellence for Autism and Developmental Disabilities Research and Epidemiology (CADDRE) also study autism and Cerebral Palsy in children.

The Department of Health and Human Resources, or HHR

Other important HHR divisions:

• National Institute of Neurological Disorders, or NINDS, is currently researching traumatic events, genetic defects and treatment protocols in Cerebral Palsy.
• National Institute of Health, or NIH, known as one of the world’s largest research centers, NIH has the largest source of funding for medical research worldwide.
• Center on Birth Defects and Developmental Disabilities, or NCBDDD, part of the U.S. Centers for Disease Control and Prevention. The center focuses on protecting people who are at increased health risk, including those with disabilities.
• The Health Resources and Services Administration, or HRSA, is a U.S. agency dedicated to improving access to health care services for people who are uninsured, isolated, or medically vulnerable.
• Maternal and Child Health Bureau, or MCHB, is focused on improving the health of all mothers and children by training providers, conducting public education and outreach, and providing support services for children with special healthcare needs. The MCHB also offers injury prevention, newborn screening and childcare health and safety programs.

U.S. Non-Government Organizations, or NGOs

Non-government organizations that perform or fund research, as well as advocate for and assist those with Cerebral Palsy, include:

• March of Dimes is the leading nongovernment agency on pregnancy and baby health. They are currently focused on preventing birth defects, premature birth and infant mortality.
• Easter Seals is a non-profit, community-based health agency focused on assisting those with disabilities attain greater independence.
• United Cerebral Palsy (UCPA) is an international network of independent non-profit chapters that provides information, advocacy and direct care for those with developmental disabilities.
• Cerebral Palsy International Research Foundation is a non-profit organization focused on funding research and educational initiatives directly related to the discovery of cause, cure and evidence-based care for those with Cerebral Palsy and related developmental disabilties.

International Agencies

International agencies based outside of the U.S. promoting Cerebral Palsy research, include:

• World Health Organization (WHO) is the United Nations’ coordinating authority for health and leadership on global health initiatives. They shape research agendas, set norms and standards, and articulate evidence-based policy options while monitoring and assessing health trends.
• Surveillance of Cerebral Palsy in Europe (SCPE) is a collaborative network in 14 centers in 8 countries across Europe developing a central database of children with Cerebral Palsy. SCPE monitors trends, disseminates information, and provides a collaborative framework.