Trends in the Prevalence of Cerebral Palsy in a Population-Based Study

 Sarah Winter, MD^*, Andrew Autry, PhD, Coleen Boyle, PhD and Marshalyn Yeargin-Allsopp, MD Department of Pediatrics, Emory University, Atlanta, Georgia;
National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia PEDIATRICS Vol. 110 No. 6 December 2002, pp. 1220-122

Objective. To determine trends in the prevalence of congenital cerebral palsy (CP) over a 16-year period for 1-year survivors using a large, population-based surveillance program.

 Methods. We determined birth weight-specific trends in the prevalence of CP in live birth and 1-year survivor cohorts of children in a 5-county metropolitan Atlanta area for the periods from 1975–1977, 1981–1985, and 1986–1991. We ascertained children with CP in metropolitan Atlanta by record review as part of an ongoing developmental disability surveillance program conducted by the Centers for Disease Control and Prevention and the Georgia Department of Human Resources. A total of 110, 262, and 443 cases of congenital CP were identified for the birth years 1975–1977, 1981–1985, and 1986–1991, respectively. Data were analyzed by birth weight, race, subtypes of CP, and whether the CP existed as an isolated disability or was accompanied by another disability.

 Results. There was a modest increase in the overall prevalence of congenital CP from 1.7 to 2.0 per 1000 1-year survivors during the period from 1975–1991. This trend was primarily attributable to a slight increase in CP in infants of normal birth weight—CP rates in moderately low and very low birth weight infants did not show consistent trends. There was an increase in the proportion of children who had CP and no other disabilities that was most apparent in infants of normal birth weight from 17% in 1975–1977 to 39% in 1986–1991. For children weighing <1500 g, the proportion of children with spastic diplegic CP increased over time (7% of cases in 1975–1977, 36% in 1985–1988, and 32% in 1986–1991). Conclusions. In the only ongoing population-based study of CP in the United States, there has been a modest increase in the prevalence of CP in 1-year survivors born from 1975–1991. This increase however was seen only in infant survivors of normal birth weight. No change was seen in the trends in CP prevalence in low birth weight and very low birth weight infant based on infant survivors.

 Key Words: cerebral palsy • epidemiology • trends • prevalence • developmental disability Abbreviations: CP, cerebral palsy • CDC, Centers for Disease Control • Prevention

Received for publication Feb 21, 2002; accepted Jul 30, 2002.

A review of “Trends in the Prevalence of Cerebral Palsy in a Population-Based Study” by Nigel Paneth, MD, MPH, Project Director, Cerebral Palsy Outreach Network. 

1. What is the purpose of this study?

The authors measure the frequency of CP in a region of the United States, and ask whether it has changed over time  

2. How was the study done?

The 5-county metropolitan Atlanta region has been the site of ongoing surveillance of CP and other developmental disorders since 1985. This paper reviews the number of children with CP identified in three groups of births – those that took place in 1975-77, in 1981-85, and in 1986-91. The first group of children was identified at age 10, and the last two groups were identified between ages 3-10. Children with CP were identified from medical records in hospitals, private practices, clinics, early intervention programs, social service agencies and the school system.

3. What are the main findings?

CP seems to be slightly on the increase. In children born in the late 1970’s the CP prevalence rate was 1.7 per thousand live births.  For children born in the early 1980’s the figure was 1.8, and for late 1980’s births, 2.0 per thousand births.   An increase was seen both for small babies (< 3 lbs at birth) who are at high risk for CP, and for normal weight infants.  

4. What are the strengths of this study?

 It is very hard to find good data in the US on the frequency of CP.  Metropolitan Atlanta is one of just two regions in the country in which CP has been regularly counted (the other is the Bay area of San Francisco), and the Atlanta program is more comprehensive. The authors (who are from the CDC) are very experienced in doing surveillance for CP and other developmental disorders.

5. What are the weaknesses of this study?

 The children with CP were not actually examined by the authors, but reliance was placed on existing medical records. However, the same case definition was applied and the same qualified individual reviewed all cases throughout the study. The first wave assessed at age 10, the next two waves at younger ages, and this could have produced more cases in the later time periods. No births since 1992 were evaluated, so it is too soon to see whether things have changed for births in the 1990’s.  

6. How important are these results?

 Most studies of the frequency of CP are from Europe and Asia, as there are few ongoing CP registries in the US. Those studies have tended to find increases in CP in recent years among very small babies (due to improving survival) but stability, and sometimes small declines, in CP among babies of normal weight.  This study is unusual in finding an increase in CP in infants of normal weight.  However, the increase was small. Perhaps the most sobering conclusion is that in spite of steadily improving prenatal and perinatal care in recent decades, we have yet to see a decline in CP. Clearly we have a lot to learn about the true causes of CP and how to address them.