Recent trends in cerebral palsy survival. Part I: period and cohort effects

To determine whether the trend of improved survival among individuals with cerebral palsy (CP) in California during the 1980s and 1990s has continued during the most recent decade.

In an observational cohort study we evaluated individuals with CP, aged 4 years and older, who were clients of the California Department of Developmental Services. Medical diagnoses, functional disabilities, and special health care requirements were assessed with Client Development Evaluation Reports made between 1983 and 2010. Trends in birth cohort survival were analyzed with Kaplan-Meier curves and Cox regression. Calendar year period effects were analyzed with Poisson regression.

A total of 51,923 persons with CP (28,789 males [55%], 23,134 females [45%]; mean age 14y 11mo, SD 14y 1mo, range 4y 0mo to 96y 10mo) collectively contributed 662,268 years of follow-up. There were 7690 deaths for an overall mortality rate of 11.6 per 1000 persons per year. No significant birth cohort effects on survival were observed in 4-year-olds who had no severe disabilities. By contrast, children who did not lift their heads in prone position who were born in more recent years had significantly lower mortality rates (Cox hazard ratio 0.971, p<0.001) than those with comparable disabilities born earlier. With regard to calendar year period effects, we found that age-, sex-, and disability-specific mortality rates declined by 1.5% (95% CI 0.9-2.1) year-over-year from 1983 to 2010. The estimate increased to 2.5% (95% CI 1.9-3.1) per year when we additionally controlled for tube-feeding status. Mortality rates in tube fed adolescents and adults, ages 15 to 59 years, declined by 0.9% (95% CI, 0.4-1.4) per year. No improvement was observed for adolescents or adults who fed orally or for those over age 60. In fact, the ratio of age-specific mortality rates for these latter groups to those in the general population, increased by 1.7% (95% CI 1.3-2.0) per year during the study period.

The trend toward improved survival has continued throughout the most recent decade. Declines in CP childhood mortality are comparable to the improvements observed in the United States general population (i.e. the mortality ratio in childhood has remained roughly constant over the last three decades). In contrast, the mortality ratio for most adolescents and adults with CP, relative to the general population, has increased.