Do politics affect prevalence? An overview and the case of cerebral palsy

Many factors must be considered when assessing estimates of prevalence, including research methods and quality of the work by the research team. Broad social and political forces also influence estimates of prevalence, as seen in the case of autism and intellectual disability. Indeed, researchers themselves may be influenced by broader sociopolitical factors in ways that they do not recognize. To further explore the relationship of prevalence to sociopolitical factors, we reviewed the historical prevalence of cerebral palsy (CP) (as a proxy for physical disability) in the late 20th century. We hypothesized that increased awareness of physical impairments associated with the disability rights movement of the 1970s would increase the prevalence of CP, primarily because of changes in case definition. Although prevalence of CP did rise slightly in the 1980s, we conclude that this change is better explained by increased survival of low birth weight infants, which is only indirectly related to the disability rights movement.