What is "normal" disability? An investigation of disability in the general population.

Many studies have investigated the highly relevant association between pain and disability in clinical groups using the Pain Disability Index (PDI). To interpret these results, knowledge of disability in the general population is crucial. Moreover, to investigate criterion validity of the PDI, the influence on health care utilisation (HCU) is of special interest. In the present study, a broadened version of the PDI was psychometrically evaluated with a large representative sample of the general population. The independent impact of disability on HCU was also investigated. A representative sample of the German general population (N=2510) was screened for disability, somatic complaints, mental health (PHQ) and HCU. Following a psychometric evaluation of the PDI, data are provided about the distribution of disability in the general population. For the prediction of HCU, stepwise linear regression analysis was calculated. The psychometric evaluation of the PDI revealed a one-factor solution, high reliability, and satisfactory construct validity. Percentage scores for the distribution of disability are provided for those people reporting at least one pain/somatic symptom. These data allow a better description of disability in clinical samples. Somatic complaints, disability, unemployment or retirement, depression and anxiety explained 26% of the variance for HCU. The PDI is an economical, reliable and valid self-rating instrument for assessing disability caused by physical symptoms. HCU in the general population is determined by the number and severity of somatic complaints and also by disability. Symptoms and disability play a crucial but somewhat independent role.