A nationwide study of chronic pain prevalence in the general spanish population: identifying clinical subgroups through cluster analysis.

OBJECTIVE: This study aims to assess the prevalence of chronic pain, its characteristics, and its impact on the general Spanish population. Also, to establish chronic pain patient subgroups according to the characteristics of pain and to identify variables specifically associated with each subgroup.
DESIGN: Telephone-based, cross-sectional nationwide study.
SUBJECTS: A sample of 1,957 individuals representative of the Spanish population.
METHODS: Data were collected through telephone interviews. A subject was considered to have chronic pain if they had suffered pain (at least 4 days a week) during the last 3 months. The subjects were divided into two subgroups through a cluster analysis, and a regression model was established to determine the variables most specifically associated with these subgroups.
RESULTS: The prevalence of chronic pain was 16.6% (95% confidence interval: 14.9-18.3) and among these subjects, more than 50% referred to limitations in their daily activities, 30% felt sad and/or anxious, and 47.2% indicated that their pain was affecting their family life. Two subgroups of subjects with pain were identified: 1) characterized by generalized pain in more than one location and of a long evolution (150 months); and 2) characterized by pain localized to only one site with a shorter duration (100 months). Individuals who felt anxious because of their pain and those who considered that their pain was affecting their family were more likely to belong to group 1.
CONCLUSIONS: Pain affects an important proportion of the Spanish adult population and that it has a strong personal impact. Two pain groups were clearly distinguished by their clinical characteristics. Wiley Periodicals, Inc.