Differences in physical and psychological health in patients with chronic low back pain: a national survey in general Spanish population.

To estimate the prevalence of diagnosed and undiagnosed chronic low back pain (CLBP-D and CLBP-UD, respectively) in the general adult population in Spain and to compare the characteristics of these two groups with subjects without CLBP symptoms (No-CLBP). To establish CLBP-D patient sub-groups according to their self-perceived health status, mental health, level of pain and the impact of their pain on daily activities. Data were obtained from the National Health Survey of Spain 2017 with a sample of 23,089 adults. Three groups were defined: CLBP-D, CLBP-UD and No-CLBP. In the CLBP-D group, a cluster analysis was performed to identify sub-groups. A multinomial regression model was constructed to determine the factors associated with each of the sub-groups identified. The prevalence of CLBP-D was 22% (95% CI 21.5-22.5) and that of CLBP-UD was 1.4% (95% CI 1.2-1.5). CLBP-D was more common in middle-aged females with a low educational level. They have a worse perceived health status, report more comorbidities, have worse mental health and more limitations in comparison with the populations without CLBP and with CLBP-UD. Three sub-groups of CLBP-D subjects were identified. Women and older subjects with a lower educational level, more occupational stress, less social support and with more physical limitations were the most likely subjects to be included in the group worst-affected. There is a high prevalence of CLBP among the adult population in Spain. Occupational stress and a lack of social support are common factors among subjects' worst-affected of CLBP-D and identifying the subjects with these risks is therefore a recommended strategy for improving the healthcare provided to CLBP patients.