The relationship between pain severity and patient-reported outcomes among patients with chronic low back pain in Japan

Objective: The aim of this study was to quantify the impact of pain severity on patient-reported outcomes among individuals diagnosed with chronic low back pain in Japan. Methods: Data were provided by the 2012 Japan National Health and Wellness Survey (N=29,997), a web-based survey of individuals in Japan aged >= 18 years. This analysis included respondents diagnosed with low back pain of >= 3-month duration. Measures included the revised Medical Outcomes Study 36-Item Short-Form Survey Instrument, the Patient Health Questionnaire-9, the Generalized Anxiety Disorder-7 scale, the Work Productivity and - Activity - Impairment: General Health questionnaire, and self-reported all-cause health care visits (6 months). Generalized linear models were used to assess the relationship between outcomes and severity of pain in the past week as reported on a numeric rating scale ranging from 0 (no pain) to 10 (pain as bad as you can imagine), controlling for length of diagnosis, sociodemographics, and general health characteristics. Results: A total of 290 respondents were included in the analysis; mean age was 56 years, 41% were females, and 56% were employed. Pain severity was 3/10 for the first quartile, 5/10 for the median, and 7/10 for the third quartile of this sample. Increasing severity was associated with lower scores for mental and physical component summaries and Short-Form 6D health utility, higher depression (Patient Health Questionnaire-9) and anxiety (Generalized Anxiety Disorder-7) scores, greater absenteeism and presenteeism, greater activity impairment, and more health care provider visits (all P < 0.0001). Conclusion: The impact of chronic low back pain on health-related quality of life, depression and anxiety symptoms, impairment to work and daily activities, and health care use increases with the severity of pain. Interventions reducing the severity of pain may improve numerous health outcomes even if the pain cannot be eliminated.