Association between severity of depressive symptoms and chronic knee pain in Korean adults aged over 50 years: a cross-sectional study using nationally representative data

OBJECTIVES: To identify the association between the presence and severity of depressive symptoms and those of chronic knee pain. DESIGN: A retrospective cross-sectional study. PARTICIPANTS: We used data from the sixth Korea National Health and Nutrition Examination Survey (KNHANES VI-2) performed in 2014. Overall, 7550 patients were included in the KNHANES VI-2. OUTCOME MEASURES: Participants were asked whether they had chronic knee pain, and each answer was either ‘yes’ or ‘no’. Patient Health Questionnaire-9 (PHQ-9) was used as a screening tool for depressive symptoms, and PHQ-9 scores of 10 or higher was classified as the depressed group. In total, 527 patients reported that they had pain in their knee, of whom 91 also had depressive symptoms. RESULTS: The prevalence of chronic knee pain in the Korean population aged over 50 years was 19.8%. Multiple logistic regression was conducted after adjustment for sex, age, smoking, alcohol drinking, education level, household income, physical activity, sleep duration and comorbidity. The analysis revealed a significant association between depressive symptoms and chronic knee pain (adjusted OR=2.333, p<0.001). In contrast, the severity of depressive symptoms was linearly correlated with the intensity of chronic knee pain (p for trend <0.001). In participants with no chronic knee pain (Numerical Rating Scale; NRS=0) or mild chronic knee pain (NRS=1–4), the prevalence of moderate and severe depressive symptoms was 3.4% and 0.6%, respectively. However, in those with severe chronic knee pain (NRS=8–10), there was a higher prevalence of moderate and severe depressive symptoms (10.1% and 5.8%, respectively) (p<0.001). CONCLUSIONS: A strong association was observed between the presence and severity of depressive symptoms and the presence of chronic knee pain. The association became stronger with higher levels of depressive symptoms, indicating a positive correlation between depressive symptoms severity and chronic knee pain.