Table 3.

Association between severity of depressive symptoms and chronic knee pain

	Model 1		Model 2		Model 3
	OR (95% CI)	P value	OR (95% CI)	P value	OR (95% CI)	P value
Diagnosis of depressive symptoms
No	1		1		1
Yes	3.553 (2.558 to 4.935)	<0.0001	2.722 (1.844 to 4.017)	<0.0001	2.333 (1.605 to 3.391)	<0.0001
Levels of depressive symptom
None (0–4)	1		1		1
Mild (5–9)	3.715 (2.687 to 5.138)	<0.0001	3.266 (2.35 to 4.541)	<0.0001	2.944 (2.112 to 4.103)	<0.0001
Moderate (10–14)	4.525 (2.964 to 6.909)	<0.0001	3.619 (2.233 to 5.865)	<0.0001	3.211 (1.977 to 5.217)	<0.0001
Moderately severe (15–19)	4.124 (2.256 to 7.539)	<0.0001	2.805 (1.553 to 5.066)	0.0007	2.43 (1.355 to 4.359)	0.0031
Severe (20–27)	6.93 (2.519 to 19.068)	0.0002	5.109 (1.606 to 16.257)	0.006	4.552 (1.489 to 13.92)	0.0082
P value for trend		<0.0001		<0.0001		<0.0001

Logistic regression analysis with complex sampling design was performed by adjusting for covariates. Individuals with PHQ-9 scores >10 were considered to have depressive symptoms. Levels of depressive symptom were divided into five quartiles: none (0–4), mild (5–9), moderate (10–14), moderately severe (15–19) and severe (20–27) according to the PHQ-9 score. Model 1 was unadjusted ORs. Model 2 was adjusted by age and sex. Model 3 was fully adjusted by age, sex and other environmental factors, such as smoking, alcohol consumption, educational level, household income, physical activity, duration of sleep and comorbidities.

PHQ-9, Patient Health Questionnaire-9.