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. Author manuscript; available in PMC: 2022 Apr 1.
Published in final edited form as: Arthritis Care Res (Hoboken). 2021 Mar 13;73(4):566–573. doi: 10.1002/acr.24151

Table 2.

Total, Direct, and Indirect Effect of Radiographic Knee OA Only, Knee Pain Only, and Symptomatic Knee OA on All-cause Mortality

Neither Radiographic Knee OA nor Knee Pain (n=1,139) Radiographic Knee OA Only (n=1,117) Knee Pain Only (n=856) Symptomatic Knee OA (n=1,387)
Number of Death 72 72 43 95
Deaths per 1000 Person-years (95% CI) 9.4 (7.4 to 11.8) 14.1 (11.1 to 17.8) 7.9 (5.7 to 10.6) 15.7 (12.7 to 19.2)
Total Effect, HR (95% CI) 1.0 (reference) 2.6 (1.8 to 3.6) 0.9 (0.6 to 1.3) 2.6 (1.9 to 3.6)
Total Effect, HR (95% CI) * 1.0 (reference) 2.0 (1.4 to 2.9) 0.9 (0.6 to 1.4) 2.2 (1.6 to 3.1)
Disability Score
  Direct, HR (95% CI) * 1.0 (reference) 2.0 (1.7 to 2.4) 0.9 (0.7 to 1.1) 1.9 (1.6 to 2.3)
  Indirect, HR (95% CI) * 1.0 (reference) 1.0 (0.9 to 1.2) 1.0 (0.9 to 1.2) 1.1 (1.0 to 1.4)
  Mediation effect (%) - 2.0 Not same direction 22.4
PCS of QoL
  Direct, HR (95% CI) * 1.0 (reference) 2.0 (1.7 to 2.4) 0.9 (0.7 to 1.1) 1.9 (1.6 to 2.2)
  Indirect, HR (95% CI) * 1.0 (reference) 1.0 (0.8 to 1.2) 1.1 (0.9 to 1.3) 1.2 (1.0 to 1.4)
  Mediation effect (%) - 0.0 Not same direction 26.5
MCS of QoL
  Direct, HR (95% CI) * 1.0 (reference) 2.0 (1.7 to 2.4) 0.9 (0.7 to 1.2) 2.2 (1.9 to 2.6)
  Indirect, HR (95% CI) * 1.0 (reference) 1.0 (0.8 to 1.2) 1.0 (0.8 to 1.2) 1.0 (0.8 to 1.2)
  Mediation effect (%) - 0.0 Not same direction 0.0
Oral Pain Medications Use
  Direct, HR (95% CI) * 1.0 (reference) 2.0 (1.7 to 2.4) 0.9 (0.7 to 1.1) 2.1 (1.7 to 2.5)
  Indirect, HR (95% CI) * 1.0 (reference) 1.0 (0.9 to 1.2) 1.0 (0.9 to 1.2) 1.1 (0.9 to 1.3)
  Mediation effect (%) - 2.0 Not same direction 12.0

n, number; OA, osteoarthritis; CI, confidence interval; HR, hazard ratio; PCS, physical component summary score; MCS, mental component summary score; QoL, quality of life.

*

Adjusted for age, race, sex, body mass index, education level, weekly alcohol consumption, smoking habits, history of knee injury, comorbidities, depressive symptoms and widespread pain.