Table 3.
Multivariable-adjusted mean (95% CI) physical function scores, muscle strength and specific strength stratified according to low versus high inflammatory status (non-linear models)
| Physical function & strength | Markers of inflammation | Inflammatory Statusa | Mean Difference | |
|---|---|---|---|---|
| Low | High | |||
| Six-minute walk test [6MWT]: distance (m) | hs-CRP (mg/ L)b | 496 (474, 518) | 458 (444, 473) | 38 (11, 65) * |
| Composite Inflammation Scorec | 488 (472, 504) | 448 (430, 466) | 40 (15, 64) * | |
| Gait speed (m/s) | Composite Inflammation Scorec | 1.05 (1.01, 1.10) | 1.04 (0.99, 1.09) | 0.02 (−0.05, 0.08) |
| Chair sit and reach [CSR] (cm) | TNFα (pg/ ml) | −3.8 (−6.3, −1.3) | −4.2 (−6.8, −1.6) | 0.4 (−3.3, 4.1) |
| Composite Inflammation Scorec | −3.4 (−6.0, −0.8) | −5.0 (−7.9, −2.1) | 1.6 (−2.4, 5.6) | |
| Knee extension strength (kg) | IL-6 (pg/ ml) | 71.6 (64.8, 78.4) | 75.5 (68.7, 82.4) | −3.9 (−13.8, 5.9) |
| Composite Inflammation Scorec | 73.9 (66.7, 81.0) | 78.8 (70.8, 86.8) | −5.0 (−15.9, 5.9) | |
| Hand grip strength (kg) | IL-6 (pg/ ml) | 33.8 (32.6, 35.1) | 33.4 (32.1, 34.6) | 0.5 (−1.3, 2.3) |
| hs-CRP (mg/ L) | 34.0 (32.6, 35.3) | 34.1 (32.7, 35.5) | −0.1 (−2.1, 1.8) | |
| Composite Inflammation Scorec | 34.1 (32.8, 35.3) | 34.0 (32.6, 35.5) | 0.01(−1.9, 2.0) | |
| Specific strength | ||||
| Upper extremity specific strength (kg/ kg)d | TNFα (pg/ ml) | 5.8 (5.5, 6.0) | 5.9 (5.7, 6.2) | −0.1 (−0.5, 0.2) |
| hs-CRP (mg/ L) | 5.8 (5.6, −6.1) | 5.8 (5.6, −6.1) | −0.01(−0.4, 0.4) | |
| IL-6 (pg/ ml) | 5.8 (5.6, 6.1) | 5.8 (5.6, 6.1) | −0.01 (−0.4, 0.3) | |
| Composite Inflammation Scorec | 5.8 (5.6, 6.0) | 5.9 (5.6, 6.1) | −0.10 (−0.4, 0.3) | |
| Lower extremity specific strength (kg/ L)e | IL-6 (pg/ ml) | 210.1 (190.1, 230.0) | 229.5 (209.3, 249.6) | −19.4 (−48.1, 9.3) |
| Composite Inflammation Scorec | 214.7 (193.6, 235.7) | 233.5 (209.8, 257.1) | −18.8 (−51.1, 13.5) | |
Note: Only models with a non-linear association between the inflammatory marker and physical function, and analyzed by ANCOVA are shown in this table. Models for physical function and strength were adjusted for race, sex, moderate to vigorous intensity physical activity (MVPA), arm lean mass (hand grip strength) or thigh skeletal muscle (all other physical function scores), and age (gait speed). Models for specific strength were adjusted for race, sex and MVPA. With the exception of the model for gait speed, age was not included as a covariate as it did not improve the models' ability to explain the variance in physical function and was not significantly associated with physical function in these models. For the chair sit and reach test, lower scores indicate a poorer performance; IL-6, interleukin-6; hs-CRP, high sensitivity C-reactive protein; TNFα, tumor necrosis factor-α; a. Inflammatory status determined by median level of inflammatory marker, unless there was a significant inflammatory marker group by covariate interaction. IL-6: Low IL-6 ≤ 2.1 pg/ ml, High IL-6 < 2.1 pg/ ml; hs-CRP: Low hs-CRP ≤ 2.7 mg/L, High hs-CRP > 2.7 mg/L; TNFα: Low TNFα ≤ 4.7pg/ml, High TNFα > 4.7pg/ml; b. Non-linear association between hs-CRP and six minute walk test. Hs-CRP status delineated by point of inflection on curve: Low hs-CRP ≤ 1.8 mg/L, High hs-CRP > 1.8 mg/L; c. The composite inflammation score was computed by combining the 3 inflammatory markers. High overall inflammation status defined as having ≥ two inflammatory markers above the median (IL-6 < 2.1 pg/ ml, hs-CRP < 2.7 mg/L and/or TNFα < 4.7pg/ml). Low overall inflammation status defined as having ≤ one inflammatory marker above the median; d. Upper extremity specific strength calculated as the ratio of hand grip strength (kg) to arm lean mass (kg) by dual energy x-ray absorptiometry (DXA); e. Lower extremity specific strength calculated as the ratio of isometric knee extension strength (kg) to thigh skeletal muscle mass (L) by magnetic resonance imaging (MRI); * P< 0.01 significantly different by inflammatory status.