Table 2. Primary outcomes.
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| Observed unadjusted mean (SD) | Slope (95% CI) | Adjusted Mean difference (95% CI) | ||||||||
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| Oregon | Minnesota | SMT 0 | SMT 6 | SMT 12 | SMT 18 | Per 6 SMT sessions | SMT 0 vs SMT 6 | SMT 0 vs SMT 12 | SMT 0 vs SMT 18 | |
| Days with CGH (last 4 wk) | ||||||||||
| 0 wk | 15.8 (6.7) | 15.3 (6.6) | 15.1 (6.3) | 15.2 (7.2) | 16.2 (6.9) | 15.8 (6.1) | ||||
| 6 wk | 12.3 (8.0) | 11.0 (7.9) | 12.5 (8.2) | 12.2 (8.2) | 11.2 (7.5) | 10.6 (8.0) | -0.8 (-1.5, -0.2)* | -0.2 (-2.1, 1.7) | -1.8 (-3.7, 0.2) | -2.3 (-4.2, -0.3)* |
| 12 wk | 10.6 (8.0) | 9.8 (8.2) | 11.2 (7.9) | 11.2 (8.4) | 10.3 (8.7) | 8.1 (7.4) | -1.1 (-1.9, -0.4)* | -0.3 (-2.5, 1.9) | -1.9 (-4.1, 0.4) | -3.3 (-5.6, -1.0)* |
| 24 wk | 10.4 (8.5) | 9.2 (8.0) | 10.8 (8.1) | 10.0 (8.2) | 9.7 (8.7) | 8.6 (8.0) | -1.0 (-1.7, -0.2)* | -0.5 (-2.8, 1.8) | -1.7 (-4.1, 0.6) | -2.9 (-5.2, -0.5)* |
| 39 wk | 9.4 (8.1) | 8.9 (8.1) | 10.2 (8.1) | 9.3 (8.5) | 8.9 (8.1) | 8.2 (7.8) | -0.9 (-1.7, -0.1)* | -0.6 (-3.1, 1.8) | -1.8 (-4.3, 0.6) | -2.6 (-5.1, -0.1)* |
| 52 wk | 9.6 (8.6) | 9.5 (8.4) | 10.6 (8.5) | 10.1 (9.1) | 9.6 (8.7) | 8.2 (7.5) | -1.1 (-1.9, -0.3)* | -0.2 (-2.6, 2.2) | -1.7 (-4.1, 0.7) | -3.2 (-5.6, -0.7)* |
| 6 to 52 wk† | -1.0 (-1.6, -0.4)* | -0.4 (-2.3, 1.6) | -1.8 (-3.8, 0.2) | -2.8 (-4.9, -0.8)* | ||||||
SD, standard deviation; CI, confidence interval; UWS, University of Western States; NWHSU, Northwestern Health Sciences University; SMT, spinal manipulation; CGH, cervicogenic headache.
Primary endpoints were prespecified as days with CGH in the prior 4 weeks evaluated at the 12 and 24-week follow-up. Unadjusted means are from original data without imputation; slopes and mean differences are computed from imputed data and adjusted for baseline covariates.
Negative signs of slopes and risk differences favor higher doses of manipulation.
*
p<.05.
†
Longitudinal profile using generalized estimating equations.