Table 4.

Interaction model to test temporal trend differences among studies (n=316) ^a

Variable	Beta Estimate	Standard Error	95% Confidence Interval
Time of data collection
Baseline (intercept)***	71.26	4.10	63.23, 79.29
3 Months*	−2.36	1.19	−4.69, −0.03
6 Months**	−4.64	1.54	−7.66, −1.61
Total Number of Symptoms***	−1.46	0.10	−1.65, −1.27
Age***	−0.20	0.05	−0.30, −0.09
Study
Study 1 (reference)
Study 2*	−3.38	1.52	−6.36, −0.39
Study 3***	−11.26	1.19	−13.58, −8.93
Study 4	−0.75	1.82	−4.33, 2.82
Study 5***	−9.82	1.49	−12.74, −6.89
Study × time of data collection
Study 2 × 3 Months**	4.65	1.73	1.25, 8.05
Study 2 × 6 Months***	11.70	2.17	7.44, 15.95
Study 3 × 3 Months***	13.50	1.33	10.89, 16.12
Study 3 × 6 Months***	17.68	1.71	14.32, 21.04
Study 4 × 3 Months	−2.40	2.12	−6.55, 1.74
Study 4 × 6 Months	0.46	2.74	−4.91, 5.84
Study 5 × 3 Months***	11.57	1.67	8.31, 14.84
Study 5 × 6 Months***	15.28	2.11	11.15, 19.41

^aJoint Wald test for interaction terms: p <0.0001.

^*p<0.05;

^**p<0.01;

^***p<0.001