The impact of symptom stability on time frame and recall reliability in CFS

Figures & data

Table 1. Means and standard deviations of symptom composites on the SI-R at interviews 1 and 2 for symptoms rated as variable

Variable symptoms	Time frame	Interview 1	Interview 2
		M (SD)	M (SD)
Sore throats		n = 30	n = 30
	Week	4.30 (4.20)	4.80 (5.01)
	Month	4.10 (3.43)	4.33 (4.44)
	Six months	5.10 (4.20)	5.40 (5.75)
Lymph nodes		n = 23	n = 23
	Week	5.83 (4.56)	4.70 (4.26)
	Month	5.43 (4.83)	5.04 (4.83)
	Six months	6.17 (4.52)	5.22 (3.43)
PEM		n = 5	n = 5
	Week	12.00 (2.12)	13.60 (5.55)
	Month	14.00 (6.36)	10.60 (3.71)
	Six months	15.20 (7.79)	13.60 (3.05)
Muscle pain		n = 20	n = 20
	Week	8.75 (4.66)	7.45(3.85)
	Month	7.60 (4.92)	7.85 (3.91)
	Six months	8.50 (4.76)	7.75 (4.04)
Joint pain		n = 23	n = 23
	Week	7.30 (5.45)	7.26 (5.15)
	Month	7.26 (5.15)	7.61 (5.79)
	Six months	7.78 (5.66)	7.22 (4.60)
Unrefreshing sleep		n = 10	n = 10
	Week	10.10 (5.92)	11.30 (6.53)
	Month	9.70 (4.72)	10.00 (5.29)
	Six months	7.50 (4.79)	7.70 (3.86)
Headache		n = 31	n = 31
	Week	6.19 (5.21)	6.68 (5.75)
	Month	6.74 (5.11)	5.65 (4.05)
	Six months	7.19 (5.94)	6.45 (3.80)
Memory		n = 19	n = 19
	Week	7.16 (5.27)	7.63 (7.27)
	Month	6.5 (5.2)	7.32 (5.31)
	Six months	7.95 (6.51)	7.37 (4.78)
Concentration		n = 16	n = 16
	Week	10.69 (5.92)	10.06 (5.73)
	Month	10.13 (5.71)	9.81 (4.07)
	Six months	9.81 (4.07)	10.75 (5.36)

Table 2. Means and standard deviations of symptom composites on the SI-R at interviews 1 and 2 for symptoms rated as stable

Stable symptoms	Time frame	Interview 1	Interview 2
		M (SD)	M (SD)
Sore throats		n = 8	n = 8
	Week	10.88 (5.00)	12.38 (7.73)
	Month	11.63 (5.45)	9.75 (5.83)
	Six months	14.38 (7.01)	12.50 (4.41)
Lymph nodes		n = 14	n = 14
	Week	11.14 (6.24)	10.57 (6.72)
	Month	11.14 (6.41)	8.86 (6.01)
	Six months	13.14 (7.43)	11.21 (6.42)
PEM		n = 46	n = 46
	Week	17.35 (4.87)	17.22 (4.65)
	Month	17.33 (4.76)	17.17 (4.65)
	Six months	18.20 (5.45)	17.52 (5.15)
Muscle pain		n = 30	n = 30
	Week	14.57 (5.86)	13.73(5.39)
	Month	14.87 (6.27)	14.03 (5.76)
	Six months	15.03 (6.20)	14.10 (5.54)
Joint pain		n = 22	n = 22
	Week	13.09 (5.89)	13.72 (6.23)
	Month	13.95 (6.03)	12.91 (5.65)
	Six months	14.18 (7.20)	13.73 (5.96)
Sleep		n = 41	n = 41
	Week	18.59 (4.76)	18.90 (5.39)
	Month	17.85 (5.58)	17.24 (5.26)
	Six months	18.32 (6.12)	17.95 (5.55)
Headache		n = 16	n = 16
	Week	11.56 (7.20)	9.94 (6.69)
	Month	10.44 (4.41)	10.50 (6.48)
	Six months	12.88 (5.49)	11.00 (6.21)
Memory		n = 31	n = 31
	Week	12.77 (6.28)	11.94 (6.58)
	Month	13.16 (5.75)	12.35 (6.45)
	Six months	12.94 (6.21)	13.13 (7.05)
Concentration		n = 35	n = 35
	Week	12.23 (5.88)	12.83 (7.08)
	Month	12.66 (6.32)	12.77 (6.88)
	Six months	13.60 (6.57)	13.17 (6.97)

Table 3. Slope coefficients of variable CFS symptoms at three time frames

Variable symptoms	Time frame	b	SE	df	t	p
Sore throat	Week	.20	.17	61.99	1.19	.239
	Month	−.04	.31	58.68	−.14	.888
	Six months^*	.80	.17	62.39	4.81	<.001
Lymph node pain	Week	.03	.29	47.25	.12	.91
	Month	.07	.33	46.08	.22	.824
	Six months^*	.77	.28	47.43	2.71	.009
PEM	Week	−.29	.47	6.84	−.62	.557
	Month^*	.44	.63	6.35	.706	.505
	Six months	.31	.45	6.93	.68	.518
Muscle pain	Week	−.23	.24	4.54	−.98	.335
	Month	−.22	.36	38.12	−.60	.553
	Six months^*	.56	.25	40.21	2.25	.03
Joint pain	Week^*	.58	.29	47.81	2.00	.051
	Month	.15	.33	47.35	.45	.655
	Six months	.22	.21	49.54	1.04	.304
Unrefreshing sleep	Week	.64	.48	18.35	1.33	.199
	Month^*	.82	.67	17.22	1.22	.238
	Six months	.30	.56	17.71	.54	.598
Headaches	Week	−.08	.22	76.77	−.37	.711
	Month	−.51	.36	69.80	−1.42	.159
	Six months^*	.32	.24	74.54	1.30	.197
Memory	Week	−.14	.34	38.47	−.41	.688
	Month^*	−.07	.45	37.23	−.15	.881
	Six months	−.14	.29	39.71	−.50	.62
Concentration	Week	.04	.27	39.80	.27	.786
	Month	−.17	.37	36.39	−.45	.654
	Six months^*	.20	.43	35.81	.46	.647

^* Optimal time frame (coefficients closest to 1.0).

Table 4. Slope coefficients of stable CFS symptoms at three time frames

Stable symptoms	Time frame	b	SE	df	t	p
Sore throat	Week	−.97	.85	16.25	−1.15	.268
	Month	1.84	1.34	15.13	1.38	.188
	Six months^*	.18	.76	16.67	.23	.819
Lymph node pain	Week	.12	.60	29.83	1.29	.847
	Month	.30	.86	26.62	.347	.731
	Six months^*	1.30	.49	28.53	2.63	.014
PEM	Week	.44	.21	104.93	2.13	.04
	Month	.30	.23	102.45	1.31	.195
	Six months^*	.79	.19	106.85	4.09	<.001
Muscle pain	Week	−.56	.40	74.44	−1.41	.164
	Month	.75	.55	69.15	1.35	.182
	Six months^*	.82	.44	72.40	1.86	.067
Joint pain	Week	−.64	.37	46.25	−1.74	.089
	Month	1.82	.53	43.62	3.43	.001
	Six months^*	.95	.35	46.75	2.72	.009
Unrefreshing sleep	Week	.18	.26	89.80	.67	.504
	Month	.29	.23	91.14	1.24	.218
	Six months^*	.41	.17	95.17	2.34	.021
Headaches	Week	.00	.24	30.17	.012	.991
	Month	.30	.48	27.75	.62	.543
	Six months^*	1.40	.23	30.36	6.04	<.001
Memory	Week	−.17	.21	60.32	−8.26	.412
	Month	.04	.29	59.13	.14	.893
	Six months^*	1.03	.19	60.72	5.32	<.001
Concentration	Week	−.43	.31	71.52	−1.41	.164
	Month	.14	.30	71.73	.48	.634
	Six months^*	.47	.23	74.15	2.07	.042

^* Optimal time frame (coefficients closest to 1.0).