TABLE 1.

Association between fatigability, fatigue, activity, and clinical and demographic characteristics^aa

	Fatigability						Fatigue						Activity
	Pittsburgh Fatigability Scale			Situational Fatigue Scale~			FACIT Fatigue			PROMIS Fatigue			PROMIS-PF Ambulatory			PROMIS-PF Non-ambulatory
	Coef.*	95% Cl	P	Coef.*	95% Cl	P	Coef.*	95% Cl	P	Coef.*	95% Cl	P	Coef.*	95% Cl	P	Coef.*	95% Cl	P
Age (years)
18–44	Referent			Referent			Referent			Referent			Referent			Referent
45–59	2.0	0.66–3.3	<.01	2.1	1.2–3.1	<.01	0.68	−1.5 – 2.9	.54	0.21	−1.5 – 2.0	.82	−2.6	−4.5 – −0.63	.01	−3.3	−7.2 – 0.48	.09
60–74	2.3	1.0–3.7	<.01	2.2	1.3–3.1	<.01	−0.83	−3.1 – 1.4	.47	0.09	−1.6 – 1.7	.92	−3.8	−5.7 – −1.9	<.O1	−3.3	−7.0 – 0.42	.08
≥75	3.2	1.7–4.8	<.01	2.8	1.7–3.8	<.01	1.2	−3.7 – 1.4	.37	−3.1	−5.0 – −1.1	.02	−4.7	−7.1 – −2.4	<.O1	−5.1	−8.9 – −1.2	.01
# of Comorbidities
0	Referent			Referent			Referent			Referent			Referent			Referent
1–2	1.7	0.26–3.1	.02	1.2	0.16–2.2	.02	−0.67	−1.7 – 3.0	.58	0.68	−1.2 – 2.5	.47	−1.5	−3.6 – 0.56	.15	−1.1	−5.2 – 3.0	.61
3–4	2.8	1.2–4.4	<.01	1.5	0.34–2.6	.01	−1.1	−1.6 – 3.9	.41	0.85	−1.2 – 2.9	.41	−3.6	−5.9 – −1.22	<.O1	−0.63	−4.8 – 3.6	.77
≥5	3.5	2.0–5.0	<.01	1.2	0.16–2.2	.02	−2.9	−0.35 – 5.4	.03	1.5	−0.41 – 3.4	.13	−4.2	−6.4 – −2.1	<.O1	−0.41	−4.4 – 3.6	.84
Hemoglobin (g/dL)
9 ≤ Hb < 10	Referent			Referent			Referent			Referent			Referent			Referent
8 ≤ Hb < 9	0.6	−0.59 – 1.9	.31	0.22	−0.65 – 1.1	.63	2.3	0.23–4.3	.03	−0.36	−1.9 – 1.2	.66	−0.50	−2.3 – 1.3	.59	−4.2	−7.2 – −1.1	.08
7 ≤ Hb < 8	1.4	0.07–2.7	.04	0.57	−0.32 – 1.5	.21	2.7	0.49–4.9	.02	0.52	−1.1 – 2.2	.53	0.67	−1.2 – 2.5	.48	−2.2	−5.6 – 1.2	.21
Hb < 7	1.7	0.41–2.9	.01	0.84	−0.01 – 1.7	.05	2.4	0.23–4.5	.03	0.4	−1.2 – 2.0	.62	−0.48	−2.4 – 1.4	.61	−3.5	−6.4 – −0.58	.02

Note: Situational Fatigue Scale Physical Fatigue Subscale, which includes questions that ask about fatigue in the context of activity (ie, fatigability).

Abbreviations: FACIT Fatigue = Functional Assessment of Chronic Illness Therapy Fatigue Subscale score range 0–52; PROMIS Fatigue = Patient Reported Outcome Measurement Instrument System-Fatigue Short Form 8a score range 8–40; PROMIS-PF Ambulatory = Patient Reported Outcome Measurement Instrument System Physical Function with Mobility Aid (patients able to walk 25 ft) score range 11–55; PROMIS-PF Non-Ambulatory = Patient Reported Outcome Measurement Instrument System Physical Function with Mobility Aid (patients NOT able to walk 25 ft) score range 8–40.

^aModel Controls for: gender, race, SCD, GIBL, and depression.