Epidemiological characteristics of chronic fatigue syndrome/myalgic encephalomyelitis in Australian patients

Figures & data

Table 1 Summary of symptom criteria for CFS/ME

Symptoms	Fukuda criteria	CCC	ICC
Fatigue	At least 6 months New or definite onset Not due to ongoing exertion Not alleviated by rest Substantial reduction in daily activities Not due to other medical conditions associated with fatigue	At least 6 months New onset Not due to ongoing exertion Substantial reduction in daily activities Not due to other medical conditions associated with fatigue	PENEb (all five required)  Marked, rapid fatigue in response to minimal physical and/or mental activity  Fatigue can be immediate or delayed  Symptoms significantly worsen after minimal physical and/or mental activity  Prolonged recovery period  Substantial reduction of daily activities
Additionala	At least four of the following:  Postexertional malaise lasting more than 24 hours  Unrefreshing sleep  Short-term memory and/or concentration difficulties  Muscle pain  Joint pain without swelling/redness  Headaches of new type  Tender lymph nodes  Sore throat	Postexertional malaise and/or fatigue Sleep dysfunction Pain Neurological/cognitive (two or more symptoms) At least one symptom from two of the following subcategories  Autonomic   Orthostatic intolerance   Irritable bowel syndrome   Urinary frequency and bladder dysfunction   Palpitations   Exertional dyspnea  Neuroendocrine manifestations   Loss of thermostatic stability   Subnormal body temperature and marked diurnal fluctuation   Sweating episodes   Feverishness and cold extremities   Intolerance of extremes of temperature   Marked weight change  Immune   Tender lymph nodes   Sore throat   Flu-like symptoms   General malaise   Sensitivities to food, medications, and/or chemicals	Neurological (at least one symptom from the four subcategories):  Cognitive difficulties  Pain  Sleep disturbances  Sensory, perceptual, and motor disturbances Immune, gastrointestinal, and genitourinary (at least one symptom from five subcategories):  Flu-like symptoms  Susceptibility to viral infections  Gastrointestinal tract disturbances  Genitourinary disturbances  Sensitivities to food, medications, odors, and/or chemicals Energy production/transportation impairments (at least one symptom from any subcategory):  Cardiovascular  Respiratory  Loss of thermostatic stability  Intolerance of extremes of temperature

Notes:

a Symptoms accompanying fatigue should not have preceded onset of fatigue and be persistent or recurring.

b Fatigue described as PENE.

Abbreviations: CCC, Canadian Consensus Criteria; CFS/ME, chronic fatigue syndrome/myalgic encephalomyelitis; ICC, International Consensus Criteria; PENE, postexertional neuroimmune exhaustion.

Figure 1 Flowchart for case ascertainment.

Figure 2 Frequency of participants in the CFS/ME registry by state.

Note: Figures correspond to the distribution of participants per state (distribution of the Australian population per state).
Abbreviations: ACT, Australian Capital Territory; CFS/ME, chronic fatigue syndrome/myalgic encephalomyelitis; NT, Northern Territory; NSW, New South Wales; QLD, Queensland; TAS, Tasmania; VIC, Victoria; SA, South Australia; WA, Western Australia.

Table 2 Sample demographic characteristics

Descriptive	Fukuda	ICCa	CFb	Noncases	Total
N (%)	162 (30.3)	171 (32.0)	78 (14.6)	124 (23.2)	535 (100)
Age, mean (SD) (years)	46.7 (11.8)	44.0 (11.7)	48.5 (14.6)	48.6 (11.2)	46.4 (12.0)
Female, n (%)	117 (72.2)	132 (77.2)	62 (79.5)	108 (87.1)	419 (78.6)
BMI (kg/m^2)
Underweight <18.5	9 (5.6)	11 (6.4)	11 (14.1)	4 (3.2)	35 (6.5)
Normal 18.5–24.9	78 (48.2)	86 (50.3)	28 (35.9)	62 (50.0)	254 (47.5)
Overweight 25.0–29.9	62 (38.3)	37 (21.6)	22 (28.2)	28 (22.6)	149 (27.9)
Obese ≥30.0	13 (8.0)	37 (21.6)	17 (21.8)	30 (24.2)	97 (18.1)
Ethnicity, n (%)c
Nonindigenous Australian	125 (77.2)	122 (71.4)	60 (76.9)	91 (73.4)	398 (74.4)
Indigenous Australian	1 (0.6)	2 (1.8)	1 (1.3)	4 (3.2)	8 (1.5)
Oceanian	4 (2.5)	10 (5.9)	0 (0.0)	6 (4.8)	20 (3.7)
NW European	33 (20.4)	49 (28.7)	13 (16.7)	36 (29.0)	131 (24.5)
SE European	8 (4.9)	4 (2.3)	3 (3.9)	6 (4.8)	21 (3.9)
NA and ME	1 (0.6)	1 (0.6)	0 (0.0)	0 (0.0)	2 (0.4)
SE Asian	1 (0.6)	0 (0.0)	0 (0.0)	1 (0.8)	2 (0.4)
SC Asian	1 (0.6)	1 (0.6)	0 (0.0)	1 (0.8)	3 (0.6)
Americans	1 (0.6)	0 (0.0)	0 (0.0)	0 (0.0)	1 (0.2)
Sub-Saharan African	2 (1.2)	1 (0.6)	1 (1.3)	1 (0.8)	5 (0.9)
Education, n (%)
Primary school	1 (0.6)	1 (0.6)	0 (0.0)	0 (0.0)	2 (3.7)
High school	40 (24.7)	42 (24.6)	8 (10.6)	23 (18.6)	113 (21.1)
Professionald	34 (21.0)	40 (23.4)	15 (19.2)	33 (26.6)	122 (22.8)
Undergraduate	49 (30.3)	53 (31.0)	38 (48.9)	43 (34.7)	183 (34.2)
Postgraduate	38 (23.5)	35 (20.5)	17 (21.3)	25 (20.2)	115 (21.5)
Employment, n (%)
Full time	20 (12.4)	17 (9.8)	6 (7.7)	9 (7.3)	52 (9.7)
Part time	45 (27.8)	48 (28.0)	11 (14.1)	22 (17.7)	126 (23.6)
Disabilitye	49 (30.3)	59 (34.7)	31 (39.7)	44 (35.5)	183 (34.2)
Retired	3 (1.9)	4 (2.1)	15 (19.2)	9 (7.3)	31 (5.8)
Unemployed	45 (27.8)	43 (25.4)	15 (19.3)	40 (32.3)	143 (26.7)

Notes:

a ICC group met both Fukuda and ICC criteria.

b CF only.

c Percentage exceeds 100 as participants may be more than one ethnicity: NW, SE, NA, ME, and SC.

d Professional training denotes no university qualification.

e Recipient of a disability pension

Abbreviations: BMI, body mass index; CF, chronic fatigue; ICC, International Consensus Criteria; ME, Middle Eastern; NA, North African; NW, North West; SC, South or Central; SD, standard deviation; SE, South East.

Table 3 Sample onset characteristics for CFS/ME and CF cases

Descriptive	Fukuda	ICCa	CFb
Age of onset (years), mean (SD)	30.8 (12.6)	28.3 (11.4)	35.2 (13.1)
Age of diagnosis (years), mean (SD)	34.7 (12.0)	32.8 (10.9)	38.2 (10.7)
Duration of illness (years), mean (SD)	14.5 (10.1)	14.7 (11.5)	14.0 (11.2)
Onset period, n (%)
Sudden	96 (59.3)	111 (64.9)	62 (79.5)
Gradual	66 (40.7)	60 (35.1)	16 (20.5)
Onset within Australia, n (%)
Queensland	67 (41.4)	57 (33.3)	19 (24.4)
New South Wales	41 (25.3)	41 (24.0)	17 (21.8)
Victoria	23 (14.2)	32 (18.7)	19 (24.4)
South Australia	7 (4.3)	8 (4.7)	14 (18.0)
Western Australia	7 (4.3)	5 (2.9)	2 (2.6)
Northern Territory	2 (1.2)	0 (0.0)	0 (0.0)
Tasmania	0 (0.0)	4 (2.3)	0 (0.0)
Australian Capital Territory	2 (1.2)	7 (4.1)	2 (2.6)
Total	151 (93.2)	154 (90.1)	74 (94.9)
Overseas onset, n (%)
Total	11 (6.8)	17 (9.9)	4 (5.1)
Infectious triggers, n (%)
Respiratory infection	65 (40.1)	72 (42.1)	15 (19.2)
Immunization	14 (8.6)	19 (11.1)	3 (3.9)
Gastrointestinal illness	25 (15.4)	49 (28.7)	11 (14.1)
Dental infection	7 (4.3)	5 (2.9)	1 (1.3)
Urinary tract infection	3 (1.9)	8 (4.7)	1 (1.3)
Blood transfusion	0 (0.0)	1 (0.6)	0 (0.0)
Unfamiliar sickness when traveling	11 (6.8)	19 (11.1)	5 (6.4)
Contaminated water	3 (1.9)	0 (0.0)	0 (0.0)
Poor recycled air	10 (6.2)	6 (3.5)	4 (5.1)
Noninfectious triggers,c n (%)
Toxic chemicals	17 (10.5)	21 (12.3)	6 (7.7)
Heavy metals	6 (3.7)	8 (4.7)	1 (1.3)
Molds	10 (6.2)	16 (9.4)	0 (0.0)
Severe physical trauma	22 (13.6)	21 (12.3)	2 (2.6)
Anesthetic	12 (7.4)	17 (9.9)	1 (1.3)
Undue stress	78 (48.2)	79 (46.2)	16 (20.5)
Steroidd	0 (0.0)	5 (2.9)	0 (0.0)

Notes:

a ICC group met both Fukuda and ICC criteria.

b CF only.

c Percentage does not add to 100 with participants reporting more than one trigger.

d Prescription due to acute respiratory illness.

Abbreviations: CFS/ME, chronic fatigue syndrome/myalgic encephalomyelitis; CF, chronic fatigue; ICC, International Consensus Criteria; SD, standard deviation.

Table 4 Frequency of reported symptoms for CFS/ME and CF cases

Symptom	Fukuda	ICC^a	CF^b	Fukuda vs ICC^c OR (95% CI)
Fatigue, n (%)
Fatigue^d	162 (100.0)	171 (100.0)	78 (100.0)	0 (0.0)
Postexertional malaise	68 (38.9)	171 (100.0)	3 (3.9)	0 (0.0)
PENE^e	25 (15.4)	171 (100.0)	3 (3.9)	0 (0.0)
Cognition, n (%)
Confusion	52 (32.1)	69 (40.4)	1 (1.3)	1.9 (1.2–3)
Disorientation	40 (24.7)	77 (45.0)	1 (1.3)	2.7 (1.7–4.2)
Difficulty processing information	51 (31.5)	65 (38.0)	3 (3.9)	2.4 (1.4–4.4)
Difficulty making decisions	53 (32.7)	66 (38.6)	2 (2.6)	1.7 (1–3)
Slowed speech	46 (28.4)	75 (43.9)	3 (3.9)	2.9 (1.3–3.1)
Difficulty reading	44 (27.2)	78 (45.6)	0 (0.0)	1.9 (1.2–3.2)
Poor short-term memory	54 (33.3)	63 (36.8)	2 (2.6)	1.3 (0.8–2.2)
Pain, n (%)
Headaches	51 (31.5)	64 (37.4)	1 (1.3)	1.9 (1.1–3.2)
Muscle pain	53 (32.7)	65 (38.0)	1 (1.3)	2.7 (1.3–5.6)
Joint pain	54 (33.3)	62 (36.3)	0 (0.0)	1.1 (0.7–1.8)
Abdomen pain	42 (25.9)	71 (41.5)	2 (2.6)	2.4 (1.5–3.7)
Chest pain	48 (29.6)	73 (42.7)	1 (1.3)	1.7 (1.1–2.7)
Sleep disturbances, n (%)
Insomnia	46 (28.4)	69 (40.4)	2 (2.6)	2.1 (1.4–3.3)
Prolonged sleep	51 (31.5)	57 (33.3)	3 (3.9)	1.1 (0.7–1.6)
Reversed sleep	25 (15.4)	84 (49.1)	2 (2.6)	3.8 (2–7.4)
Frequent awakenings	47 (29.1)	71 (41.5)	2 (2.6)	2.1 (1.4–3.3)
Awakening earlier than expected	43 (26.5)	72 (42.1)	3 (3.9)	2 (1.3–3.1)
Vivid dreams or nightmares	42 (25.9)	75 (43.9)	2 (2.6)	2.6 (1.7–4)
Unrefreshed sleep	54 (33.3)	63 (36.8)	3 (3.9)	2.2 (0.9–5.3)
Sensory, perceptual, and motor disturbances, n (%)
Inability to focus vision	47 (29.0)	69 (40.4)	1 (1.3)	1.9 (1.3–3)
Sensitivitiesf	50 (30.9)	68 (39.8)	3 (3.9)	3.9 (2.0–7.4)
Poor depth perception	30 (18.5)	78 (45.6)	1 (1.3)	3.1 (1.8–5.2)
Muscle weakness	52 (32.1)	65 (38.0)	2 (2.6)	2.1 (1.2–3.7)
Twitching	49 (30.3)	70 (40.9)	2 (2.6)	1.7 (1.1–2.5)
Poor coordination	49 (30.3)	67 (39.2)	2 (2.6)	1.6 (1.0–2.5)
Feeling unsteady on feet	44 (27.2)	70 (40.9)	2 (2.6)	2.8 (1.7–4.4)
Immune (infectious), n (%)
Sore throat	45 (27.8)	73 (42.7)	1 (1.3)	2.4 (1.6–3.8)
Tender lymph nodes	46 (28.4)	75 (43.9)	0 (0.0)	2.2 (1.4–3.4)
Sinusitis	46 (28.4)	69 (40.4)	1 (1.3)	1.7 (1.1–2.7)
Recurrent or persistent infections	46 (28.4)	71 (41.5)	1 (1.3)	1.6 (1.0–2.6)
Gastrointestinal and genitourinary, n (%)
Nausea	44 (27.2)	73 (42.7)	1 (1.3)	2.4 (1.5–3.7)
Abdominal pain	42 (25.9)	76 (44.4)	2 (2.6)	2.7 (1.7–4.2)
Bloating	50 (30.9)	66 (38.6)	1 (1.3)	1.7 (1.1–2.7)
Irritable bowelg	46 (28.4)	65 (38.0)	2 (2.6)	1.8 (1.1–2.7)
Intolerancesh	45 (27.8)	68 (39.8)	3 (3.9)	3.6 (2.2–6)
Urinary urgency or frequency	44 (27.2)	68 (39.8)	2 (2.6)	2.2 (1.4–3.5)
Cardiovascular, n (%)
Orthostatic intolerancy	46 (28.4)	93 (54.4)	1 (1.3)	2.8 (1.8–4.3)
Ataxiai	26 (16.1)	90 (52.6)	4 (5.1)	3.3 (0.9–12.3)
Heart palpitations	42 (25.9)	65 (38.0)	2 (2.6)	2 (1.3–3.1)
Light headedness	48 (29.6)	70 (40.9)	2 (2.6)	3.5 (2.0–6.1)
Respiratory, n (%)
Air hunger	44 (27.2)	64 (37.4)	3 (3.9)	1.6 (1.0–2.4)
Labored breathing	42 (25.9)	67 (39.2)	1 (1.3)	1.8 (1.1–2.8)
Fatigue of chest muscles	50 (30.9)	68 (39.8)	2 (2.6)	1.4 (0.9–2.2)
Autonomic, n (%)
Abnormal body temperature	41 (25.3)	66 (38.6)	1 (1.3)	2 (1.3–3.1)
Fluctuating body temperature	48 (29.6)	67 (39.2)	1 (1.3)	1.5 (1.0–2.3)
Sweating episodes	45 (27.8)	67 (39.2)	1 (1.3)	1.9 (1.2–2.9)
Recurrent feverishness	43 (26.5)	75 (43.9)	0 (0.0)	2.1 (1.4–3.3)
Cold extremities	45 (27.8)	72 (42.1)	2 (2.6)	2.6 (1.7–4.2)
Intolerance of extremes temperature	50 (30.7)	67 (39.2)	2 (2.6)	2.3 (1.4–4)

Notes:

a ICC group met both Fukuda and ICC criteria.

b CF only.

c OR, 95% CI.

d Fatigue not due to ongoing exertion and significantly interferes with daily activities and work for at least 6 months.

e PENE defined as the following symptoms after minimal activity: 1) marked postexertional fatigue, 2) postexertional symptom exacerbation, 3) onset of fatigue can be immediate or delayed, 4) prolonged recovery period of usually 24 hours of longer, and 5) lack of stamina (substantial reduction in premorbid activities).

F Sensitivity to light, noise, vibration, odor, taste, and/or touch.

g Irritable bowel described as abdominal pain, bloating, and alternating constipation and diarrhea.

h Intolerance to food, medications, odors, or chemicals.

i Self-reported diagnosis.

Abbreviations: CFS/ME, chronic fatigue syndrome/myalgic encephalomyelitis; CF, chronic fatigue; CI, confidence interval; ICC, International Consensus Criteria; OR, odds ratio; PENE, postexertional neuroimmune exhaustion.