Table 2.
Work-related outcomes and naturally occurring improvement rate.
| Study | Criteria | n | Mean Age in Years | Illness Duration at Baseline | Length of follow-up (FU) | Works Status | Rate of Improvement |
|---|---|---|---|---|---|---|---|
| Andersen et al. (2007) [33] | Meeting both CDC 1988 and Fukuda | 34 | 46.4 at diagnosis | 4 yrs | 9 yr | 76.5% (26/34) medically retired; 1 worked full time in physically less demanding job, 2 worked part-time, 3 were freelance + on disability payments | As a group patients had not improved; 6% recovered & 10% had received other diagnosis |
| Assefi et al. (2011) [63] | Fukuda | 555 (fatigue study, 207 CFS patients) | 38.2 | 4.4 yr | No FU | Of the CFS patients, 61% worked, 44% worked less hours, 29% lost jobs due to illness, 30% received illness benefits; 23% changed jobs due to illness, 30% took significant pay cut | No FU |
| Behan et al. (1985) [64] | Unclear | 50 | 37 | 5 yrs | No FU | 4 of the 5 doctors and all 8 nurses were unable to continue work; the medical student withdrew from his course for a yr. No employment data provided for the other 37 patients | The illness was chronic in 37 patients but had a relapsing and remitting course in 13. |
| Bombardier and Buchwald (1995) [38] | CDC 1988 | 498 (fatigue study, 226 CFS patients) | 38.1 | 5.2 yrs | 1.5 yrs | CFS patients at FU: 40% unable to work at all, 20% unable to work full-time, 22% decreased work performance, 16% increased work performance, 11% resuming full time and 13% part-time work. | 2% recovered, 24% had worsened, 12% were unchanged, rest improved slightly to significantly. |
| Brown et al. (2012) [65] | Bell and Bell 1988 | 35 (25 CFS + 10 healthy controls HC) | 37 | 25 yrs | 25 yr follow-up of patients who fell ill as adolescents; average age at illness onset 12.1 yrs [66] | Full-time employment: 90% HC, 71.4% CFS. CFS: working part time 11.4% and 16.4% on disability |
80% remitted yet still showed more impairment on 21 of 23 outcomes compared to healthy controls and on 17 of 23 outcomes there was no difference with those who maintained a CFS diagnosis |
| Buchwald et al. (1996) [67] | 1998 CDC | 431 (fatigue clinic patients including 185 CFS) + 99 HC | 39 | 4.7 yrs | No FU | Employed: CFS 46% (part-time and full time) vs. 91% HC | No FU |
| Castro-Marrero et al. (2017) [3] | Meeting both Fukuda and Canadian criteria | 1757 | 47.7 | 10 yrs | No FU | 62.8% unemployed, 25.6% employed, 11.6% never worked | No FU |
| Chu et al. (2019) [68] | Fukuda | 200, no controls | 53.7 | Unclear | 2 yrs | At baseline, 47% permanently disabled; 15% worked >30 h/week | Response rate: 75% (150/200); 4% improved, 96% no improvement |
| Ciccone et al. (2010) [44] | Fukuda | 94 (women only, no controls) | 41.6 | 5.9 yrs | Biannual telephone surveys over a period of 2.5 yrs | Employed: 50.8% improvers, 29.0% nonimprovers. Disabled: 41.3% improvers, 71.0% nonimprovers | Response rate: 63.5% (94/148); 67% improved but were still far short of recovery |
| Clark et al. (1995) [37] | 1988 CDC | 98, no controls; chronic fatigue study, 19 CFS patients | 39.9 | 5.5 yrs | 2.5 yrs | Employment status not mentioned | Response rate: 79.6% (78/98); of the CFS patients 7 (37%) recovered and 12 (63%) did not recover |
| Claypoole et al. (2001) [69] | Fukuda | 29 twin pairs (monozygotic twins and their healthy siblings) | 41.2 | 7.2 yrs | No FU | Employed: 43% CFS, 90% HC | 24% dropped out. |
| Collin et al. (2011) [46] | Fukuda | 2170 | 38.6 women, 41.4 men | 35 mo currently employed, 48 mo employment discontinued | Single measurement, no FU | 40.7% were employed, 50.1% had discontinued work due to CFS | No FU. Employment status recorded for 1991 patients (91.8%). |
| Garcıa-Borreguero et al. (1998) [70] | Fukuda | 82 (41 CFS and 41 healthy unrelated neighbours) | 37.6 CFS, 38.4 healthy neighbours | 5.5 yrs | No FU | Vocational disability: 17.1% partial, 56.1% full CFS, not applicable in healthy neighbours | No FU |
| Hill et al. (1999) [47] | 1988 CDC | 23 ("severe" subset of CFS patients) | 35 | 2.4 yrs | 3.4 yrs (FU at 1.6 yrs and also at 3.4 yrs) | Employed at baseline: 5 full-time and 1 part time; 2 returned to part-time work at 1st follow-up and 1 of them became disabled again | 4% recovered; majority showed no improvement |
| Huibers et al. (2006) [71] and Leone et al. (2006) [56] | Fukuda | 151 fatigued employees (52 with CFS like cases at baseline) | 43.9 | 35.0 mo CFS like cases (at baseline) | 4 yrs (FU at 1 yr and 4 yrs) | Work disability CFS like cases: 41% baseline, 20% at 12 month FU, 27% at 4 yr FU. At final follow-up, 59.6% were on sick leave, full or partial work incapacity, unemployed or retired |
Response rate: 84% (127/151). 40% went on to meet CFS criteria at follow-up; 16.9% developed a CFS like status during the 4 yrs and 57% still met criteria for severe fatigue. |
| Jason et al. (2008) [72] study 1 | Fukuda | 79 (32 CFS vs. 47 HC) | 37 | Unclear | No FU | Working full time: 33.3% (CFS) vs. 86.7% (HC); Part-time: 19% vs. 6.7% Unable to work due to illness 42.8% vs. 0% |
No FU |
| Jason et al. (2008) [72] study 2 | Fukuda | 114 (no control group) | 42 | Unclear | No FU | Working: 26.4% part-time and 25.3% full-time. 76% had to cut down on their work, 49.4 % were receiving disability or were unemployed due to CFS |
No FU |
| Jason et al. (2011) [41] | Fukuda | 213 (study included 32 with CFS and 47 HC) | 36.8 CFS 41.4 HC | Unclear | 10 yrs | At baseline: on disability 20.8% CFS and 9.1% HC Working part time: 8.3% CFS and 13.6% HC; full-time: 37.5% CFS and 68.2% HC. No employment data provided for follow-up. |
86% of CFS patients followed up. Over time the CFS group remained rather ill |
| Johnston et al. (2016) [28] | CFS diagnosis by their primary physician | 535 (30.3% Fukuda cases; a further 32.0% met both Fukuda and ICC; 23.2% CF; 14.6% received other diagnosis) | 46.4 | 14.5 yrs | No FU | Fukuda: 12.4% working full-time, 27.8% part-time; receiving disability 30.3%, unemployed 27.8%; ICC: 9.8% working full-time, 28.0% part-time, 34.7% receiving disability, 25.4% unemployed |
No FU |
| Levine et al. (1992) [73] | Postviral fatigue syndrome defined on the basis of severe persistent fatigue | 31 patients following one of four outbreaks in USA | Incline Village + Truckee 40.7; Yerington 31.1; Placerville 41.1 | Unclear | 3 yrs | No employment data | Response rate: 90.3% (28/31). At 2 years 46.2% (12/26) functioning without limitation, after 2 years almost all study objects were back to pre-illness activity |
| Lin et al. (2011) [74] | Fukuda | 500 (264 chronic fatigue, 112 CFS, 124 HC) | 35.8 | CFS patients: 53% onset age 25 or later, 15% age 24 or earlier, 32% age unknown | No FU | Working during the last 4 weeks: 71% CFS vs. 95% healthy controls | No FU |
| Lloyd et al. (1994) [75] | Lloyd 1988 | 25 (12 male CFS patients, 13 male HC) | 33.5 | 60 mo | No FU | 41.7% (5/12) were working on a limited part time basis (CFS) vs. 100% HC (full-time); 58.3% (7/12) had stopped working due to CFS | No FU |
| Lowry and Pakenham (2008) [76] | Fukuda | 139 | 48.3 yrs | 11.2 yrs | No FU | 24% in some form of employment, 40% on sick leave or disability benefits, 19% retired, 17% divided equally between the categories of student, unemployed (but able to work), or performing home duties | No FU |
| Matsuda et al. (2009) [77] | Japanese CFS criteria | 155 | 32.7 yrs | 54 mo | 22.5 mo | At baseline: 47% were working; 42% unemployed and 11% student. No employment data for follow-up | Response rate: 45% (70/155); 12% recovered, 85% had a poor outcome. |
| McCrone et al. (2003) [78] | Fukuda | 141 (fatigue study, 44 CFS) | 40 yrs | Unclear | No FU. Service use assessment. | 30% lost employment due to illness | No FU |
| Naess et al. (2012) [79] | Fukuda | 58 (CFS after Giardia enteritis; 38 employees, 20 students) | 38.0 females and 31.7 males | 2.7 yrs | No FU. Assessment 2.7 yrs after falling ill | 34.2% (13/38) Of the employees were working part time, 57.9% (22/38) sick leave, 13.2% (5/38) disability pension. 30% (6/20) of the students studied half time and 70% (14/20) too ill to study. | At the time of assessment 16% (9/58) reported improvement, 28% (16/58) no change, and 57% (33/58) slight or significant worsening. |
| Natelson et al. (1995) [80] | 1988 CDC | 113 (41 CFS, 19 MS, 17 major depression, 36 HC) | 34.4 CFS, 38.3 MS, 41.9 depression, 34.6 HC | Unclear | No FU | Disabled: 56% CFS, 5% MS, 18% depression, 0% HC. CFS patients who could work were unable to do so without limitations | No FU |
| Nijs et al. (2005) [81] | Fukuda | 54 | 39 | 68 mo | No FU | Employment rate 95.0% before CFS; currently 29.4% due to CFS; 50% on disability | No FU |
| Nisenbaum et al. (2003) [34] | Fukuda | 65 | 46 | 13.0 yrs | 91%, 60% and 37% were followed up for 1, 2 and 3 yrs | Employed: 63.1% at baseline, 61.2% at 1 yr, 55.2% at 2 yr and 55.6% at 3 yr FU. Unemployed due to CFS: 16.9% at baseline, 18.4% at 1 yr, 13.8% at 2 yr and 16.7% at 3 yr FU. |
57% had a relapsing remitting course; 23.1% received alternative diagnosis, 10% sustained total remission |
| Nyland et al. (2014) [52] | Fukuda | 111 (CFS after mononucleosis) | Mean age at onset 23.7 | 4.7 yrs at baseline and 11.4 yrs at FU | 6.5 yrs | At the time of falling ill 47% were employed and 52% were students. At baseline 8% worked full time, 1% part-time, 13.5% were students, 75% received full sickness benefits. At follow-up 27% worked full time, 28% part-time and 68.5% (63/92) received full or partial disability benefits. |
Response rate: 83% (92/111). About half of younger patients experienced marked improvement. |
| Pendergrast et al. (2016) [53] | Unclear | 557 (4 groups of CFS patients: from US 216, UK 103 and two from Norway (N1, 175 + N2, 63)); nearly 25% too ill to leave their homes | US 52.0 UK 45.6 N1 43.4 N2 34.9 |
Unclear | No FU | On disability: 56.7% US, 30.2% UK, 84.0% N1, 76.2% N2. Working full or part-time: 13.5% US, 37.5% UK, 9.7% N1, 19% N2 |
No FU |
| Ray et al. (1993) [82] | Oxford | 48 (24 CFS, 24 HC) | 38.3 CFS, 40 HC | 46.6 mo | No FU | Working full-time: 13% (3/24) CFS, 71% (17/24) HC | No FU |
| Roche et al. (2005) [83] | Fukuda | 47 | 46.9 | 10.7 yrs | No FU | Working full-time 14.9%, part-time 14.9%, unemployed 70.2% | No FU |
| Rowe et al. (2019) [84] | Fukuda (PEM, unrefreshing sleep and cognitive symptoms were also required) | 784 (40% started after EBV) | 22.5 yrs (mean age 14.8 at diagnosis) | Illness duration prior to diagnosis: 13.6 mo | 8 yrs (FU on up to 6 occasions, 2 to 16 yrs after diagnosis) | At baseline, 5% not working or studying; 8% less then part time; 24% more than part-time; 63% full-time. In comparison: similarly aged healthy people: 85% worked/studied full-time, 6% able to work but unemployed | Response rate 81.8% (641/784). Reporting recovery: 38% at 5 yrs and 68% at 10 yrs; 58% reported continuous pattern of illness with fluctuating severity; 5% remained very unwell and 20% significantly unwell. |
| Russo et al. (1998) [85] | 1988 CDC | 98 (fatigue study, 27% CFS, increased to 42% at follow-up) | 39.9 | 5.5 yrs | 2.5 yrs | Number of subjects not working at enrolment not given; 29.5% returned to work. Unclear how many of those had CFS | Response rate 80% (78/98); unclear how many had CFS; 3% (2/78) fully recovered and 26% of the sample worse |
| Saltzstein et al. (1998) [86] | Fukuda | 15 female patients | 41.2 | Unclear; 46.7% (7/15) were ill for less than 2 yrs | 2 yrs | All were in full-time employment before CFS, at assessment 40% (6/15) worked full-time, 33% (5/15) part-time and 26.7% (4/15) were unemployed | 20% were worse or the same; 80% were improved of which 20% (3/15) reported recovery |
| Schmaling et al, (1998) [87] | 1988 CDC | 37 (15 CFS, 11 depression, 11 HC); all participants were female | 39.4 CFS, 43.1 depression, 45.6 HC |
Unclear | No FU | Working: 13% CFS, 64% of depression, 91% HC | No FU |
| Schweitzer et al. (1995) [88] | Lloyd 1988 | 77 (47 CFS, 30 HC) | 38 CFS, 29 HC | 5.0 yrs | No FU | CFS unemployed: currently 49%, before CFS 13%; 47% (22/47) retired from employment as a result of CFS. No employment figures for HC | No FU |
| Sharpe et al. (1992) [43] | Minimum of six weeks of fatigue | 177 (fatigue study, 66% had Oxford defined CFS) | 34 yrs | 25 mo | 1 yr | 38% had left or changed their job because of their illness. 73% had days during the past month when they had been entirely unable to work. No baseline data available for comparison | Response rate: 81% (144/177). 13% recovered, 65% were functionally impaired at follow-up and could not walk 100 yards (90 m). |
| Stoothoff et al. (2017) [89] | Unclear | 541 | 46.3 | Unclear | No FU | 62.5% on disability, 17.3% worked full or part time. 14% of those constantly getting worse were still working |
59.7% described their illness as fluctuating, 15.9% as constantly getting worse, 14.1% persisting, 8.5% relapsing and remitting; and 1.9% as constantly getting better. |
| Strickland et al. (2001) [90] | 1988 CDC | 259 (fatigue study after outbreak, 41% had CFS) | 47 CFS | 10 yrs | 10 years after outbreak | No employment data provided | Response rate 47.5% (123/259), 15% of responding CFS patients had recovered |
| Thomas and Smith (2019) [91] | Fukuda | 226 | 41.7 | 62.1 mo | 3 yrs | At baseline 34% in employment, 49% unemployed, 16% on sick leave, 24% retired or home-makers. | Response rate: 57.5% (130/226); 29% reported some improvement at 18 mo and 3 yrs FU. Recovery: 2% at 6 mo, 6% at 18 mo and at 3 yrs. |
| Tiersky et al. (2001) [40] | Fulfilling both the 1988 CDC + Fukuda criteria | 47 | 35.5 | 25.9 mo | 41.9 mo | Employment status did not change; 68% were unable to work due to CFS at baseline and FU; those who worked were only able to perform light duty desk work for 3 to 4 h a day but even this amount of work required rest periods | Response rate: 74.5% (35/47). 57% improved, 43% did not. The majority remained functionally impaired overtime. Overall the prognosis appears to be poor. |
| Tirelli et al. (1994) [92] | 1988 CDC | 265 | 35 | 3 yrs | 24 mo | 38.5% (102/265) stopped working activities for a period ranging from 3 months to 2 years No other employment data provided. | Response rate: 100%; 3% recovered, 8% substantial decrease in symptoms, in 89% symptoms persisted |
| Tritt et al. (2004) [93] | Fukuda | 429 | 41.7 | Unclear | No FU | 37.1% had taken sick leave for more than four weeks in the last 12 months and 56.6% less than 4 weeks; 18.9% (81/429) were on long-term sick leave | No FU |
| Van der Werf et al. (2002) [94] | Fukuda | 79 | 34.8 | 1.4 yrs (minimum illness duration 6 mo, maximum 24 mo) | 1 yr | 75% were in paid employment before illness onset vs. 29% at baseline. No employment data available from follow-up | Response rate: 98.7% (78/79). At FU: 8% no complaints, 38% less complaints, 37% similar, 17% had deteriorated. Spontaneous recovery was rare and only occurred in patients with an illness duration < 1.5 years |
| Vercoulen et al. (1996) [49] | Oxford | 298 CFS patients (comparison data from 53 HC) | 39 | 8.4 yrs (51 patients with illness duration of ≤2 yrs) | 18 mo | Employment status at baseline (BL) and at FU: 12% were unemployed; 28% (BL)and 29% (FU) worked; 43% (BL) and 42% (FU) were on sick leave/medically retired and 17% were housewife, retired or at school. | Response rate: 83% (246/298); 3% recovered; 17% improved, 60% remained unchanged and 20% had become worse |
| Vercoulen et al. (1997) [95] | Oxford | 51 CFS, 50 MS and 53 HC | 36.3 CFS | 5 yrs CFS | No FU | Working: 27% CFS, 28% MS and 47% HC. Invalidity benefits: 43% CFS, 32% MS and 2% HC. Total hours working: 10.4 CFS, 13.3 MS, 35.7 HC | No FU |
| Vincent et al. (2012) [96] | Fukuda | 151 (76 CFS, 75 IF) | 38.2 CFS (at fatigue onset) | 3.9 yrs CFS | No FU | CFS affected daily activities and work in 95% of cases | No FU |
| Wilson et al. (1994) [32] | Lloyd 1988 | 139 | 42.2 | 9.2 yrs | 3.2 yrs | 30% (31/103) patients unable to perform any work at FU and 25% (26/103) were receiving disability benefits because of CFS. No baseline data available for comparison. | Response rate: 74% (103/139); 37% did not improve, 20% could not perform any significant physical activity and 40% no social activity. Only 5.8% (6/103) had completely recovered |
| Zdunek et al. (2015) [97] | Fukuda | 2 groups of CFS patients: USA 162, UK 83 | USA 52.0 UK 45.9 | Unclear | No FU | Working full or part-time: 11.2% USA, 35.3% UK. On disability: 55.3% US, 35.4% UK. | UK more gradual onset, USA more sudden onset |
BL: baseline; CF: chronic fatigue; EBV: Epstein-Barr virus; FU: follow-up; HC: healthy controls; ICF: idiopathic chronic fatigue; IF: idiopathic fatigue; mo: months; MS: multiple sclerosis; yr: year; yrs: years.