Table 1. Study characteristics showing post-discharge long-term neurological sequelae.

The severity of COVID-19-associated illness was scored using an ordinal scale developed by a special World Health Organization (WHO) committee for use in randomized multi-center adaptive clinical trials and is based on the site of care (community or hospital) and intensity of oxygen supplementation required

SD: standard deviation; OR: odds ratio; CI: confidence interval; RT-PCR: reverse transcriptase polymerase chain reaction test; SONA: online research study management system

Study	Study design	Sample size	Age, years	Male gender (%)	Cases vs. control (column E)	Follow-up duration after discharge, days, mean ±SD/range	Neurocognitive effects/symptoms
Studies considered for meta-analysis (quantitative assessment of point estimate)
Jacobs et al., USA, Dec 2020 [7]	Prospective cohort study	183	57 (median)	111/183 (60.6%)	Cases: severe COVID-19 disease among hospitalized patients characterized by scores of five (non-invasive ventilation or high-flow oxygen), six (intubation and mechanical ventilation), or seven (ventilation plus additional organ support) vs. controls: mild COVID-19 disease among hospitalized patients characterized by scores of three (no oxygen therapy) or four (oxygen by mask or nasal prongs); subjects were scored using an ordinal scale developed by the WHO committee	35 ± 5 days	Headache - OR: 4.23, 95% CI: 2.15-8.32 (cases: 23/59 vs. control: 24/183); fatigue - OR: 0.93, 95% CI: 0.60-1.44 (cases: 82/149 vs. control 104/183); anosmia - OR: 1.96, 95% CI: 0.99-3.89 (cases: 17/65 vs. control: 28/183); myalgia - OR: 4.0498, 95% CI: 2.28-7.19 (cases:39/77 vs. control: 37/183); dysgeusia - OR: 1.0549, 95% CI :0.56-1.98 (cases: 18/79 vs. control: 40/183)
Fisher et al., USA, Jan 2021 [8]	Matched case-control study	320	40 (median)	151/320 (47.18%)	Cases: positive RT-PCR-confirmed SARS‐CoV‐2 infection (157) vs. control: negative RT-PCR-confirmed SARS‐CoV‐2 infection (163) at outpatient facilities	Interviews were conducted 15-52 days (median, 22 days) after the onset of symptoms	Fatigue - OR: 3.30, 95% CI: 2.60‐4.30 (cases: 121/157 vs. control: 91/163); anosmia - OR: 32.40, 95% CI: 12.60‐83.10 (cases: 98/157 vs. control 9/163); myalgia - OR: 3.30, 95% CI: 2.60‐4.30 (cases: 121/157 vs. control: 91/163)
Walsh-Messinger et al., USA, Nov 2020 [9]	Case-control study	148	19.86 (median)	1/22 (4.54%)	Cases: participants who reported with post-COVID-19 syndrome defined as protracted symptoms ≥28 days (n=22) vs. control A: participants who were never diagnosed with COVID-19 (n=58), and control B: participants who fully recovered (n=21)	Participants were recruited through SONA, an online research study management system; completed the online study about COVID-19 testing, symptoms, course of illness, treatment, and current functioning between October 7 and November 11, 2020, and the self-report measures were administered through Qualtrics (Qualtrics XM, Provo, UT)	Headache - OR: 9.33, 95% CI: 1.03-84.20 (cases: 7/22 vs. control B: 1/21); fatigue - OR: 10.45, 95% CI: 1.9281-56.6384 (cases: 19/22 vs. control B: 10/21); anosmia - OR: 4.09, 95% CI: 1.02-16.27 (cases: 18/22 vs. control B: 11/21); myalgia - OR: 2.33, 95% CI: 0.68-7.94 (cases: 14/22 vs. control: 9/21); dysgeusia - OR: 2.33, 95% CI: 0.68-7.94 (cases: 14/22 vs. control B: 9/21)
Studies considered for systematic review (qualitative assessment)
Halpin et al., UK, Feb 2021 [10]	Cross-sectional study	100 (68 ward patients and 32 ICU patients)	ICU patients' median age was 58.5 years, and for ward patients, it was 70.5 years	54/100 (54%)	Participants who were RT-PCR-confirmed and treated for COVID-19, out of which 32 participants required treatment in the intensive care unit (ICU group) and 68 participants were managed in hospital wards (ward group), and were screened using a specialist telephone screening tool designed to capture symptoms and report on post-discharge symptoms	Patients treated for COVID-19 were screened by telephone for 29-71 days post-discharge (mean: 48 days)	Fatigue - ICU group: 23/32, ward group: 41/68; OR: 1.6829, 95% CI: 0.68-4.19
Islam et al., Bangladesh, Feb 2021 [11]	Cross-sectional survey	1,002	34.7 (mean)	601/1,002(60%)	A self-reported online pre-tested semi-structured questionnaire was used to collect data over a one-month period involving people who had previously tested positive for COVID-19 and also the individuals who had recovered from COVID-19	Data taken over 1 month (September 11, 2020, to October 13, 2020)	Headache: 80/732 (10.92%), persistent: 8% of 1,002 = 80, ever: 73% = 732; fatigue: 120/810 (14.81%), persistent: 12% of 1,002 = 120, ever: 80.8% = 810; myalgia: 70/531 (13.18%), persistent: 7% of 1,002 = 70, ever: 53% = 531
Huang et al., USA, March 2021 [12]	Retrospective cohort study	1,407	Distributed across all age groups with persons aged 50-59 years (range, ±20 years) representing more than 72% of the long-hauler population. Included those aged ≤18 years in the long haulers group (34 participants, mean age of 9.29 years, 11/34 were aged ≤5 years)	653/1,407 (46%)	A sample of confirmed RT-PCR-positive SARS-CoV-2 patients and those who were never hospitalized for SARS-CoV-2 infection. Patients hospitalized for COVID-19 were excluded	Symptoms assessed at days 0-10 and 61+ among subjects with PCR-confirmed SARS-CoV-2 infection	380/1407 reported persistent symptoms after 60 days; headache: 111/120 (92.54%), 0-10 days: 120, 61+ days: 111; fatigue: 150/122 (123..22%) 0-10 days: 122, 61+ days: 150; anosmia: 25/52 (0.48%), 0-10 days: 52, 61+ days: 25; myalgia: 89/68 (131.59%), 0-10 days: 68, 61+ days: 89; dysgeusia: 47/56 (83.92%), 0-10 days: 56, 61+ days: 47
Carfi et al., Italy, July 2020 [13]	Retrospective cohort study	143	56.5 years (mean)	90/143 (63%)	Participants who were discharged from the hospital after COVID-19 recovery and who tested negative for SARS-CoV-2 were asked to score their quality of life from 0 (worst imaginable health) to 100 (best imaginable health) before COVID-19 and at the time of the visit. A difference of 10 points on the EuroQol visual analog scale was defined as worsened quality of life	Mean of 60 days (SD: 13.6) after symptom onset	Headache: 13/143 (9.1%); fatigue: 76/143 (53.1%); anosmia: 21/143 (14.69%); myalgia: 9/143 (6.29%); dysguesia: 14/143 (9.79%)