Showing characteristics and risk of bias assessment of the included observation studies
| Authors (reference) | No of participants Design Place of study | Clinical outcomes reported | Covariates adjusted for | NOS * | ||
| Statin users | Statin non-users | Adjusted estimate | ||||
| Gupta et al 4 | 1296† Retrospective multicentre cohort study, USA | In-hospital 30 days mortality | Age, male sex, history of atrial arrhythmias, and DM | 8/9 | ||
| 96/648 (14.8%) | 172/648 (26.5%) | OR=0.49 (0.38, 0.63) | ||||
| Zhang et al 5 ‡ | 4305† Retrospective multicentre cohort study, China | Mortality | Age, sex, oxygen saturation at admission | 8/9 | ||
| 45/861 (5.2%) | 325/3444 (9.4%) | HR=0.58 (0.43, 0.80) | ||||
| Alamdari et al 6 | 459 Retrospective single centre cohort study, Iran | Mortality | NR | 6/9 | ||
| 6/117 (5.1%) | 57/342 (16.7%) | NR | ||||
| Daniels et al 7 | 170 Retrospective single centre cohort study, USA | ICU admission or mortality | Age, sex, comorbidities (obesity, HTN, DM, CVD, and CKD) | 7/9 | ||
| 20/46 (43.5%) | 70/124 (56.5%) | OR=0.29 (0.11, 0.71) | ||||
| De Spiegeleer et al 8 | 154 Retrospective multicentre cohort study, Europe | Hospital stay or mortality | Age, sex, functional status, DM, HTN | 6/9 | ||
| 6/31 (19.4%) | 31/123 (25.2%) | OR=0.75 (0.24, 1.87) | ||||
| Song et al 9 | 249 Retrospective single centre cohort study, USA | Mortality | Age, sex, race, CVD, COPD, DM, obesity. | 7/9 | ||
| 27/123 (21.9%) | 15/126 (11.9%) | OR=0.88 (0.37, 2.08) | ||||
| Yan et al 11 | 578 Retrospective multicentre case control Study, China | Severe and critical disease | NR | 5/9 | ||
| 5/15 (33.3%) | 123/563 (21.8 %) | NR | ||||
| McCarthy et al 12 | 247 Multi-centre cohort, USA | ICU admission or mortality | NR | 5/9 | ||
| 51/107 (47.7%) | 61/140 (43.6%) | NR | ||||
| Krishnan et al 13 | 152 Retrospective multicentre cohort study, USA | Mortality | NR | 5/9 | ||
| 57/81 (70.4%) | 35/71 (49.2%) | NR | ||||
| Rodriguez-Nava et al 19 ‡ | 87 Retrospective single centre cohort study, USA | Mortality | Age, HTN, CVD, severity, invasive mechanical ventilation, and antibiotics (except azithromycin) | 6/9 | ||
| 23/47 (48.9%) | 25/40 (62.5%) | HR=0.38 (0.18, 0.77) | ||||
| Nicholson et al 20 | 1042 Retrospective multicentre cohort study, USA | Mortality | Age, sex, ethnicity, comorbidities, smoking, aspirin, albumin, CRP, PCT and haematological parameters | 7/9 | ||
| 122/510 (23.9%) | 89/530 (16.8%) | OR=0.502 (0.273, 0.926) | ||||
| Butt et al 21 | 4842 Observational nationwide cohort study, Denmark | All-cause mortality | Age, sex, ethnicity, socioeconomic status and comorbidities | 8/9 | ||
| 177/843 (21.0%) | 311/3999 (7.8%) | HR=0.96 (0.78, 1.18) | ||||
| Masana et al 22 | 2157 Retrospective multicentre cohort study, Spain | Mortality | Distance, age, sex, smoking status, comorbidities | 7/9 | ||
| 115/581 (19.8%) | 238/1576 (15.1%) | HR=0.58 §
(0.39, 0.89) | ||||
| Saeed et al 23 | 4252 Retrospective single centre cohort study, USA | Cumulative in-hospital mortality | Age, sex, history of AHD, Charlson comorbidity index, presenting vitals, serum glucose, lactic acid, creatinine and intravenous antibiotic use during hospitalisation | 8/9 | ||
| 311/1355 (23.0%) | 782/2897 (27.0%) | HR=0.51 ¶
(0.43, 0.61) | ||||
Clinical outcome data reported as n/N (%).
OR/HR presented as ratio (95% CI).
*Risk of bias assesssment was performed using NOS.
†Number of participants after applying propensity score-matching model to minimise differences in baseline characteristics between statin users versus non-statin users.
‡Studies reporting in-hospital use of statins.
§HR calculated 581 statin users and 581 genetic matched statin non-users.
¶HR calculated only for COVID-19 patients with diabetes mellitus (n=2266) with 983 being statin users and 1283 being statin non-users.
**
AHD, atherosclerotic heart disease; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; CRP, C reactive protein; CVD, cardiovascular disease; DM, diabetes mellitus; HTN, hypertension; ICU, intensive care unit; NOS, Newcastle-Ottawa Scale; NR, not reported; OSA, obstructive sleep apnoea; PCT, procalcitonin.