Table 2.
Results and main conclusions relating to identified risk factors from included studies: risk of more severe outcomes
| Disease | Ref | Definition of more severe outcomes | Definition of risk factor (where recorded) | Meta-analysis (MA) findings | No. of studiesa | Conclusionb | |
|---|---|---|---|---|---|---|---|
| Comparison group | Effect size (95% CI) | Effect direction | |||||
| Alcohol as a risk factor | |||||||
| TB | [39] | Death | Alcoholism | – | Unclear | ↑ | |
| [40] | Treatment default, failure or death | Alcohol misuse | No alcohol misuse | RR 1.45 (1.21–1.74) | 15 | ↑ | |
| [41] | MDR TB | Alcohol use | – | 8 | ↑ | ||
| [19] | Poor outcomes | Alcohol use | – | Unclear | – | ||
| [42] | Relapse after treatment | Alcoholism | – | 1 | ↑ | ||
| [43] | Unsuccessful treatment | Alcohol use | No alcohol use | OR 2.0 (1.67–2.50) | 9 | ↑ | |
| [44] | Death, treatment failure, lost to follow up | Alcohol use | No or low alcohol use | DS-TB OR 1.99 (1.57–2.51) | 25 | ↑ | |
| MDR-TB OR 2.00 (1.73–2.32) | 18 | ||||||
| HIV | [45] | Poor treatment outcomes | Alcohol use disorders | – | 10 | ↑ | |
| [46] | Viral non-suppression | Alcohol use | No alcohol use | OR 2.47 (1.58–3.87) | 6 | ↑ | |
| [47] | HIV progression, survival | Alcohol use | – | 17 | ~ | ||
| HCV | [48] | No spontaneous clearance | Current/history of excess use | No history of excess use | OR 1.49 (1.05–2.13) | 5 | ↑ |
| [49] | No achievement of SVR | Alcohol use | – | 10 | ↑ | ||
| Illicit drug use a risk factor | |||||||
| TB | [39] | Death | Injection drug use | – | Unclear | ↑ | |
| [41] | MDR-TB | Drug abuse | – | 7 | ↑ | ||
| [19] | Poor outcomes | Drug abuse | – | Unclear | – | ||
| HIV | [50] | AIDS-related mortality | Regular/problem cocaine use | General pop. | SMR 23.12 (11.30–47.31) | 6 | ↑ |
| HCV | [48] | No spontaneous clearance | History of injection drug use | Non-injecting drug use | OR 1.69 (1.08–2.70) | 7 | ↑ |
| [51] | Reinfection with HCV | Recent drug use | Receiving OAT with no recent drug use | OAT: aRR 3.50 (1.62–7.53) | 21 | ↑ | |
| No OAT: aRR 3.96 (1.82–8.59) | 15 | ||||||
| [52] | No achievement of SVR | Recent People who inject drugs (PWID) | Non recent PWID | RR 1.01 (0.95–1.08) | 10 | – | |
| HBV/HDV | [53] | Infection with HDV (among those with HBV) | Intravenous drug users (IVDUs) | Mixed population, no risk factors | HDV seroprevalence: | ↑ | |
| IVDUs 37.57% (29.30–46.20) | 44 | ||||||
| Mixed pop. 10.58% (9.14–12.11) | 177 | ||||||
| Obesity as a risk factor | |||||||
| Influenza | [54] | ICU admission or death | a) Obesity, BMI ≥30 kg/m2 | a) Not obese | a) OR 2.14 (0.92–4.99) | 5 | ↑ |
| b) Morbid obesity ≥40 kg/m2 | b) Not morbidly obese | b) OR 2.01 (1.29–3.14) | 5 | ||||
| [30] | Higher level of healthcare | Obesity and morbid obesity | – | 7 | ↑ | ||
| [55] | Death | Obesity BMI > 30 kg/m2 | Not obese | OR 2.74 (1.56–4.80) | 33 | ↑ | |
| [56] | a) Hospital admission | Obesity BMI > 30 kg/m2 | Not obese | a) RR 1.82 (1.48–2.24) | 15 | ↑ | |
| b) ICU admission or death | b) Adults: RR 1.40 (1.01–1.95), | 24 | |||||
| Children: RR 0.91 (0.47–1.74) | 8 | ||||||
| COVID-19 | [57] | Poor outcomes | Obesity | 9 | ↑— | ||
| [58] | ICU admission, IMV or death | Obesity | Non-obese | RR 1.40 (0.91–2.17) | 3 | ↑ | |
| [59] | Worse outcomes | Obesity or overweight | 20 | ↑ | |||
| [60] | a) ICU admission | Obesity (BMI Asians > 25 kg | Non-obese | a) OR 1.21 (1.00–1.46) | 6 | ↑ | |
| b) IMV | /m2, Caucasians > 30 kg/m2) | b) OR 2.05 (1.16–3.64) | 5 | ||||
| Pneumonia | [32] | Mortality | Overweight and obesity | Normal weight | RR 0.83 (0.77–0.91) | 10 | ↓ |
| Smoking as a risk factor | |||||||
| TB | [39] | Death | Smoking | Unclear | – | ||
| [41] | DR TB | Smoking | 13 | ↑ | |||
| [19] | Poor outcomes | Smoking | Unclear | ↑ | |||
| [43] | Unsuccessful treatment | Smoking | 16 | ↑ | |||
| [40] | Treatment default, failure or death | Smoking | Non-smokers | RR 0.94 (0.75–1.19) | 11 | – | |
| [61] | a) Unfavourable outcomes | Current cigarette smoking | Non-smokers | a) OR 1.23 (1.14–1.33) | 8 | ↑ | |
| b) Delayed smear/culture conversion | b) OR 1.55 (1.04–2.07) | 5 | |||||
| [42] | Relapse after treatment | Smoking | 2 | ↑ | |||
| [62] | DR TB | Current/past smoking | Non-smokers | OR 1.57 (1.33–1.86) | 33 | ↑ | |
| Influenza | [56] | a) Hospital admission | Tobacco smoking | Non-tobacco smokers | a) RR 1.24 (1.07–1.43) | 10 | ↑ |
| b) ICU admission or death | b) RR 1.46 (1.25–1.69) | 30 | |||||
| COVID-19 | [63] | Adverse outcomes | Current smoking | Non-current smokers | OR 1.53 (1.06–2.20) | 18 | ↑ |
| [64] | ARDS, ICU admission or death | Smoking | Non-smokers | OR 1.54 (1.07–2.22) | 5 | ↑ | |
| [65] | ICU, severe oxygenation, IMV, death | Current smoking | Past/never smokers | RR 1.45 (1.03–2.04) | 2 | ↑ | |
| [66] | ICU admission or death | a) History of smoking | Non-smokers | a) OR 2.17 (1.37–3.46) | 16 | ↑ | |
| b) Current smoking | b) OR 1.51 (1.12–2.05) | 10 | |||||
| [67] | ICU, IMV or death | Active smoking | Non-smokers | All studies OR 1.98 (1.29–3.05) | 7 | ↑— | |
| One removed OR 1.55 (0.83–2.87) | 6 | ||||||
| [68] | Worsening of symptoms, ICU, death | a) Current smoking | Non-smokers | a) OR 1.98 (1.16–3.39) | 13 | ↑ | |
| b) Former smoking | b) OR 3.46 (2.46–4.85) | 4 | |||||
| Second-hand smoke as a risk factor | |||||||
| Pneumonia | [69] | Death from ALRIs (incl. pneumonia) | SHS exposure | No SHS exposure | (Children) OR 1.52 (1.20–1.93) | 8 | ↑ |
| Poor diet as a risk factor | |||||||
| HIV | [70] | HIV progression, mortality | Vit.D deficiency/insufficiency | 10 | ↑ | ||
| HCV | [49] | No achievement of SVR | Poor quality diet | 2 | – | ||
a Number of studies for either the meta-analysis or (for narrative reviews) the risk factor. b Conclusion statements are included in Supplementary file 2. Effect direction is based on conclusions: ↑ = increased risk; ↓ = decreased risk; — = no association; ~ = variable results. OR Odds ratio, RR Relative risk, aRR Adjusted rate ratio, SMR Standardised mortality ratio, TB Tuberculosis, DR-TB Drug-resistant tuberculosis, MDR-TB Multi-drug resistant tuberculosis, DS-TB Drug-susceptible tuberculosis, HIV Human immunodeficiency virus, AIDS Acquired immunodeficiency syndrome, HCV Hepatitis C virus, HBV Hepatitis B virus, HDV Hepatitis D virus, ARDS Acute respiratory distress syndrome, ARLI Acute lower respiratory infection, PWID People who inject drugs, IVDU Intravenous drug user, SHS Second-hand smoke, BMI Body mass index, SVR Sustained virological response, ICU Intensive care unit, IMV Invasive mechanical ventilation, OAT Opioid agonist therapy