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Table 2 Results and main conclusions relating to identified risk factors from included studies: risk of more severe outcomes

From: The impact of behavioural risk factors on communicable diseases: a systematic review of reviews

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
  1. 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