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Table 1 Results and main conclusions relating to identified risk factors from included studies: risk of contraction

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

Disease contracted Ref Definition of risk factor Meta-analysis findings No. of studiesa Conclusionb
Comparison group Effect size (95% CI) Effect direction
Alcohol as a risk factor
 TB [18] Any alcohol use or higher amounts No alcohol or lower amounts OR 1.90 (1.63–2.23) 44
[19] Alcohol consumption N/A Unclear
 HIV [20] Binge drinking or alcohol misuse N/A 2
 Pneumonia [21] Any alcohol use or higher amounts No alcohol or lower amounts RR 1.83 (1.30–2.57) 14
[22] AUD No AUD RR 8.22 (4.85–13.95) 2
 IBD (IPD) [23] Alcohol consumption N/A 6
Illicit drug use as a risk factor
 TB [19] Drug abuse Unclear
[24] Injection drug use Unclear
 HIV [20] Injecting drugs, smoking crack cocaine 7
[25] Illicit drug use 7
[24] Injection drug use Unclear
 HCV [26] PWID Community based studies and blood donors Prevalence of HCV:  
PWID 44.71% (37.5–52.03) 46
Community 0.85% (0.00–3.98) 4
Blood donors 0.44% (0.40–0.49) 211
[27] PWID General population Prevalence of HCV:  
PWID 52.2% (46.9–57.5) 56
General pop. 0.3% (0.2–0.4) 122
[28] PWID General population Prevalence of HCV:  
PWID 53.6% (36.2–70.6) 15
General pop. 6.2% (5.7–6.7) 148
[29] PWID 7
Obesity as a risk factor
 Influenza [30] Obesity and morbid obesity 7
 Pneumonia [31] Obesity (BMI: 30–39.9 kg/m2) Normal weight CAP: RR 1.03 (CI 0.8–1.3) 10
Influenza related: RR 1.31 (1.05–1.63) 10
Nosocomial: RR 1.26 (0.80–1.98) 5
[32] Overweight and obesity Normal weight RR 1.33 (95% CI 1.04–1.71) 13
Smoking as a risk factor
 HIV [20] Current smoking 1
 Pneumonia [33] a) Current smoking Never smokers a) OR 2.17 (1.70–2.76) 13
b) Ever smoked   b) OR 2.31 (1.99–2.69) 13
 IBD (IPD) [23] Current or former smoking 6
Second-hand smoke as a risk factor
 TB [34] Exposure to ETS No exposure to ETS TB infection (children): OR 1.9 (0.9–2.9) 3
TB disease (children): OR 2.8 (0.9–4.8) 5
[35] Exposure to SHS No exposure to SHS TB infection (children): RR 1.19 (0.90–1.57) 6 ↑—
TB disease: RR 1.59 (1.11–2.27) 6
[36] Exposure to SHS No exposure to SHS TB infection: RR 1.67 (1.12–2.48) and adjusting for age/SES, RR 1.11 (0.90–1.57) 6
TB disease: RR 1.96 (1.37–2.80) and adjusting for age/SES, RR 2.13 (1.18–3.83) 12
 Pneumonia [33] Exposure to ECS No exposure to ECS Aged 65+: OR 1.64 (1.17–2.30) 2 ↑—
All ages: OR 1.13 (0.94–1.36) 5
 IBD [37] Exposure to SHS No exposure to SHS IMD: OR 2.02 (1.52–2.69) 16 ↑—
IHD: OR 1.22 (0.93–1.62) and 12
IHD (pre-schoolers) OR 1.46 (1.19–1.81) 9
IPD: OR 1.21 (0.69–2.14) 4
Physical inactivity as a risk factor
 Influenza
Pneumonia
[38] Lack of prolonged, moderate aerobic exercise 7
  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. OR Odds ratio, RR Relative risk, TB Tuberculosis, HIV Human immunodeficiency virus, HCV Hepatitis C virus, IBD Invasive bacterial disease, IPD Invasive pneumococcal disease, IMD Invasive meningococcal disease, IHD Invasive Hib disease, CAP Community acquired pneumonia, AUD Alcohol use disorder, BMI Body mass index, SHS Second-hand smoke, ETS Environmental tobacco smoke, ECS Environmental cigarette smoke, PWID People who inject drugs