Table 1.
GRADE quality of evidence for the association between modern housing and clinical malaria outcomes
| Outcomes | Summary of findings | Quality of the evidence | Overall quality of the evidence (GRADE) | |||||
|---|---|---|---|---|---|---|---|---|
| Relative effect (95 % CI) | No. participants (studies) | Risk of bias | Inconsistency | Indirectness | Imprecision | Publication bias | ||
| Malaria infection: Case–control, cross-sectional and cohort studies (crude OR) | OR 0°46 (0°33–0°62) | 22,700 (9 studies) | Serious1 | No serious inconsistency2 | No serious indirectness3 | No serious imprecision4 | Undetected5 | LOW1,2,3,4,5,6,7 due to risk of bias, large effect |
| Malaria infection: Case–control, cross-sectional and cohort studies (adjusted OR) | OR 0°53 (0°42–0°67) | 3949 (5 studies) | Serious1 | No serious inconsistency8 | No serious indirectness9 | No serious imprecision4 | Undetected5 | VERY LOW1,4,5,7,8,9,10 due to risk of bias |
| Clinical malaria: Case–control and cross-sectional studies (crude OR) | OR 0°32 (0°19–0°54) | 357 (1 study) | Serious1 | No serious inconsistency11 | Serious12 | No serious imprecision4 | Undetected13 | VERY LOW1,4,6,7,11,12,13 due to risk of bias, indirectness, large effect |
| Clinical malaria: Case–control and cross-sectional studies (adjusted OR) | OR 0°35 (0°20–0°62) | 357 (1 study) | Serious1 | No serious inconsistency11 | Serious12 | No serious imprecision4 | Undetected13 | VERY LOW1,4,6,7,11,12,13 due to risk of bias, indirectness, large effect |
| Clinical malaria: Cohort studies (crude RR) | RR 0°22 (0°14–0°35) | 1653 (3 studies) | Serious1 | No serious inconsistency14 | Serious15 | No serious imprecision4 | Undetected13 | LOW1,4,7,13,14,15,16 due to risk of bias, indirectness, large effect |
| Clinical malaria: Cohort studies (adjusted RR) | RR 0°55 (0°36–0°84) | 2237 (3 studies) | Serious1 | No serious inconsistency17 | Serious15 | No serious imprecision4 | Undetected13 | VERY LOW1,4,13,15,17,18 due to risk of bias, indirectness |
Patient or population: People of all ages living in malaria-endemic regions
Settings: East Timor, Egypt, Ethiopia, Greece, Malawi, Mexico, Sri Lanka, Tanzania, Thailand, Uganda and Yemen
Intervention: modern (versus traditional) housing
GRADE Working Group grades of evidence: High quality: Further research is very unlikely to change confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on confidence in the estimate of effect and is likely to change the estimate. Very low quality: The estimate is very uncertain
1Downgraded by 1 for serious risk of bias: All studies were non-randomized and observational
2No serious inconsistency: All nine studies observed a protective effect of modern housing, compared to traditional housing. The smallest effect was a 28 % reduction in the odds of malaria infection
3No serious indirectness: These nine studies were conducted in a variety of sites, both urban and rural, in settings across sub-Saharan Africa, Asia and Europe. The findings are generalizable elsewhere
4No serious imprecision: The overall effect was statistically significant and clinically important
5Publication bias not detected: Egger's test for bias in crude results found no evidence funnel plot asymmetry (bias coefficient 0.52, 95 % CI −1.61 – 2.65, p = 0.60)
6Upgraded by 1 for large effect: OR lies within the range 0 to 0.5
7No evidence that residual confounding would reduce the demonstrated effect: no significant difference between crude and adjusted effects
8No serious inconsistency: All five studies observed a protective effect of modern housing, compared to traditional housing. The smallest effect was a 27 % reduction in the odds of malaria infection
9No serious indirectness: These five studies were conducted in a variety of sites, both urban and rural, in sub-Saharan Africa and Asia. The findings are generalizable elsewhere
10No large effect: Odds Ratio does not fall into the range 0 to 0.5
11No serious inconsistency: only one study
12Downgraded by 1 for indirectness: only one study was included, which was conducted in rural Mexico and the findings may not be generalizable elsewhere
13Publication bias not detected: insufficient studies to construct funnel plots
14No serious inconsistency: all three studies observed a protective effect of modern housing, compared to traditional housing. The smallest effect was a 53 % reduction in incidence of clinical malaria
15Downgraded by 1 for serious indirectness: all studies were conducted in rural sub-Saharan Africa. The results may not be generalizable to other settings
16Upgraded by 2 for very large effect: Rate ratio and 95 % confidence intervals lie within the range 0 to 0°5
17No serious inconsistency: all three studies observed a protective effect of modern housing, compared to traditional housing. The smallest effect was a 25 % reduction in the incidence of clinical malaria
18No large effect: RR does not fall into the range 0 to 0°5