The Effects of Improved Housing on Malaria Transmission in Different Endemic Zones: A Systematic Review and Meta-Analysis.

IntroductionImproved housing has been shown to reduce the risk of malaria infections compared to traditional houses; however, it is unclear if the effects differ in different malaria transmission settings. This study evaluated the effects of improved housing on malaria transmission among different endemic areas. Methods and AnalysisElectronic databases, clinical trial registries and grey literature were searched for randomised controlled trials, cohort studies, case-control studies, and cross-sectional surveys on housing done between 1987 and 2022. Forest plots were done, and the quality of evidence was assessed using the Grading of Recommendations, Assessments, Development and Evaluation Framework. FindingsTwenty-two studies were included; twelve were cross-sectional, four were case-control, four were cohort studies and two were RCTs. RCTs indicated that modern houses did not protect against malaria compared to traditional houses. Cohort studies showed an adjusted risk ratio of 0.68 (95% CI 0.48 - 0.96) and Cross-sectional studies indicated an adjusted odds ratio (aOR) of 0.47 (95% CI 0.31 - 0.72). By endemic transmission regions, the adjusted odds ratio in the high endemic was 0.43 (95% CI 0.29 - 0.63); in the moderate transmission regions, aOR = 0.91 (95% CI 0.91 - 1.07) and in the low transmission settings, aOR = 0.42 (95% CI 0.26 - 0.66). ConclusionThe evidence from observational studies suggests that the risk reduction associated with modern housing is comparable or higher in low malaria transmission settings compared to high transmission settings. Evidence from RCTs in high-transmission settings shows that house improvements may induce risky behaviours such as staying outside for longer hours. Key MessagesO_LIIt is known that improved housing reduces the risk of malaria compared to traditional housing; however, the effects of improved housing in different endemic settings are unclear. C_LIO_LITo the best of our knowledge, this is the first time a systematic review and meta-analysis has stratified the effect measures of improved housing on malaria transmission in different transmission settings. C_LIO_LIOur study found no literature from high-quality research designs such as RCTs and Cohort studies on improved housing in low and moderate transmission settings. We call on researchers and funders to conduct and support high-quality research designs in low and moderate-transmission areas, especially in Africa, as more countries are reducing their malaria burdens due to increased interventions. This will help to achieve and sustain malaria elimination. C_LIO_LIPiecemeal improvements, such as closing eaves, screening and iron roofing, are not necessarily associated with a reduced risk of malaria. They may induce risky behaviours due to poor ventilation and higher indoor temperatures resulting in residents staying longer outside thus exposing themselves to infective mosquito bites. C_LI