Methodological quality of the review: Medium confidence

Author: Heijnen M, Cumming O, Peletz R, Chan GK, Brown J, Baker K, Clasen T

Geographical coverage: Africa, Asia, South America and Oceania

Sector: Sanitation

Sub-sector: Health outcomes

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

More than 761 million people worldwide rely on shared sanitation facilities. These have historically been excluded from international sanitation targets, regardless of the service level, due to concerns about acceptability, hygiene and access.

Objectives:

To examine the evidence comparing the impact of shared sanitation versus individual household latrines (IHLs) on health outcomes.

Main findings:

A total of 22 studies were included in the review. Most studies were conducted in urban settings.  One study was conducted in Australia, three were conducted in Kenya and two each in India, Bangladesh and Egypt. One each was conducted in Brazil, Zambia, the Democratic Republic of Congo, Nigeria, Malawi, Zimbabwe, Taiwan, Jamaica, Ghana, Nepal, South Africa and Tanzania. Overall, studies were very diverse in terms of population and gender.

Review findings showed a pattern of increased risk of adverse health outcomes associated with shared sanitation compared to IHLs. A meta-analysis of 12 studies reporting on diarrhoea found increased odds of disease associated with reliance on shared sanitation (odds ratio (OR) 1.44, 95% CI: 1.18–1.76).

Authors concluded that evidence to date does not support a change of existing policy of excluding shared sanitation from the definition of improved sanitation used in international monitoring and targets. However, such evidence is limited, does not adequately address likely confounding, and does not identify potentially important distinctions among types of shared facilities. As reliance on shared sanitation is increasing, further research is necessary to determine the circumstances – if any – under which shared sanitation can offer a safe, appropriate and acceptable alternative to IHLs.

Methodology:

Studies were eligible for inclusion if they compared the health outcomes of populations relying on shared sanitation with those relying on IHLs. Shared sanitation included any type of facilities intended for the containment of human faeces and used primarily from home. Health outcomes included diarrhoea, helminth infections, enteric fevers, other faecal-oral diseases, trachoma and adverse maternal or birth outcomes. Studies were included regardless of study design, location, language or publication status.

Authors conducted a search on 19 databases, including two Chinese language databases (EMBASE, MEDINE, CAB abstracts, Global Health and HMIC). Conference proceedings from institutions were searched for relevant abstracts. In addition, government agencies, non-governmental organisations, universities and others involved in funding, implementing or investigating sanitation were contacted to solicit other studies that met the review’s inclusion criteria. Reference lists of studies were also reviewed.

Two authors independently screened studies for inclusion in the review. Relevant data of included studies was extracted by two authors independently. Observational studies were appraised using the Strengthening of the Reporting of Observational Studies in Epidemiology statement.

Authors conducted a meta-analysis using a random-effects model. No further synthesis was undertaken due to the limited number of studies reporting on other health outcomes.

Applicability/external validity:

Due to the quality of included studies and weak evidence, authors noted that results should be interpreted with caution and that the substantial differences among studies limited comparability.

Geographic focus:

Authors’ notes are based on studies conducted in low- and middle-income countries, apart from one study which was conducted in Australia. Therefore, findings and conclusions may be applicable to these settings.

Summary of quality assessment:

Overall, there is medium confidence in the conclusions about the effects of this study. Authors used appropriate methods to identify, screen studies for inclusion and to extract data and critically appraise included studies. However, methods used to analyse findings were not clear, as further details on the methods used to pool data for analysis were not reported. In addition, authors did not account for heterogeneity as part of the statistical analysis. Nevertheless, authors appropriately reported limitations of included studies and did not draw strong policy conclusions.