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Water, sanitation and hygiene: interventions and diarrhoea – a review

Water, sanitation and hygiene: interventions and diarrhoea – a review. Lorna Fewtrell & Jack Colford. Introduction (1). Diarrhoeal disease continues to be one of the leading causes of morbidity and mortality in developing countries. Introduction (2). DIARRHOEA KILLS PEOPLE. Introduction (3).

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Water, sanitation and hygiene: interventions and diarrhoea – a review

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  1. Water, sanitation and hygiene: interventions and diarrhoea – a review Lorna Fewtrell & Jack Colford

  2. Introduction (1) • Diarrhoeal disease continues to be one of the leading causes of morbidity and mortality in developing countries

  3. Introduction (2) • DIARRHOEA KILLS PEOPLE

  4. Introduction (3) • The important role of sanitation and safe water in maintaining health has been recognised for centuries • 1980s – International Drinking Water Supply and Sanitation Decade • Reviews of the effectiveness of various levels of water supply and sanitation published

  5. Introduction (3)

  6. Objectives These are now quite dated so the objective of this review was to update the previous work in the area with a view to informing interested parties on the relative effectiveness of possible interventions addressing water, sanitation and hygiene.

  7. Search strategy (1) Medline and Embase databases searched using key words pairing, diarrhoea or intervention against: • Sanitation • Water quality • Water quantity • Hygiene • Drinking water

  8. Search strategy (2) • Database searches were restricted to papers relating to humans dated prior June 26, 2003 • The Esrey reviews were used to identify studies published prior to 1985 • Abstracts, where available, were examined – and papers which appeared to be relevant were obtained for further review

  9. Initial selection criteria • The article reported diarrhoea morbidity as a health outcome under endemic (or non-outbreak) conditions; and • The article reported specific water, sanitation and/or hygiene intervention(s), or some combination thereof

  10. Intervention classification (1) Hygiene – includes hygiene and health education and the encouragement of specific behaviours (such as handwashing) Sanitation – those interventions that provided some means of excreta disposal, usually the provision of latrines (at public or private level)

  11. Intervention classification (2) Water supply – included the provision of a new water source and/or improved distribution (such as installation of a handpump or a household connection) Water quality – these were related to the provision of water treatment, either at source or household level

  12. Intervention classification (3) Multiple – those which introduced water, sanitation and hygiene (or health education) elements to the study population

  13. Data extraction (1) • Study location • Study design • Study length • Study period • Sample size • Data collection method • Participant age band • Confounders examined

  14. Study design • Range of epidemiological study designs that can be (and in many cases, have been) applied to study the impact of improvements to water, sanitation and health: • Intervention • Case-control • Ecological

  15. Data extraction (2) • Illness definition • Recall period • Type & level of water supply and sanitation (pre-intervention) • Water source • Intervention • Relative risk and 95% CI

  16. Data extraction (3) • Relative risk included: • odds ratios, incidence density ratios, cumulative incidence ratios • When both adjusted and unadjusted (for other covariates) measures were reported – the most adjusted estimate was used

  17. Data extraction (4) • RR and 95% CI expressed such that a RR of less than unity means that the intervention group has a reduced frequency of diarrhoea in comparison to the control group

  18. Meta-analysis (intro) • Meta-analysis is a tool that allows the statistical pooling of data across studies to generate a summary estimate of effects • Where ‘effect’ is any measure of association between exposure and outcome (e.g. odds ratio) • It is not always appropriate to conduct a meta-analysis

  19. Meta-analysis(1) • Risk estimates from the selected studies were pooled in meta-analysis using STATA software (STATA Corporation, College Station, TX, USA, version 8) • STATA commands for meta-analysis are not an integral part of the original software but are additional, user-written, add-on programs that can be freely downloaded

  20. Meta-analysis(2) • Studies were stratified, prior to data analysis, into groups of related interventions • Studies were divided according to the level of country development and then analysed by intervention type

  21. Developing Countries Multiple (i.e. water, sanitation and hygiene [or health] education) Water supply Hygiene Sanitation Water quality Handwashing Education Community improvements Household connection Source Pt-of-use Meta-analysis (3)

  22. Meta-analysis(4) • Where sufficient studies were available within each intervention they were further examined in sub-group analysis defined by: • Health outcome • Age groups • Pre-intervention water and sanitation situation

  23. Pre-intervention scenarios • F – basic water and basic sanitation • Eb – improved water and basic sanitation • Ea – basic water and improved sanitation • D – improved water and improved san

  24. Meta-analysis(4) • Where sufficient studies were available within each intervention they were further examined in sub-group analysis defined by: • Health outcome • Age groups • Pre-intervention water and sanitation situation • Design • Location • Study quality

  25. Meta-analysis(5) • Forest plots and pooled estimates of risk were generated • Both fixed and random effects estimates were prepared for all analyses • If the heterogeneity is less than 0.2 - a random effects model was used

  26. Ref 1 Ref 2 Ref 3 Ref 4 Combined .01 .1 1 10 Effect Forest plot Random 0.757 (0.425 – 1.349) Fixed 0.582 (0.530 – 0.638) Heterogeneity p = 0.000

  27. Results

  28. Results

  29. Results

  30. Results

  31. Results Hypothetical example

  32. Results • All the data are outlined in the report • Following is a summary of the intervention studies reported from developing countries on an intervention-by intervention basis

  33. Hygiene

  34. Hygiene (1) • 15 papers • 13 studies • 11 included in the meta-analysis

  35. Hygiene (2) Random - 0.63 (0.52 – 0.76) Fixed - 0.75 (0.72 – 0.78) Heterogeneity - p = 0.000

  36. Hygiene (3) • Overall summary measure • 0.633 (0.524 – 0.765) • Removing poor quality studies • 0.547 (0.400 – 0.749)

  37. Hygiene (4) • Handwashing seemed to be more effective than hygiene education • There seemed to be a greater impact on diarrhoea than dysentery (but only 2 dysentery data points) • Intervention was effective whatever the baseline scenario, but more so where there was poorer water and/or sanitation facilities

  38. Hygiene (summary)

  39. Sanitation

  40. Sanitation (1) • 4 studies • 2 included in the meta-analysis (1 of which examined cholera) • Pooled estimate 0.678 (0.529 – 0.868) • Adding an additional study (1957 – USA) – pooled estimate 0.642 (0.514 – 0.802) • 1/5 not considered to be poor quality

  41. Water supply

  42. Water supply (1) • These included the provision of new or improved water supply and/or improved distribution • Complex – could include public OR private water supply

  43. Water supply (2) • 9 studies, 6 could be included in meta-analysis • Initial results suggested a significant impact – 0.749 (0.618 – 0.907) BUT that included an ecological study and one examining cholera

  44. Azurin and Alvero, 1974 Bahl, 1976 Ryder et al., 1985 Esrey et al., 1988 Wang et al., 1989 Tonglet et al., 1992 Combined .01 .1 1 10 Effect Water supply (3) Random – 0.75 (0.62 – 0.91) Fixed – 0.63 (0.63 – 0.64) Heterogeneity - p < 0.2

  45. Water supply (4) • Excluding the ecological study: • Pooled RR 0.869 (0.632 – 1.195) • Excluding the ecological study and restricting analysis to ‘standard’ diarrhoea • Pooled RR 1.031 (0.730 -1.457)

  46. Water supply (5) • Standpipe versus household on diarrhoea - suggests a small but not stat significant effect BUT…. • Only two studies considered to be of good quality – one of each: • HH 0.62 (0.59 – 0.65) • Standpipe 0.95 (0.88 – 1.00)

  47. Water supply (6) • In one of the hh connection studies, household storage was still practiced – omitting this study and adding two from developed countries (1976 UK; 1969 USA) – suggests that a household supply can be an effective intervention for reducing diarrhoea 0.557 (0.464 – 0.669)

  48. Water supply (summary)

  49. Water quality

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