Water, sanitation and hygiene: interventions and diarrhoea a review

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Water, sanitation and hygiene interventions and
diarrhoea a review

• Lorna Fewtrell Jack Colford

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Introduction (1)

• Diarrhoeal disease continues to be one of the
  leading causes of morbidity and mortality in
  developing countries

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Introduction (2)

• DIARRHOEA KILLS PEOPLE

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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

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Introduction (3)
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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.

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Search strategy (1)

• Medline and Embase databases searched using key
  words pairing, diarrhoea or intervention against
• Sanitation
• Water quality
• Water quantity
• Hygiene
• Drinking water

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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

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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

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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)

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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

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Intervention classification (3)

• Multiple those which introduced water,
  sanitation and hygiene (or health education)
  elements to the study population

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Data extraction (1)

• Study location
• Study design
• Study length
• Study period
• Sample size
• Data collection method
• Participant age band
• Confounders examined

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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

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Data extraction (2)

• Illness definition
• Recall period
• Type level of water supply and sanitation
  (pre-intervention)
• Water source
• Intervention
• Relative risk and 95 CI

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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

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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

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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

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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

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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

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Meta-analysis (3)
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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

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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

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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

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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

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Forest plot
Random 0.757 (0.425 1.349) Fixed 0.582 (0.530
0.638) Heterogeneity p 0.000
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Results
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Results
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Results
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Results
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Results
Hypothetical example
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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

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Hygiene
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Hygiene (1)

• 15 papers
• 13 studies
• 11 included in the meta-analysis

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Hygiene (2)
Random - 0.63 (0.52 0.76) Fixed - 0.75 (0.72
0.78) Heterogeneity - p 0.000
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Hygiene (3)

• Overall summary measure
• 0.633 (0.524 0.765)
• Removing poor quality studies
• 0.547 (0.400 0.749)

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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

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Hygiene (summary)
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Sanitation
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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

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Water supply
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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

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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

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Water supply (3)
Random 0.75 (0.62 0.91) Fixed 0.63 (0.63
0.64) Heterogeneity - p lt 0.2
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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)

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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)

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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)

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Water supply (summary)
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Water quality
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Water quality (1)

• 15 studies
• All had data suitable for inclusion in the
  meta-analyses
• 5 papers judged to be poor quality

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Water quality (2)

• Overall intervention effective pooled estimate
  0.687 (0.534 0.885)
• 31 reduction
• This included both source and household treatment

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Water quality (3)

• Source treatment (3)
• Source only a reduction in diarrhoea seen but
  not stat significant. Some problems with the
  studies.

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Water quality (4)

• Household treatment/safe storage (12)
• Household treatment effective 0.645 (0.475
  0.875)
• 35 reduction
• Impact increased if poor quality studies are
  removed from the analysis
• 39 reduction

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Water quality (5)

• Examining the effect of study location on the
  intervention, showed that there seemed to be a
  greater impact seen on diarrhoea in people from
  rural communities
• 47 reduction
• compared to urban/periurban settings
• 23 reduction

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Water quality (summary)
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Multiple
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Multiple interventions (1)

• Nine papers
• 7 studies, 6 of which had risk estimates and 5 of
  which were used in the meta-analysis
• 5/6 risk measures less than 1

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Multiple interventions (2)
Random - 0.69 (0.64 0.77) Fixed - 0.72 (0.68
0.76) Heterogeneity - p lt 0.2
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Overall summary
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Discussion (hygiene)

• Most conducted where water and sanitation already
  improved
• Seem to be effective whatever the starting
  conditions
• Actual interventions vary widely
• Diarrhoeal reductions improved when poor papers
  excluded

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Discussion (sanitation)

• Few studies looked at actual sanitation
  interventions
• Most (75) were classified as poor quality
• Meta-analysis does suggest that the intervention
  is effective
• Scope for much more work here dry sanitation
  study?

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Discussion (water supply)

• Public and private supplies
• Compliance generally poorly assessed, with few
  data on water usage
• Suggestion that household connection is effective
  in reducing diarrhoea levels, especially bringing
  in 2 studies conducted in developed countries

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Discussion (water quality)

• Source treatment and household treatment
• Household treatment particularly effective
  (especially when poor quality papers removed from
  analysis)
• Range of household treatment types
• Source treatment studies hampered by
  methodological problems

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Discussion (multiple)

• Complex! All provided water supply, sanitation
  and hygiene measures but final provision varied
• None reported final water quality (after storage)
  and none employed household treatment
• Lack of additive effect, when compared to single
  interventions disappointing

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Discussion (study quality)

• Studies classified as poor quality if
• Lack of adequate control group
• No measurement of confounding factors
• Undefined health indicator and/or
• Health indicator recall of gt2 weeks
• 32 of studies (19 from 60) classed as poor!
  Results generally improved if these were removed

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Discussion (baseline scenario)

• Reasonable to expect diarrhoea reduction to be
  dependent upon starting conditions
• F basic water, basic sanitation
• Eb improved water, basic sanitation
• Ea basic water, improved sanitation
• D improved water, improved sanitation
• Not surprisingly, most studies were conducted in
  areas classified as F so not possible to
  examine except for hygiene

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Discussion (pre-intervention)

• Most studies do not ascertain (or report)
  pre-intervention diarrhoea level or water,
  sanitation and hygiene behaviour

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Discussion (hh storage)

• Household storage of water prior to consumption
  is common
• In many intervention studies (except hh treatment
  ones), this is often not considered
• Contamination of stored water is extremely common

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Comparison with Esrey
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Conclusions

• Some 15 years on from Esrey et al. and over 20
  years from Blum and Feachem diarrhoea is still
  killing people in developing countries
• Loosing data
• Poor community involvement

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Conclusions

• There is a lot more that we could look at
• Water usage
• Sustainability of the interventions
• Sustainability of the health effects
• Different ways of encouraging intervention uptake
• Other health outcomes

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Conclusions

• In study terms in has to be said that often
• WE COULD DO BETTER!

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Conclusions

• If we do it right we can save lives we can make
  a difference
• BUT.

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Thanks to

• Wayne Enanoria and Jack Colford
• Rachel Kaufmann
• Jamie Bartram and Dave Kay
• NAS, CDC, WELL, WASH, World Bank, Water Aid, WHO,
  UNICEF