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

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) 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

Introduction (3)

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17

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Water & Sanitation

Sanitation

Water Quality & Quantity

Water Quality

Water Quantity

Hygiene

% reduction in diarrhoeal illness

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.

Search strategy (1)

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

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

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

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)


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


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

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

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

Data extraction (2) Illness definition Recall period Type & level of water supply and sanitation

(pre-intervention) Water source Intervention Relative risk and 95% CI

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

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

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

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

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

Meta-analysis (3)Developing Countries

Multiple(i.e. water, sanitation and

hygiene [or health] education)

SanitationHygiene

Handwashing Education

Source Pt-of-use

Water quality

Community improvements

Household connection

Water supply

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

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

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

Meta-analysis(4)

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

Forest plot

Effect.01 .1 1 10

Combined

Ref 4

Ref 3

Ref 2

Ref 1

Random 0.757 (0.425 – 1.349)Fixed 0.582 (0.530 – 0.638)Heterogeneity p = 0.000

ResultsKey word search Initial number of references

Diarrhoea AND sanitation 636

Diarrhoea AND water quality 128

Diarrhoea AND water quantity

26

Diarrhoea AND hygiene 423

Drinking water AND intervention

111

Sanitation AND intervention 263

Hygiene AND intervention 459

Results

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3 32 2

1 10

5

14

4 4

0

2

4

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8

10

12

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16

Afr D Afr E Amr A Amr B AmrD Emr B Emr D Eur A Eur B Eur C Sear B Sear D Wpr A Wpr B

Results

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13

4

9

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2

4

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EME -Hygiene

EME -Sanitation

EME -Watersupply

EME -Waterquality

Dev -Hygiene

Dev -Sanitation

Dev -Watersupply

Dev -Waterquality

Dev -Multiple

ResultsRef Intervention Country Location Health

outcomeAge group

Result 95% CI

Black et al., 1981

Handwashing with soap

USA Suburban (child care centres)

Diarrhoea 0 – 36 months

0.52 0.36-0.76

Bartlett et al., 1988

Hygiene education

USA Urban (child care centres)


1.09

Kotch et al., 1994

Handwashing + hygiene education

USA Urban (child care centres)


0.84 0.50-2.08

Carabin et al., 1999

Hygiene education

Canada Unstated (child care centres)


0.77 0.51-1.18

Roberts et al., 2000

Handwashing Aus Urban (child care centres)


0.5 0.36-0.68

ResultsRef Adeq.

controlMeasure of confounders

Random. Health indicator definition

Health indicator recall

Analysis by age

Intervention /compliance assessed

Blinding Placebo

1 Yes Yes Yes Non standard

Daily Yes Yes No No

2 Yes Not clear Yes Non standard

Daily or twice weekly

NA No Some Some

3 No Yes No Non standard

2 weeks Yes Yes No No

4 Yes Yes Yes None Daily NA Yes Not clear No

5 Yes Yes Yes Standard 3 weeks Yes Yes Some No

Hypothetical example

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

Hygiene

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

Hygiene (2)

Effect.01 .1 1 10

Combined

Shahid et al., 1996

Pinfold and Horan, 1996

Haggerty et al., 1994a/b

Wilson et al., 1991

Lee et al., 1991

Han + Hlaing 1989

Alam et al., 1989

Stanton et al., 1988/ Stanton + Clemens 1987

Sircar et al., 1987

Torun, 1982

Khan, 1982Random - 0.63 (0.52 – 0.76)

Fixed - 0.75 (0.72 – 0.78)

Heterogeneity - p = 0.000

Hygiene (3) Overall summary measure

0.633 (0.524 – 0.765)

Removing poor quality studies 0.547 (0.400 – 0.749)

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

Hygiene (summary)

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Overall (11)

Excluding poor studies (8)

Scenario D (6)

Scenario E + F (4)

Education (6)

Handwashing (5)

Hw + diarrhoea (5)

Hw + dysentery (2)

% reduction in diarrhoea

Sanitation

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

Water supply

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

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

Water supply (3)

Effect.01 .1 1 10

Combined

Tonglet et al., 1992

Wang et al., 1989

Esrey et al., 1988

Ryder et al., 1985

Bahl, 1976

Azurin and Alvero, 1974 Random – 0.75 (0.62 – 0.91)Fixed – 0.63 (0.63 – 0.64)Heterogeneity - p < 0.2

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)

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)

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)

Water supply (summary)

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Water supply (diarrhoea)

Standpipe (diarrhoea)

HH connection (diarrhoea)

Water supply (overall)

'True' HH connection (diarrhoea)

Water quality

Water quality (1) 15 studies All had data suitable for inclusion in the

meta-analyses 5 papers judged to be poor quality

Water quality (2) Overall intervention effective – pooled

estimate 0.687 (0.534 – 0.885): 31% reduction

This included both source and household treatment

Water quality (3) Source treatment (3) Source only – a reduction in diarrhoea

seen but not stat significant. Some problems with the studies.

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

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

Water quality (summary)

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Overall

Source treatment

HH treatment

HH (excluding poor studies)

HH (rural)

HH (urban/periurban)

% reduction in diarrhoea

Multiple

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

Multiple interventions (2)

Effect.01 .1 1 10

Combined

Nanan et al., 2003

Messou et al., 1997

Hoque et al., 1996

Mertens et al., 1990a,b

Aziz et al., 1990Random - 0.69 (0.64 – 0.77)

Fixed - 0.72 (0.68 – 0.76)

Heterogeneity - p < 0.2

Overall summary

pooled effect

1

HH treatment - rural settings

HH treatment only

Source treatment only

Water quality

Standpipe and diarrhoea

HH connection and diarrhoea Diarrhoea only

Water supply

Sanitation

Education

Handwashing Excluding poor quality studies

Hygiene

Multiple

HH treatment - excl poor quality studies

HH treatment - urban + periurban settings

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

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?

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

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

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

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 >2 weeks

32% of studies (19 from 60) classed as poor! Results generally improved if these were removed

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

Discussion (pre-intervention) Most studies do not ascertain (or report)

pre-intervention diarrhoea level or water, sanitation and hygiene behaviour

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

Comparison with Esrey

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Hygiene Sanitation Watersupply

Waterquality

Multiple

Intervention

% r

educ

tion

in d

iarr

hoea

Esrey

Current

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

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

Conclusions In study terms in has to be said that

often:

WE COULD DO BETTER!

Conclusions If we do it right we can save lives –

we can make a difference

BUT……….

Thanks to Wayne Enanoria and Jack Colford Rachel Kaufmann Jamie Bartram and Dave Kay NAS, CDC, WELL, WASH, World Bank,

Water Aid, WHO, UNICEF

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

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