Effect of Intensive Handwashing Promotion on Childhood Diarrhea in High-Risk Communities in Pakistan (2024)

ContextWashing hands with soap prevents diarrhea, but children at the highestrisk of death from diarrhea are younger than 1 year, too young to wash theirown hands. Previous studies lacked sufficient power to assess the impact ofhousehold handwashing on diarrhea in infants.

ObjectiveTo evaluate the effect of promoting household handwashing with soapamong children at the highest risk of death from diarrhea.

Design, Setting, and ParticipantsA cluster randomized controlled trial of 36 low-income neighborhoodsin urban squatter settlements in Karachi, Pakistan. Field workers visitedparticipating households at least weekly from April 15, 2002, to April 5,2003. Eligible households located in the study area had at least 2 childrenyounger than 15 years, at least 1 of whom was younger than 5 years.

InterventionsWeekly visits in 25 neighborhoods to promote handwashing with soap afterdefecation and before preparing food, eating, and feeding a child. Withinintervention neighborhoods, 300 households (1523 children) received a regularsupply of antibacterial soap and 300 households (1640 children) received plainsoap. Eleven neighborhoods (306 households and 1528 children) comprised thecontrol group.

Main Outcome MeasureIncidence density of diarrhea among children, defined as the numberof diarrheal episodes per 100 person-weeks of observation.

ResultsChildren younger than 15 years living in households that received handwashingpromotion and plain soap had a 53% lower incidence of diarrhea (95% confidenceinterval [CI], –65% to –41%) compared with children living incontrol neighborhoods. Infants living in households that received handwashingpromotion and plain soap had 39% fewer days with diarrhea (95% CI, –61%to –16%) vs infants living in control neighborhoods. Severely malnourishedchildren (weight for age z score, <–3.0)younger than 5 years living in households that received handwashing promotionand plain soap had 42% fewer days with diarrhea (95% CI, –69% to –16%)vs severely malnourished children in the control group. Similar reductionsin diarrhea were observed among children living in households receiving antibacterialsoap.

ConclusionIn a setting in which diarrhea is a leading cause of child death, improvementin handwashing in the household reduced the incidence of diarrhea among childrenat high risk of death from diarrhea.

Nearly 2 million children die annually from diarrheal disease.¹ A recent meta-analysis concluded that handwashingpromotion interventions decrease diarrhea by a mean of 47%.² Theauthors estimate that such interventions could prevent 1 million child deathsper year.² However, the systematic meta-analysisand the studies it included summarized the reduction in diarrheal rates amongall children or all family members. But all family members are not at equalrisk of death from diarrhea. Children younger than 5 years are at much higherrisk of death from diarrhea than older children and adults,¹ andinfants (younger than 1 year) are at the highest risk of death. Verbal autopsystudies from Egypt,³ Pakistan,⁴ Bangladesh,⁵ and Ethiopia⁶ reportthat 43% to 78% of deaths from diarrhea among children younger than 5 yearsoccur in the first year of life.

Infants cannot wash their own hands and therefore cannot interrupt thetransfer of pathogens between their hands and their mouth. Infants might benefitfrom a lower rate of diarrheal pathogen transmission from parents and siblingswho wash their hands more frequently with soap but the benefit to the infantmight be quite different from the overall benefit.

We identified only 2 handwashing intervention trials from developingcountries that reported diarrheal rates among infants.^7,8 In1 study in which the intervention assignment was randomized,⁷ theanalysis accounted for the cluster design but the measured 24% reduction indiarrheal disease among children younger than 1 year was not significantlydifferent from the control group. A second handwashing promotion study⁸ reported a 61% reduction in diarrheal disease amongchildren younger than 1 year but there was only 1 intervention handwashingpromotion community and 1 control community. The data were analyzed at theindividual level and the repeated measures of each individual were not accountedfor in the analysis.⁸

In addition to young age, malnutrition^9-11 andpersistent diarrhea^10,12,13 areimportant risk factors for death from diarrhea. We cannot identify any handwashingintervention trials that evaluated effectiveness among malnourished childrenor for persistent diarrhea. Thus, the effectiveness of handwashing with soapin preventing diarrhea among the most vulnerable children is unclear.

In Karachi, Pakistan, more than 4 million low-income residents livein squatter settlements where they do not own legal title to the land andmunicipal infrastructure is limited.¹⁴ A verbalautopsy study from these communities concluded that 41% of all childhood deathsyounger than 5 years were due to diarrhea.¹⁵ Seventy-threepercent of these diarrheal deaths occurred among infants.¹⁵ Weevaluated whether promoting washing hands with soap decreased diarrhea amongchildren at the highest risk of death from diarrhea in Karachi squatter settlements.

The Karachi Soap Health Study was conducted in adjoining multiethnicsquatter settlements in central Karachi—Bilal, Hazara, Manzoor, andMujahid colonies—in collaboration with Health Oriented Preventive Education(HOPE), a nongovernmental organization that operates local health clinicsand supports community-based health and development initiatives.

Most residents in these communities have household toilets but the dischargeflows into open sewers. After defecation, toilet paper is rarely used. Instead,residents routinely rinse their anus with water from a pitcher. Although handwashing,typically with water alone, is part of ritual preparation for prayer in thesecommunities, thorough washing of hands with soap is less common, even thoughaffordable hand soap is widely available throughout these communities fromsmall neighborhood shops. The water used for drinking and handwashing in thesecommunities is heavily contaminated with fecal organisms.¹⁶ Handsare typically dried on clothing. Clothing is usually laundered after severaldays of wear.

Field workers identified 42 candidate neighborhoods of 60 to 273 households,separated from one another by a street or market area. Field workers conducteda census of these neighborhoods, and before intervention assignment, identifiedand obtained informed consent from 1050 households. Eligible households werelocated in the study area, had at least 2 children younger than 15 years,at least 1 of whom was younger than 5 years, and planned to continue to residein their homes for the duration of the study.

The field workers listed the candidate neighborhoods in order of proximityto their field center. One of the investigators not involved in recruitingneighborhoods or households (S.P.L.) programmed a spreadsheet to generaterandomly the integers 1 or 2 with twice the probability of generating a 2vs a 1. He applied the random numbers sequentially to the list of neighborhoods.Those neighborhoods with a 1 were assigned to control and those with a 2 wereassigned to handwashing promotion. Random assignment continued until neighborhoodscomprising 600 handwashing promotion households and 306 control householdswere assigned. Ultimately, 25 neighborhoods were assigned to handwashing promotionand 11 to control (Figure 1). Handwashingpromotion was assigned at the neighborhood level because a number of the handwashingpromotion activities were neighborhood-level activities. Antibacterial vsplain soap was randomly assigned at the household level.

Handwashing Promotion. Field workers conductedneighborhood meetings about handwashing. They used slide shows, videotapes,and pamphlets to illustrate health problems resulting from contaminated handsand to provide specific handwashing instructions. The core handwashing promotionactivity was regular, at least weekly, household visits by the field workers.Each field worker spoke the first language of the study households they visited.They described in detail the importance of handwashing. They encouraged participantsto wet their hands, lather them completely with soap, and rub them togetherfor 45 seconds. Hands were typically dried on the participants' clothing.Field workers encouraged all persons in intervention households old enoughto understand (generally those participants older than 30 months) to washtheir hands after defecation and cleaning an infant who had defecated, andbefore preparing food, eating, and feeding infants. They encouraged adoptingregular handwashing habits. Field workers also encouraged participants tobathe once a day with soap and water. Field workers encouraged questions anddiscussion about handwashing. They resupplied the families with soap as needed.Field workers did not provide educational messages on water treatment, foodhygiene, or other strategies to decrease diarrhea.

Soap. The antibacterial soap contained 1.2%triclocarban as an antibacterial agent. The plain soap was identical to theantibacterial soap with the single exception that it did not contain triclocarban.Both soaps were provided as 90-g white bars without a brand name or symboland packaged identically in a generic white wrapper. Cases of 96 bars wereidentified by serial numbers that were matched to households. Neither thefield workers nor the families knew whether the family's soap was antibacterialor plain.

Control. Field workers provided control householdswith a regular supply of children's books, notebooks, pens, and pencils tohelp with their children's education but no products that would be expectedto affect diarrhea. Field workers neither encouraged nor discouraged handwashingin control households. Field workers visited control and intervention householdswith equal frequency to collect health outcome data but the visits were shorterin control households because no health education or encouragement for behaviorchange was provided.

Field workers recruited from the study or nearby communities were extensivelytrained in interviewing techniques, data recording, approaches to promotehandwashing, and measuring and weighing children. The same field workers promotedhandwashing and collected outcome data during their household visits.

Trained field workers conducted a preintervention baseline survey ofhousehold characteristics. They identified each child (aged <15 years)in the household. Children's dates of birth were confirmed with birth certificatesor immunization records. Field workers visited participating households atleast weekly for 1 year (April 15, 2002, to April 5, 2003) and asked the motheror other caregiver if the children had diarrhea (≥3 loose stools within24 hours) in the preceding week, and, if so, for how many days. Typically,field workers visited each household twice during the week to ensure thatepisodes of diarrhea from both early and late in the week were recalled. Supervisorsrevisited 40% of homes each week and reviewed the history of diarrhea amongfamily members. The history recorded by the supervisor was compared with thehistory recorded by the field worker and, if there was a discrepancy, thefieldworker and supervisor revisited the house to clarify the difference.

Field workers weighed participating children younger than 5 years atbaseline and every 4 months. Field workers weighed children 3 years or youngerby using a hanging scale (Salter, Tonbridge, Kent, England) and children olderthan 3 years by using a bathroom scale. We calculated weight for age z scores to compare the study children's weight with theNational Center for Health Statistics standards. The z scorerepresents the number of standard deviations that the child's measured weightfor age differs from the standard healthy population. We calculated the meanweight for age z score from the multiple weighingsessions throughout the study for each child. We classified children as moderatelymalnourished if their mean weight for age z scorewas less than –2.0 and −3.0 or higher, and severely malnourishedif their mean weight for age z score was less than–3.0.

A primary hypothesis of the Karachi Soap Health Study was that promotinghandwashing with antibacterial or plain soap would significantly reduce theamount of diarrheal illness compared with standard habits and practices inthe control group. (Other primary hypotheses of the Karachi Soap Health Studyaddress the effectiveness of bathing and handwashing with antibacterial orplain soap in preventing impetigo and acute respiratory illness and will bereported separately.) A primary study outcome was the incidence density ofdiarrhea (ie, the number of new episodes of diarrhea divided by the at-riskperson-weeks of observation). We considered a child at risk for a new episodeof diarrhea if he or she reported no diarrhea in the previous week. We alsomeasured disease outcome using longitudinal prevalence because it is moreclosely associated with growth faltering and child mortality than is diarrheaincidence.¹⁷ We calculated longitudinal prevalenceby summing the number of days each child had diarrhea and dividing by thetotal number of days of observation.

We calculated a sample size of 239 households per intervention group,assuming 1.2 episodes of diarrhea per 100 person-weeks among children youngerthan 15 years in the control group, 25% lower incidence of diarrhea in eachhandwashing promotion group vs control, 3.8 children per household, and adoubling of sample size to offset the effect of clustering by neighborhoodand repeated measures. We increased the sample size to 300 households perintervention group to assess other health outcomes, which will be reportedseparately.

Because we assigned soap promotion vs control at the neighborhood level,we analyzed the comparison of outcomes at the neighborhood level. Specifically,within each neighborhood among person-weeks within the subgroup of interest,we identified the total number of new episodes of diarrhea or days of diarrheaand divided it by the total number of person-weeks at risk for children inthat neighborhood within the subgroup of interest. We calculated rates byintervention assignment by taking the mean of the appropriate neighborhoodrates, weighted by the person-weeks of observation from each neighborhoodthat contributed to the mean. We calculated rate ratios by dividing the weightedmeans from intervention neighborhoods by the weighted means from control neighborhoods.¹⁸ We calculated 95% confidence intervals around theserate ratios using Taylor Series approximations to obtain SEs.¹⁹ Thisapproach calculated confidence intervals (CIs) that reflected the differentdistribution of proportions at the neighborhood level. We report the percentagedifference in outcome between intervention and control (ie, rate ratio minus1). The disease experience of each child, household, and neighborhood wastracked and analyzed with the group they were originally assigned to (ie,intention-to-treat analysis). We considered P≤.05as statistically significant. We used SAS version 9.0 and JMP version 5.0(SAS Institute Inc, Cary, NC) to conduct the statistical analysis.

Community leaders and heads of households provided informed consent.Ill children were assessed by field workers and referred to the appropriatelevel of health care. The first line of treatment for diarrhea was oral rehydrationsolution. Ill children referred by field workers were offered clinical servicesfree of charge at HOPE health care facilities located in these communities.The study protocol was approved by the ethics review committee of the AgaKhan University and an institutional review board of the Centers for DiseaseControl and Prevention.

The 36 neighborhoods in the study included a median 115 households (range,60-273 households). A median of 21% of households in each neighborhood (range,6%-39%) met the eligibility criteria for the study. All eligible householdschose to enroll. Thus, for the study, a median 26 households participatedper neighborhood (range, 9-37; interquartile range, 21-30). Within the 25neighborhoods randomized to handwashing promotion, 300 households (1523 children)were randomized to receive antibacterial soap and 300 households (1640 children)were randomized to receive plain soap (Figure1). Eleven neighborhoods, representing 306 households and 1528 children,were randomized to the standard habits and practices control group. During51 weeks of follow-up, diarrhea outcome information was collected on 210133person-weeks, representing 89% of the study populations' experience (88% inantibacterial soap, 89% in plain soap, and 89% in control households). Themost common reason for failure to collect information was that study participantshad temporarily left the city to visit relatives. There was a discrepancybetween the field worker's record of diarrhea symptoms and the supervisor'srecord in less than 1% of supervisory visits.

At baseline, households in the 3 intervention groups were of similarsize and socioeconomic status, had a comparable number of young children,a similar proportion of whom were malnourished, similar sources of water,sanitary facilities, and reported hand soap purchases (Table 1). Mothers reported breastfeeding their children youngerthan 2 years during 95% of child-weeks of observation in the antibacterialsoap group, 95% in the plain soap group, and 94% in the control group. Exclusivebreastfeeding was less common. Mothers reported exclusively breastfeedingtheir infants during 43% of infant-weeks of observation in the antibacterialsoap group, 42% in the plain soap group, and 45% in the control group.

During the course of the study, handwashing promotion households receiveda mean 3.3 bars of the study soap per week; this translates into each householdresident using a mean 4.4 g/d of soap.

Compared with children living in control neighborhoods, children livingin households that received plain soap and encouragement to wash their handshad a 53% lower incidence of diarrhea (95% CI, –65% to –41%) anda 50% lower longitudinal prevalence of diarrhea (95% CI, –65% to –35%; Table 2). The incidence and longitudinalprevalence of diarrhea among households receiving antibacterial soap was similarto households receiving plain soap.

The mean differences in diarrhea rates between handwashing promotionand control neighborhoods were consistent across most of the individual neighborhoods(Figure 2). Indeed, the diarrheaincidence in 8 of 11 control neighborhoods was higher than in any of the handwashingpromotion neighborhoods.

For the first 8 weeks of the study, the incidence of diarrhea was similaramong children living in handwashing promotion neighborhoods compared withchildren in control neighborhoods. After 8 weeks, the incidence of diarrheaamong children living in handwashing promotion neighborhoods was consistentlylower than children living in control neighborhoods (Figure 3).

Diarrhea was more common among younger children (6.2% longitudinal prevalenceamong infants and 5.5% among children aged 1-2 years) vs older children (3.3%among children aged 2-5 years and 1.1% among children aged 5-15 years). Infantsliving in neighborhoods where handwashing was actively promoted and in householdsthat received plain soap had a 39% lower longitudinal prevalence of diarrhea(95% CI, –61% to –16%) vs infants living in control neighborhoods(Table 3). Children older than5 years living in households that received plain soap had a 57% reductionin diarrhea vs children living in control neighborhoods (95% CI, –73%to –41%). The age-specific longitudinal prevalence of diarrhea amonghouseholds receiving antibacterial soap was similar to households receivingplain soap.

Malnourished children had more diarrhea (5.3% and 4.8% prevalence amongchildren with severe and moderate malnutrition vs 3.7% among children withoutmalnutrition). The effectiveness of soap in preventing diarrhea was independentof childrens' nutritional status. Among children younger than 5 years livingin households that received plain soap and handwashing promotion, those whowere severely malnourished had a 42% lower longitudinal prevalence of diarrhea(95% CI, –69% to –16%) and those who were moderately malnourishedhad a 41% lower longitudinal prevalence (95% CI, –65% to –17%)vs children of comparable age and nutrition status living in control neighborhoods(Table 4). The malnutrition-specificlongitudinal prevalence of diarrhea among households receiving antibacterialsoap was similar to households receiving plain soap.

Compared with control neighborhoods, children living in households thatreceived plain soap and handwashing promotion were 56% less likely to visita health care practitioner for diarrhea (95% CI, –69% to –43%).Hospitalization for diarrhea was uncommon, occurring in only 0.23% of theobserved person-weeks. Children living in households receiving plain soapand handwashing promotion were 26% less likely to be hospitalized for diarrheabut this difference was not statistically significant (95% CI, –100%to 66%). Only 5% of observed episodes of diarrhea were persistent diarrhea(ie, episodes lasting >14 days). Children living in households receiving plainsoap and handwashing promotion were 31% less likely to have a persistent episodeof diarrhea but this difference was not statistically significant (95% CI,–70% to 8%). The probability of visiting a health care practitionerfor diarrhea, being hospitalized for diarrhea, and having a persistent episodeof diarrhea was similar among households receiving antibacterial soap vs householdsreceiving plain soap (Table 5).

Seven children died during the study. For 3 of the children, 1 fromeach of the study groups, the mother reported that the child had diarrheaas part of the illness that led to his/her death. These deaths occurred inchildren aged 33, 36, and 63 months. The diarrhea-specific death rate was1.6 deaths per 1000 children younger than 5 years per year.

In these communities in which diarrhea is the leading cause of childhooddeath, wash water was heavily contaminated with human fecal organisms, andno provisions were made for clean drying of hands, handwashing promotion withsoap halved the burden of diarrheal disease. This study addressed many ofthe methodological concerns raised by previous reviewers of hygiene interventions.^2,20 The intervention was randomly assignedand included a contemporaneous control group. Diarrhea prevalence was similarat the beginning of the study between intervention and control groups. Theanalysis accounted for the cluster design of the intervention and had sufficientpower to evaluate the effectiveness of the intervention in subgroups of childrenat the highest risk of death from diarrhea. The overall level of reductionin longitudinal prevalence of diarrhea among children in households with handwashingpromotion (50% in the plain soap and 46% in the antibacterial soap groups)was remarkably close to the 47% decrease calculated in the recent meta-analysison the effect of handwashing in preventing diarrhea.²

Our study was not designed to evaluate child mortality as an outcome.Only 3 children died from diarrhea during the study, 1 from each group. Ourrate of death from diarrhea was 79% lower than the diarrhea-specific deathrate for children younger than 5 years previously reported from similar communities.¹⁵ The close surveillance for childhood illness by fieldworkers and rapid referral to appropriate clinical care at no cost to thefamily likely contributed to this low death rate.

However, our study did have sufficient power to evaluate the effectivenessof handwashing promotion with soap among children at high risk for death fromdiarrhea. Important risk factors for diarrhea-specific death in developingcountries include age younger than 1 year,^3-6,15 malnutrition,^9-11 and persistent diarrhea.^10,12,13 In our study, infantswho were unable to wash their hands had 39% fewer days of diarrhea if theylived in households that received plain soap and encouragement to wash handscompared with control households. This 39% reduction in diarrhea for infantswas less than the 57% reduction observed among children aged between 5 and15 years who are able to regularly wash their own hands.

Handwashing with soap removes transient potentially pathogenic organismsfrom hands.^21,22 If individualswash their hands, they are less likely to transmit pathogens from their handsto their mouths. This mechanism benefits the person washing his/her handsand is not available to infants. However, persons washing their hands arealso less likely to transfer pathogens from their hands to the hands of others,or to food or the environment that is shared with others. Moreover, parentsand siblings who prevent their own episodes of diarrhea are less likely toshed pathogens to the vulnerable infant's environment. Our study findingssuggest that household handwashing interrupts transmission of diarrheal pathogenssufficiently to markedly reduce diarrhea among infants.

Moderately or severely malnourished children had as large a reductionin diarrhea from improvement in household handwashing as children withoutmalnutrition. Although some reduction in persistent diarrhea (19%-31%) wasobserved within households receiving soap and handwashing promotion, persistentdiarrhea was uncommon and these reductions were not statistically significant.Nevertheless, the effectiveness of handwashing with soap in reducing the longitudinalprevalence of diarrhea among children at increased risk of death from diarrhea—infantsand malnourished children—suggests that handwashing with soap wouldreduce the risk of death from diarrhea.

We found no significant difference in diarrheal disease among personsliving in households receiving antibacterial soap compared with plain soap.This is not surprising because triclocarban is a bacteriostatic agent thatinhibits the growth of some gram-positive bacteria but is not effective againstgram-negative bacteria, viruses, or parasites that cause infectious diarrhea.^23,24

There are important limitations to our study. First, study personneland participants were not blinded to the intervention. It is possible thatstudy participants in the handwashing promotion groups, grateful for the soap,minimized reported episodes of diarrhea in the household, or field workersrecorded fewer episodes because of a desire to meet the expectation of studysponsors. However, field workers were formally trained and the importanceof accurate recording of reported symptoms was stressed. Unannounced supervisoryvisits did not identify systematic errors.

A second limitation was that our study was not originally undertakento evaluate the hypothesis that children at the highest risk of death wouldbenefit from handwashing. We observed more diarrhea than we expected. Diarrheawas unusually prevalent in Karachi in the summer of 2002, both as measuredwithin the study as well as by reports from local clinicians. The incidenceof diarrhea in the control group was more than 3 times higher than in controlgroups we had observed in earlier studies in 2000 and 2001, which we usedto estimate the sample size. We further increased the sample size to assessother outcomes. Thus, sufficient observations for the analysis of diarrheaamong subgroups at high risk of death were recorded. The analysis and reportingof interesting subgroups risks publication bias. However, the reduction indiarrheal disease noted among infants and malnourished children was not statisticallyborderline. Moreover, there were 2 intervention groups, plain soap and antibacterialsoap, and the findings from both suggest a consistent phenomena.

A third limitation was that all of the disease reduction in the interventioncommunities was not necessarily attributable to improved handwashing. It ispossible that regular visits by field workers, the provision of soap, andthe successful improvement in hand hygiene led to other behavioral changesin households that reduced diarrheal disease. However, the high soap consumptionof families suggests frequent handwashing and field workers were specificallytrained to limit behavioral change messages to handwashing promotion. Thus,improved handwashing likely played an important role in reducing the incidenceof diarrhea.

Although visiting households weekly to provide free soap and encouragehandwashing was effective in reducing diarrhea, this approach is prohibitivelyexpensive for widespread implementation. The next essential step is to developeffective approaches to promote handwashing that cost less and can be usedto reach millions of at-risk households. Studies evaluating the durabilityof behavioral change from handwashing promotion are also important to assesscost-effectiveness. In the interim, existing public health programs shouldexperiment with integrating handwashing promotion into their current activities.