1. Introduction
Diarrhea is a leading cause of death among children under five years of age (U5), especially in low- and lower middle-income countries [
1,
2]. According to the World Health Organization, approximately 525,000 children U5 die from diarrheal disease each year [
3]. Lao People’s Democratic Republic (PDR) is a lower middle-income country located in Southeast Asia. In Lao PDR, the mortality rate of children U5 remains high compared to those in neighboring countries such as Thailand, Vietnam, and Cambodia, which is due partly to diarrhea [
4,
5,
6]. The Global Burden of Diseases Diarrhoeal Diseases Collaborators estimated that the mortality of diarrheal disease in children U5 was 97.1/100,000, and approximately 1,000,000 episodes occurred in children U5 in Lao PDR in 2015 [
7].
Hand-washing in everyday life is effective for reducing the risk of diarrhea. A systematic review examined the impact of hand-washing with soap on the risk of diarrheal disease and reported that hand-washing with soap in community settings can reduce the risk of diarrheal disease by 42–47%; therefore, interventions to promote hand-washing can save millions of lives a year [
8]. According to another systematic review that assessed the effects of hand-washing promotion interventions on childhood diarrhea, community-based hand-washing promotion in low- and middle-income countries can reduce the incidence of diarrhea in children by approximately a quarter [
9].
Rapid observations are widely used as a proxy measure of hand-washing practice, assuming that household members practice hand-washing with soap if a specific place for hand-washing is observed in a household with available water and soap [
10]. In a nationwide survey, such as the Multiple Indicator Cluster Survey and the Demographic and Health Survey, rapid observations are widely adopted, since it can be challenging to measure hand-washing practice by direct observation because of the enormous associated costs and times. The Lao Social Indicator Survey II (LSIS II), a household-based nationwide survey that was implemented by the Lao government in 2017, also used rapid observations.
In Lao PDR, expanding the coverage of water, sanitation, and hygiene (WASH) facilities has been prioritized especially in rural areas and many WASH projects including open defecation free projects have been implemented [
11]. However, very few projects measured project’s impact on health outcomes including diarrhea. A comprehensive WASH in school project, which included water supply, sanitation, hand-washing, and behavior change interventions, was implemented in 492 primary schools across 13 provinces between 2013 and 2017 [
12]. A cluster randomized controlled trial study was done in Saravan province to measure the project’s impact on pupil absence, diarrhea, respiratory infection, and soil-transmitted helminth infection. The study found, however, that even among schools with the high level of fidelity and adherence, impact of the intervention was minimal. Thus, the study concluded that WASH in school alone may not achieve significant health gains without concurrent community and household WASH improvements including the improvement of hand-washing [
13].
The association between hand-washing facilities with soap and diarrhea incidence among children U5 remains poorly understood in Lao PDR. To the best of our knowledge, two studies have assessed this association in Lao PDR. A cross-sectional study with 297 households in 50 villages in Saravan province examined associations between the presence of household hand-washing facilities and the infection status of diarrhea-causing pathogens among household members, including children U5 [
14]. The study found that the presence of household hand-washing facilities was associated with lower infection rates of viral enteric pathogens and soil-transmitted helminths among household members. Another longitudinal study assessed diarrheal risk factors with 234 households from two villages in Saravan province, including all household members [
15]. The study found that the presence of hand-washing with soap near or in the toilet was not associated with self-reported diarrhea episodes. The LSIS II included both rapid observation of the hand-washing facilities with soap and diarrhea episodes in children U5 [
4]. However, no analysis has been made on the association.
Therefore, the present study aimed to assess the association between the presence of household hand-washing facilities with water and soap and diarrhea episodes among children U5 in Lao PDR using data from the LSIS II. We have long conducted research concerning community health in rural Lao PDR. The present study was conducted as a part of a larger study that aims to inform strategies to promote hand-washing with soap in rural Lao PDR.
4. Discussion
The main finding of the present study was that children whose households possess hand-washing facilities with both water and soap were significantly less likely to experience diarrhea episodes compared to children whose households possess hand-washing facilities with water alone. This finding suggests that in the Lao setting, hand-washing with soap is more effective for preventing childhood diarrhea episodes compared to hand-washing without soap. This finding is important because hand-washing facilities with water are available in most households in Lao PDR. If soap use becomes more common, the mortality and morbidity due to diarrhea could be widely reduced.
This main finding is biologically plausible. Analysis of the samples collected at Lao healthcare facilities showed that the major etiologic agents of acute childhood diarrhea are rotavirus,
Escherichia coli, and
Salmonella spp. [
22], which are transmitted from person-to-person via contaminated hands in households. A community-based study involving 1159 households in rural Lao PDR showed that enteropathogen infections are strongly correlated within members of the same household, suggesting the importance of intra-household transmission [
14]. A randomized controlled trial with volunteers in the U.K. showed that hand-washing with plain soap is more effective for the removal of bacterial pathogens from hands than hand-washing with water alone [
23]. A community-based randomized control trial with mothers in Bangladesh also showed that hand-washing with a bar of soap is more effective for reducing the bacterial load of coliforms and
Clostridium perfringens compared to hand-washing with water alone [
24]. Additionally, an experimental study with volunteers in the U.S. showed that hand-washing with hand soap and water is effective for reducing viral contamination from finger pads [
25].
The main finding is also consistent with those reported from similar observational studies. A cross-sectional study involving 347 households in rural Bangladesh showed that children U5 whose family members washed their hands with soap after defecation were significantly less likely to experience a diarrhea episode in the 48 h preceding the survey compared to children whose family members washed their hands with water only [
26]. A cross-sectional study in Malawi, which used Demographic and Health Survey data, showed that the lack of soap in hand-washing facilities was associated with higher odds of having a diarrhea episode among children U5 [
27]. In contrast, the main finding of the present study is not consistent with the findings of a study conducted in Saravan province of the Lao PDR. There are two possible reasons for this inconsistency: first, the Saravan study used all household member’s diarrhea episodes as the outcome, suggesting that the reason for the discrepancy could be due to methodological differences. Second, the Saravan study included only 46 diarrhea cases as the outcome, suggesting that the study likely suffered from type II errors; i.e., false negatives.
Although the effect of soap being present in hand-washing facilities on diarrhea incidence was not large (i.e., 5.9% among children in households with soap vs. 8.1% among children in households without soap), placing soap in hand-washing facilities could widely impact the health of Lao children, as more than one-third of Lao households do not have soap in their hand-washing facilities. Based on the assumption that a household has one child U5, 283,000 out of the total 786,000 children U5 in Lao could benefit from placing soap in hand-washing facilities. Additionally, the use of soap could contribute to preventing not only diarrhea, but also other illnesses including pneumonia, which is also a leading cause of death among Lao children [
6,
28].
The reasons for the absence of soap in hand-washing facilities in many households remain poorly understood in Lao PDR, as no study has been conducted in the country to explore these reasons. The LSIS II report showed, however, that there are some household trends for the absence of soap in handwashing facilities: rural households, households whose heads have lower educational attainment, households of lower wealth quintiles, and households of minority language groups are less likely to have soap in their hand-washing facilities compared to their counterparts [
4]. A study on hand-washing facilities in 51 countries reported similar trends: universally, households of higher wealth quintiles and urban households are more likely to have soap in their hand-washing facilities, compared to their counterparts [
29]. In Lao PDR, however, soap seems to be affordable for many people: the average price of a bar of soap was 3110 kip (approximately 0.34 U.S. dollars) in 2017 [
30]. Considering these trends and the price of soap, further study is necessary to identify the barriers to placing soap in hand-washing facilities in Lao PDR.
The results of the present study also showed that there was no significant difference in the incidence of diarrhea between households with hand-washing facilities where soap and water are available and households without hand-washing facilities. A possible explanation for the lack of a difference is that the households without hand-washing facilities include a substantial proportion of households that live near a community well, and thus household members use the community well as a hand-washing facility. A community-shared well is commonly seen in rural villages of Lao PDR. In fact, wells are a major source of water for housework, including hand-washing, in rural Lao PDR [
4]. Additionally, according to the LSIS II survey, in the 66.7% of households their toilet facilities were located not in their houses but in their yards. Thus, there is a possibility that household members have little difficulty in using a community well after defecation, if they live near a community well.
Likewise, in the present study there was no significant difference in the incidence of diarrhea between households with improved sanitation facility and households with no sanitation facility. Currently, we are unable to provide a possible reason for the lack of a difference. A multi-country case control study, which assessed sanitation and hygiene-specific risk factors for moderate-to-severe childhood diarrhea, also showed that there was no significant difference in the risk of diarrhea between households with private sanitation facilities and households with no sanitation facility in, for example, Bangladesh [
31]. However, the case-control study did not provide any possible reasons.
A major limitation of the present study is the absence of information about actual hand-washing practices. It is of concern whether the study participants of the households where soap is available in hand-washing facilities actually use soap, as studies have shown that in settings where soap is available, people do not necessarily use soap when washing their hands before/after critical events such as fecal contact, food preparation, eating, and feeding a child. A school-based study in Lao PDR observed that of the pupils who used the school toilet, only 23.9% washed their hands with soap afterward [
12]. A multi-country study that evaluated the validity of rapid observation measures of hand-washing practices concluded that the observation of hand-washing materials in hand-washing facilities is a valid measure of hand-washing with soap, although the use of soap is often suboptimal: 27–82% of the primary caretakers of children U5 used soap after possible fecal contact, and overall, they used soap before 24–36% of critical events [
32].
Another limitation is that the present study was not able to incorporate all the factors which are reported to be associated with childhood diarrhea episodes in similar studies. Such factors include food preparation practices and child feces disposal practices. For example, a cross-sectional study in Viet Nam showed that the risk of childhood diarrhea was significantly higher among children whose mothers prepared food for cooking somewhere other than the table, compared to children whose mothers prepared food on the table [
33]. A cross-sectional study using the data of the 2013 Nigerian Demographic and Health Survey reported that the increased risk of childhood diarrhea was significantly associated with unsafe child feces disposal practices of caretakers [
16].
In order to maximize the effect of hand-washing on preventing communicable diseases, merely recommending hand-washing with soap before/after critical events is not enough. The Centers for Disease Control and Prevention recommends the five steps for domestic hand-washing: wetting hands with clean, running water; lathering hands by rubbing hands together with soap; scrubbing hands for at least 20 s; rinsing hands well under clean, running water; and drying hands using a clean towel or air dry hands [
34]. A community-based study with primary caregivers of school children in Zimbabwe demonstrated the importance of these five steps in removing microbial contamination [
35]. A health education intervention study in Hong Kong showed that the five-steps hand hygiene technique was effective in reducing the spread of infectious diseases in the special education school setting [
36]. Because children learn hand-washing from their primary caretakers whose hand hygiene practices are sometimes suboptimal [
37,
38], health education interventions on hand hygiene to children and caretakers are recommended to promote effective hand-washing.
The results of the present study showed that most of the households with children U5 already had improved sanitation facilities (70.2%) and improved source of drinking water (82.2%), whereas only 49.1% of the households with children U5 had hand-washing facilities with water and soap. The results suggest that hygiene education does not keep up with the increased coverage of sanitation and water supply. Therefore, more efforts should be made in promoting hygiene education in Lao PDR. The proportion of the population that use hand-washing facilities with water and soap is one of the indicators for Target 6.2 of Sustainable Development Goal 6: “By 2030, achieve access to adequate and equitable sanitation and hygiene for all and end open defecation, paying special attention to the needs of women and girls and those in vulnerable situations” [
39]. The present study showed that the proportion of households using hand-washing facilities with water and soap is 49.1%, suggesting that continued efforts are needed to achieve Target 6.2 in Lao PDR. In 2017, globally, 60% of the population had basic hand-washing facilities with water and soap, whereas 22% had limited hand-washing facilities lacking water and/or soap [
40]. Therefore, many countries, including Lao PDR, face the same challenge: trying to increase the population using basic hand-washing facilities with water and soap.