Effect of a sanitation intervention on the nutritional status of children in Maputo, Mozambique: a controlled before-and-after trial

This controlled before-and-after trial in Maputo, Mozambique, found no significant evidence that a shared onsite sanitation intervention improved child nutritional status, specifically stunting or underweight, over a 24-month period.

The Gist

Imagine a bustling city like Maputo, Mozambique, is a giant, crowded house where many families live on top of each other in small, makeshift rooms. In these tight spaces, there's a big problem: poverty, too many people, and no safe toilets. It's like trying to grow a healthy garden in a pot that's filled with dirty water and trash; the plants (the children) just can't get the nutrients they need to grow tall and strong.

This study was like a scientific experiment to see if fixing the toilets would help the plants grow.

The Experiment: A New Toilet Plan

The researchers decided to test a specific solution: building shared, clean toilets right where the families live. They wanted to see if this "plumbing upgrade" would stop children from getting sick and malnourished.

• The Test Group: They picked a bunch of neighborhoods and gave them these new shared toilets.
• The Control Group: They picked similar neighborhoods nearby but didn't give them new toilets yet, just to see what would happen without the upgrade.
• The Timeline: They checked on the kids at the start, then again one year later, and finally two years later. They looked at three main things:
  1. Stunting: Is the child too short for their age? (Like a sapling that never grew tall).
  2. Wasting: Is the child too thin? (Like a wilting leaf).
  3. Underweight: Is the child too light overall?

What They Found: The Surprising Result

You might expect that giving people clean toilets would be like giving a thirsty plant a fresh hose of water—immediate growth! But the results were a bit more complicated.

• The Big Picture: For the most part, the new toilets didn't make a noticeable difference in how tall or heavy the children were after one or two years. The "garden" didn't suddenly bloom just because the toilets were fixed.
• The Tiny Glimmer: There was a very faint hint that the new toilets might have helped with "wasting" (thinness), but the evidence was so weak it was like seeing a shadow and guessing it's a person. It wasn't a clear win.
• The "What If" Scenarios: The researchers did some extra detective work (exploratory analyses):
  • When they looked only at babies born after the toilets were built, the kids in the new-toilet group actually got shorter (more stunting) compared to the others.
  • When they removed the control families who secretly fixed their own toilets during the study, the new-toilet group seemed to have less thinness (wasting).

The Takeaway: It's Not Just About the Toilets

Think of a child's health like a three-legged stool. You need good food, good healthcare, and good sanitation to keep it balanced. This study suggests that fixing just the "sanitation leg" isn't enough to make the stool stand up straight in these crowded, poor neighborhoods.

The researchers concluded that while clean toilets are important, they aren't a magic wand. In complex, crowded cities, you can't just fix the plumbing and expect the children to instantly grow taller. There are other hidden factors—like what the kids are eating or how sick they get from other sources—that are also pulling the stool down.

In short: We tried to fix the toilets to help the kids grow, and while it didn't fail completely, it didn't work the way we hoped. We need to look at the whole picture, not just the bathroom, to solve the problem of hungry, undernourished children in cities.

Technical Summary

Technical Summary: Effect of a Sanitation Intervention on Child Nutritional Status in Maputo, Mozambique

1. Problem Statement

Rapid urbanization has led to the proliferation of informal urban settlements globally, characterized by high population density, poverty, and a critical lack of safe sanitation. These conditions create heightened health risks for vulnerable populations, particularly young children. While the link between sanitation and diarrheal disease is well-established, the specific impact of sanitation interventions on childhood nutritional status (stunting, wasting, and underweight) in complex, high-density urban environments remains less understood. This study addresses the gap in evidence regarding whether shared, onsite sanitation improvements can effectively reduce undernutrition in such settings.

2. Methodology

The study, known as the Maputo Sanitation (MapSan) trial, was designed as a controlled before-and-after study (a quasi-experimental design) rather than a randomized controlled trial.

• Setting: Informal urban settlements in Maputo, Mozambique.
• Intervention: Implementation of shared, onsite sanitation facilities.
• Study Population: Children aged 1 to 48 months at baseline.
  • Intervention Group: 757 children enrolled.
  • Control Group: 852 children enrolled in comparable compounds without the intervention.
• Data Collection: Outcomes were measured at three time points: baseline (pre-intervention), 12 months post-intervention, and 24 months post-intervention.
• Primary Outcomes:
  • Prevalence of stunting (height-for-age), wasting (weight-for-height), and underweight (weight-for-age).
  • Z-scores for height-for-age (HAZ), weight-for-height (WHZ), and weight-for-age (WAZ).
• Analysis Strategy: The primary analysis followed an intention-to-treat (ITT) principle. The study was registered at ClinicalTrials.gov (NCT02362932).

3. Key Contributions

• Contextual Evidence: Provides rare, rigorous longitudinal data on sanitation interventions specifically within informal urban settlements, a setting often excluded from rural-focused sanitation studies.
• Longitudinal Design: Unlike cross-sectional studies, this trial tracked the same cohorts over a 24-month period, allowing for the assessment of both immediate and sustained effects of the intervention.
• Exploratory Sub-analyses: The study went beyond the primary ITT analysis to explore specific subgroups:
  1. Children born into compounds after the intervention was implemented.
  2. A sensitivity analysis excluding control compounds that had independently improved their sanitation facilities during the follow-up period.

4. Results

The primary analysis yielded null results for most nutritional indicators:

• Stunting and Underweight: There was no statistical evidence of an effect on stunting or underweight at either the 12-month or 24-month follow-up points.
• Wasting: The primary analysis showed no significant effect, though there was "very weak evidence" of a potential benefit (Adjusted Prevalence Ratio: 0.497; 95% CI: 0.22–1.11; p=0.09).

Exploratory Findings:
When analyzing specific subgroups, the results diverged from the primary analysis:

• In the subgroup of children born post-intervention and in the analysis excluding control compounds with independent sanitation upgrades, the data suggested a decrease in wasting but a paradoxical increase in stunting within the intervention group.
• These conflicting signals in the exploratory analyses highlight the complexity of isolating sanitation effects in dynamic urban environments where multiple confounding factors (e.g., independent infrastructure improvements in control groups) are at play.

5. Significance and Conclusion

The MapSan trial contributes significantly to the discourse on the Sanitation-Hypothesis regarding child nutrition.

• Main Conclusion: The study found no evidence that a shared, onsite sanitation intervention reduced stunting or underweight, and only weak evidence for a reduction in wasting in the general population of informal settlements in Maputo.
• Implications: The findings suggest that in complex urban environments, sanitation improvements alone may be insufficient to reverse childhood undernutrition. The lack of effect may be due to the multifactorial nature of malnutrition (e.g., dietary intake, maternal health, other environmental pathogens) or the specific challenges of implementing shared facilities in high-density informal settlements.
• Future Directions: The authors emphasize the need for further research to understand the mechanisms through which sanitation interacts with other determinants of health in urban settings to effectively reduce childhood undernutrition.