Background
In a low-income country like Bangladesh, where the poverty rate is higher in rural compared to urban areas, the consistent use of sanitary latrines over time is a challenge. To address this issue, the Water, Sanitation, and Hygiene (WASH) program of the Bangladesh Rural Advancement Committee (BRAC) was devised to improve health of the rural poor through enhanced sanitation services, such as by providing loans or education. Sanitary latrine use in households and changes over time were assessed in this study.

Methods
This was a longitudinal cohort study of the baseline, midline, and end line status of the WASH project. Households assessed in all three rounds of surveys (26,404 in each survey) were included in the analysis. Thirty thousand households from 50 upazilas (sub-districts) were selected in two stages: i) thirty villages were selected from each of the 50 upazilas by cluster sampling, and ii) twenty households were chosen systematically from each selected village. A female member capable of providing household-level information was interviewed from each house using the pre-tested questionnaire. Spot observations of some components were made to assess the quality of sanitary latrine use. The adjusted log-binomial regression was performed and risk ratios with 95% confidence intervals were estimated for sanitary latrine use. Data were analyzed using Statistical Package for the Social Sciences (SPSS) and Stata software.

Results
The use of sanitary latrines by households increased significantly from the baseline (31.7%) to midline (41.5%) and end line (57.4%) assessment points. The proportion of physically verified clean latrines increased significantly from 33.4% at baseline to 50.8% at the midline and 53.3% at the end line. Analysis of changes in latrine-use showed that 73.3% of the baseline latrine-using households continued to do so at the end line, while the rest switched to unsanitary practices. Households with better socioeconomic status were more likely to use sanitary latrines.

Conclusion
There are improvements in ownership and use of sanitary latrines by households over the years in WASH intervention areas. However, switching of some households from sanitary to unsanitary latrines remains a matter of concern regarding sustainability.