Table 3. Subgroup analyses.
Study wards were stratified according to several criteria likely related to the rural-urban status of the community. The incidence of corneal opacity is shown for each treatment group across each stratum, along with the incidence rate ratio for the stratum (ward-level analyses).
| Incidence Rate (95%CI) | |||||
|---|---|---|---|---|---|
| Subgroup | Wards | Intervention | Control | Incidence Rate Ratio (95%CI) | Interaction P-valuea |
| Elevationb | 0.34 | ||||
| Low (< 300 m) | 168 | 1.16 (0.81–1.65) | 0.98 (0.65–1.48) | 1.17 (0.68–2.02) | |
| High (≥ 300 m) | 48 | 1.28 (0.95–1.73) | 1.79 (0.77–4.12) | 0.72 (0.30–1.75) | |
| Population densityc | 0.02 | ||||
| Above median | 108 | 1.13 (0.78–1.63) | 0.72 (0.51–1.01) | 1.57 (0.95–2.60) | |
| Below median | 108 | 1.23 (0.95–1.59) | 1.72 (1.01–2.92) | 0.72 (0.40–1.29) | |
| Distance from roadd | 0.04 | ||||
| Close (< 3 km) | 128 | 1.34 (0.90–1.98) | 0.94 (0.69–1.28) | 1.43 (0.87–2.36) | |
| Far (≥ 3 km) | 88 | 1.00 (0.70–1.42) | 1.85 (0.85–4.05) | 0.54 (0.23–1.28) | |
| Local classificatione | 0.04 | ||||
| Urban or peri-urban | 182 | 1.15 (0.85–1.57) | 0.88 (0.66–1.17) | 1.31 (0.86–1.99) | |
| Rural | 34 | 1.43 (0.94–2.18) | 2.88 (1.21–6.81) | 0.50 (0.19–1.30) | |
Interaction of study arm (intervention vs control) by subgroup in negative binomial regression of ward-level data with robust standard errors to account for village-level clustering
Extracted with R package elevatr for each household using baseline global positioning system (GPS) coordinates; summarized as a ward-level mean. Communities at higher elevation would be expected to be more rural.
Estimated for each household as the average distance to its 10 nearest neighbors, using GPS data from the baseline census; summarized as a ward-level mean. Communities with greater population density would be expected to be more rural.
Distance from the East-West Highway, a major urbanized thoroughfare in Nepal. Estimated for each household using baseline GPS data; wards in which all households were within 3km were classified as close, and the remaining as far. Communities farther from the road would be expected to be more rural.
Classified for internal study purposes based on the opinions of local study staff who visited communities as part of the study and were masked to study results.