Sub-daily weather conditions and drowning in West Bengal, India: a case-crossover study using hourly meteorological data

Drowning is a major cause of injury mortality in low and middle-income countries, yet there is little evidence about the relationship between drowning and short-term weather related risk. This study examined associations between sub-daily meteorological conditions and drowning in West Bengal, India, using a time-stratified case-crossover design. Of 2,414 eligible drowning events, 1,696 fatal events had complete data. Weather during the reported event-time period, derived from hourly ERA5-Land data, was compared with matched periods at the same time of day, on the same day of the week and in the same calendar month. In the primary multivariable model, temperature showed a positive, although not statistically significant, association with fatal drowning (OR 1.034 per 1°C, 95% CI 0.998-1.072), while wind speed, precipitation and relative humidity showed little evidence of association. Natural-spline analysis supported a non-linear association for wind speed (p = 0.003). Exploratory prior-day analyses suggested lower drowning odds with higher wind speed two and three days before the event, while most extreme-weather indicators showed little association with fatal drowning. Overall, primary analyses provided limited evidence of immediate linear weather effects, while secondary analyses suggest non-linear wind and recent-weather patterns that warrant further exploration.